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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fix from Steven Rostedt:
"The newly added ftrace_print_array_seq() function had a bug in it.
Luckily, the only user of it didn't make the 4.1 merge window.
But the helper function should be fixed before 4.2 when the users
start coming in"
* tag 'trace-fixes-v4.1-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Make ftrace_print_array_seq compute buf_len
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block plug callback could sleep, so we introduce a parameter
'from_schedule' and corresponding drivers can use it to destinguish a
schedule plug flush or a plug finish. Unfortunately io_schedule_out
still uses blk_flush_plug(). This causes below output (Note, I added a
might_sleep() in raid1_unplug to make it trigger faster, but the whole
thing doesn't matter if I add might_sleep). In raid1/10, this can cause
deadlock.
This patch makes io_schedule_out always uses blk_schedule_flush_plug.
This should only impact drivers (as far as I know, raid 1/10) which are
sensitive to the 'from_schedule' parameter.
[ 370.817949] ------------[ cut here ]------------
[ 370.817960] WARNING: CPU: 7 PID: 145 at ../kernel/sched/core.c:7306 __might_sleep+0x7f/0x90()
[ 370.817969] do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff81092fcf>] prepare_to_wait+0x2f/0x90
[ 370.817971] Modules linked in: raid1
[ 370.817976] CPU: 7 PID: 145 Comm: kworker/u16:9 Tainted: G W 4.0.0+ #361
[ 370.817977] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140709_153802- 04/01/2014
[ 370.817983] Workqueue: writeback bdi_writeback_workfn (flush-9:1)
[ 370.817985] ffffffff81cd83be ffff8800ba8cb298 ffffffff819dd7af 0000000000000001
[ 370.817988] ffff8800ba8cb2e8 ffff8800ba8cb2d8 ffffffff81051afc ffff8800ba8cb2c8
[ 370.817990] ffffffffa00061a8 000000000000041e 0000000000000000 ffff8800ba8cba28
[ 370.817993] Call Trace:
[ 370.817999] [<ffffffff819dd7af>] dump_stack+0x4f/0x7b
[ 370.818002] [<ffffffff81051afc>] warn_slowpath_common+0x8c/0xd0
[ 370.818004] [<ffffffff81051b86>] warn_slowpath_fmt+0x46/0x50
[ 370.818006] [<ffffffff81092fcf>] ? prepare_to_wait+0x2f/0x90
[ 370.818008] [<ffffffff81092fcf>] ? prepare_to_wait+0x2f/0x90
[ 370.818010] [<ffffffff810776ef>] __might_sleep+0x7f/0x90
[ 370.818014] [<ffffffffa0000c03>] raid1_unplug+0xd3/0x170 [raid1]
[ 370.818024] [<ffffffff81421d9a>] blk_flush_plug_list+0x8a/0x1e0
[ 370.818028] [<ffffffff819e3550>] ? bit_wait+0x50/0x50
[ 370.818031] [<ffffffff819e21b0>] io_schedule_timeout+0x130/0x140
[ 370.818033] [<ffffffff819e3586>] bit_wait_io+0x36/0x50
[ 370.818034] [<ffffffff819e31b5>] __wait_on_bit+0x65/0x90
[ 370.818041] [<ffffffff8125b67c>] ? ext4_read_block_bitmap_nowait+0xbc/0x630
[ 370.818043] [<ffffffff819e3550>] ? bit_wait+0x50/0x50
[ 370.818045] [<ffffffff819e3302>] out_of_line_wait_on_bit+0x72/0x80
[ 370.818047] [<ffffffff810935e0>] ? autoremove_wake_function+0x40/0x40
[ 370.818050] [<ffffffff811de744>] __wait_on_buffer+0x44/0x50
[ 370.818053] [<ffffffff8125ae80>] ext4_wait_block_bitmap+0xe0/0xf0
[ 370.818058] [<ffffffff812975d6>] ext4_mb_init_cache+0x206/0x790
[ 370.818062] [<ffffffff8114bc6c>] ? lru_cache_add+0x1c/0x50
[ 370.818064] [<ffffffff81297c7e>] ext4_mb_init_group+0x11e/0x200
[ 370.818066] [<ffffffff81298231>] ext4_mb_load_buddy+0x341/0x360
[ 370.818068] [<ffffffff8129a1a3>] ext4_mb_find_by_goal+0x93/0x2f0
[ 370.818070] [<ffffffff81295b54>] ? ext4_mb_normalize_request+0x1e4/0x5b0
[ 370.818072] [<ffffffff8129ab67>] ext4_mb_regular_allocator+0x67/0x460
[ 370.818074] [<ffffffff81295b54>] ? ext4_mb_normalize_request+0x1e4/0x5b0
[ 370.818076] [<ffffffff8129ca4b>] ext4_mb_new_blocks+0x4cb/0x620
[ 370.818079] [<ffffffff81290956>] ext4_ext_map_blocks+0x4c6/0x14d0
[ 370.818081] [<ffffffff812a4d4e>] ? ext4_es_lookup_extent+0x4e/0x290
[ 370.818085] [<ffffffff8126399d>] ext4_map_blocks+0x14d/0x4f0
[ 370.818088] [<ffffffff81266fbd>] ext4_writepages+0x76d/0xe50
[ 370.818094] [<ffffffff81149691>] do_writepages+0x21/0x50
[ 370.818097] [<ffffffff811d5c00>] __writeback_single_inode+0x60/0x490
[ 370.818099] [<ffffffff811d630a>] writeback_sb_inodes+0x2da/0x590
[ 370.818103] [<ffffffff811abf4b>] ? trylock_super+0x1b/0x50
[ 370.818105] [<ffffffff811abf4b>] ? trylock_super+0x1b/0x50
[ 370.818107] [<ffffffff811d665f>] __writeback_inodes_wb+0x9f/0xd0
[ 370.818109] [<ffffffff811d69db>] wb_writeback+0x34b/0x3c0
[ 370.818111] [<ffffffff811d70df>] bdi_writeback_workfn+0x23f/0x550
[ 370.818116] [<ffffffff8106bbd8>] process_one_work+0x1c8/0x570
[ 370.818117] [<ffffffff8106bb5b>] ? process_one_work+0x14b/0x570
[ 370.818119] [<ffffffff8106c09b>] worker_thread+0x11b/0x470
[ 370.818121] [<ffffffff8106bf80>] ? process_one_work+0x570/0x570
[ 370.818124] [<ffffffff81071868>] kthread+0xf8/0x110
[ 370.818126] [<ffffffff81071770>] ? kthread_create_on_node+0x210/0x210
[ 370.818129] [<ffffffff819e9322>] ret_from_fork+0x42/0x70
[ 370.818131] [<ffffffff81071770>] ? kthread_create_on_node+0x210/0x210
[ 370.818132] ---[ end trace 7b4deb71e68b6605 ]---
V2: don't change ->in_iowait
Cc: NeilBrown <neilb@suse.de>
Signed-off-by: Shaohua Li <shli@fb.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
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The module notifier call chain for MODULE_STATE_COMING was moved up before
the parsing of args, into the complete_formation() call. But if the module failed
to load after that, the notifier call chain for MODULE_STATE_GOING was
never called and that prevented the users of those call chains from
cleaning up anything that was allocated.
Link: http://lkml.kernel.org/r/554C52B9.9060700@gmail.com
Reported-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Fixes: 4982223e51e8 "module: set nx before marking module MODULE_STATE_COMING"
Cc: stable@vger.kernel.org # 3.16+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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This patch adds the necessary Xen specific code to allow Xen to
support the CPU halting and kicking operations needed by the queue
spinlock PV code.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-12-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This patch adds the necessary KVM specific code to allow KVM to
support the CPU halting and kicking operations needed by the queue
spinlock PV code.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-11-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Provide a separate (second) version of the spin_lock_slowpath for
paravirt along with a special unlock path.
The second slowpath is generated by adding a few pv hooks to the
normal slowpath, but where those will compile away for the native
case, they expand into special wait/wake code for the pv version.
The actual MCS queue can use extra storage in the mcs_nodes[] array to
keep track of state and therefore uses directed wakeups.
The head contender has no such storage directly visible to the
unlocker. So the unlocker searches a hash table with open addressing
using a simple binary Galois linear feedback shift register.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1429901803-29771-9-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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When we detect a hypervisor (!paravirt, see qspinlock paravirt support
patches), revert to a simple test-and-set lock to avoid the horrors
of queue preemption.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Currently, atomic_cmpxchg() is used to get the lock. However, this
is not really necessary if there is more than one task in the queue
and the queue head don't need to reset the tail code. For that case,
a simple write to set the lock bit is enough as the queue head will
be the only one eligible to get the lock as long as it checks that
both the lock and pending bits are not set. The current pending bit
waiting code will ensure that the bit will not be set as soon as the
tail code in the lock is set.
With that change, the are some slight improvement in the performance
of the queued spinlock in the 5M loop micro-benchmark run on a 4-socket
Westere-EX machine as shown in the tables below.
[Standalone/Embedded - same node]
# of tasks Before patch After patch %Change
---------- ----------- ---------- -------
3 2324/2321 2248/2265 -3%/-2%
4 2890/2896 2819/2831 -2%/-2%
5 3611/3595 3522/3512 -2%/-2%
6 4281/4276 4173/4160 -3%/-3%
7 5018/5001 4875/4861 -3%/-3%
8 5759/5750 5563/5568 -3%/-3%
[Standalone/Embedded - different nodes]
# of tasks Before patch After patch %Change
---------- ----------- ---------- -------
3 12242/12237 12087/12093 -1%/-1%
4 10688/10696 10507/10521 -2%/-2%
It was also found that this change produced a much bigger performance
improvement in the newer IvyBridge-EX chip and was essentially to close
the performance gap between the ticket spinlock and queued spinlock.
The disk workload of the AIM7 benchmark was run on a 4-socket
Westmere-EX machine with both ext4 and xfs RAM disks at 3000 users
on a 3.14 based kernel. The results of the test runs were:
AIM7 XFS Disk Test
kernel JPM Real Time Sys Time Usr Time
----- --- --------- -------- --------
ticketlock 5678233 3.17 96.61 5.81
qspinlock 5750799 3.13 94.83 5.97
AIM7 EXT4 Disk Test
kernel JPM Real Time Sys Time Usr Time
----- --- --------- -------- --------
ticketlock 1114551 16.15 509.72 7.11
qspinlock 2184466 8.24 232.99 6.01
The ext4 filesystem run had a much higher spinlock contention than
the xfs filesystem run.
The "ebizzy -m" test was also run with the following results:
kernel records/s Real Time Sys Time Usr Time
----- --------- --------- -------- --------
ticketlock 2075 10.00 216.35 3.49
qspinlock 3023 10.00 198.20 4.80
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-7-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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When we allow for a max NR_CPUS < 2^14 we can optimize the pending
wait-acquire and the xchg_tail() operations.
By growing the pending bit to a byte, we reduce the tail to 16bit.
This means we can use xchg16 for the tail part and do away with all
the repeated compxchg() operations.
This in turn allows us to unconditionally acquire; the locked state
as observed by the wait loops cannot change. And because both locked
and pending are now a full byte we can use simple stores for the
state transition, obviating one atomic operation entirely.
This optimization is needed to make the qspinlock achieve performance
parity with ticket spinlock at light load.
All this is horribly broken on Alpha pre EV56 (and any other arch that
cannot do single-copy atomic byte stores).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-6-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This is a preparatory patch that extracts out the following 2 code
snippets to prepare for the next performance optimization patch.
1) the logic for the exchange of new and previous tail code words
into a new xchg_tail() function.
2) the logic for clearing the pending bit and setting the locked bit
into a new clear_pending_set_locked() function.
This patch also simplifies the trylock operation before queuing by
calling queued_spin_trylock() directly.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-5-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Because the qspinlock needs to touch a second cacheline (the per-cpu
mcs_nodes[]); add a pending bit and allow a single in-word spinner
before we punt to the second cacheline.
It is possible so observe the pending bit without the locked bit when
the last owner has just released but the pending owner has not yet
taken ownership.
In this case we would normally queue -- because the pending bit is
already taken. However, in this case the pending bit is guaranteed
to be released 'soon', therefore wait for it and avoid queueing.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-4-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This patch introduces a new generic queued spinlock implementation that
can serve as an alternative to the default ticket spinlock. Compared
with the ticket spinlock, this queued spinlock should be almost as fair
as the ticket spinlock. It has about the same speed in single-thread
and it can be much faster in high contention situations especially when
the spinlock is embedded within the data structure to be protected.
Only in light to moderate contention where the average queue depth
is around 1-3 will this queued spinlock be potentially a bit slower
due to the higher slowpath overhead.
This queued spinlock is especially suit to NUMA machines with a large
number of cores as the chance of spinlock contention is much higher
in those machines. The cost of contention is also higher because of
slower inter-node memory traffic.
Due to the fact that spinlocks are acquired with preemption disabled,
the process will not be migrated to another CPU while it is trying
to get a spinlock. Ignoring interrupt handling, a CPU can only be
contending in one spinlock at any one time. Counting soft IRQ, hard
IRQ and NMI, a CPU can only have a maximum of 4 concurrent lock waiting
activities. By allocating a set of per-cpu queue nodes and used them
to form a waiting queue, we can encode the queue node address into a
much smaller 24-bit size (including CPU number and queue node index)
leaving one byte for the lock.
Please note that the queue node is only needed when waiting for the
lock. Once the lock is acquired, the queue node can be released to
be used later.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-2-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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In up_write()/up_read(), rwsem_wake() will be called whenever it
detects that some writers/readers are waiting. The rwsem_wake()
function will take the wait_lock and call __rwsem_do_wake() to do the
real wakeup. For a heavily contended rwsem, doing a spin_lock() on
wait_lock will cause further contention on the heavily contended rwsem
cacheline resulting in delay in the completion of the up_read/up_write
operations.
This patch makes the wait_lock taking and the call to __rwsem_do_wake()
optional if at least one spinning writer is present. The spinning
writer will be able to take the rwsem and call rwsem_wake() later
when it calls up_write(). With the presence of a spinning writer,
rwsem_wake() will now try to acquire the lock using trylock. If that
fails, it will just quit.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Jason Low <jason.low2@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430428337-16802-2-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Stephane asked about PERF_COUNT_SW_CPU_MIGRATIONS and I realized it
was borken:
> The problem is that the task isn't actually scheduled while its being
> migrated (obviously), and if its not scheduled, the counters aren't
> scheduled either, so there's no observing of the fact.
>
> A further problem with migrations is that many migrations happen from
> softirq context, which is nested inside the 'random' task context of
> whoemever happens to run at that time, similarly for the wakeup
> migrations triggered from (soft)irq context. All those end up being
> accounted in the task that's currently running, eg. your 'ls'.
The below cures this by marking a task as migrated and accounting it
on the subsequent sched_in().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Given the overall futex architecture, any chance of reducing
hb->lock contention is welcome. In this particular case, using
wake-queues to enable lockless wakeups addresses very much real
world performance concerns, even cases of soft-lockups in cases
of large amounts of blocked tasks (which is not hard to find in
large boxes, using but just a handful of futex).
At the lowest level, this patch can reduce latency of a single thread
attempting to acquire hb->lock in highly contended scenarios by a
up to 2x. At lower counts of nr_wake there are no regressions,
confirming, of course, that the wake_q handling overhead is practically
non existent. For instance, while a fair amount of variation,
the extended pef-bench wakeup benchmark shows for a 20 core machine
the following avg per-thread time to wakeup its share of tasks:
nr_thr ms-before ms-after
16 0.0590 0.0215
32 0.0396 0.0220
48 0.0417 0.0182
64 0.0536 0.0236
80 0.0414 0.0097
96 0.0672 0.0152
Naturally, this can cause spurious wakeups. However there is no core code
that cannot handle them afaict, and furthermore tglx does have the point
that other events can already trigger them anyway.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Mason <clm@fb.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: George Spelvin <linux@horizon.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1430494072-30283-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This is useful for locking primitives that can effect multiple
wakeups per operation and want to avoid lock internal lock contention
by delaying the wakeups until we've released the lock internal locks.
Alternatively it can be used to avoid issuing multiple wakeups, and
thus save a few cycles, in packet processing. Queue all target tasks
and wakeup once you've processed all packets. That way you avoid
waking the target task multiple times if there were multiple packets
for the same task.
Properties of a wake_q are:
- Lockless, as queue head must reside on the stack.
- Being a queue, maintains wakeup order passed by the callers. This can
be important for otherwise, in scenarios where highly contended locks
could affect any reliance on lock fairness.
- A queued task cannot be added again until it is woken up.
This patch adds the needed infrastructure into the scheduler code
and uses the new wake_list to delay the futex wakeups until
after we've released the hash bucket locks.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[tweaks, adjustments, comments, etc.]
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Mason <clm@fb.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: George Spelvin <linux@horizon.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1430494072-30283-2-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Recent optimizations were made to thread_group_cputimer to improve its
scalability by keeping track of cputime stats without a lock. However,
the values were open coded to the structure, causing them to be at
a different abstraction level from the regular task_cputime structure.
Furthermore, any subsequent similar optimizations would not be able to
share the new code, since they are specific to thread_group_cputimer.
This patch adds the new task_cputime_atomic data structure (introduced in
the previous patch in the series) to thread_group_cputimer for keeping
track of the cputime atomically, which also helps generalize the code.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1430251224-5764-6-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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improve scalability
While running a database workload, we found a scalability issue with itimers.
Much of the problem was caused by the thread_group_cputimer spinlock.
Each time we account for group system/user time, we need to obtain a
thread_group_cputimer's spinlock to update the timers. On larger systems
(such as a 16 socket machine), this caused more than 30% of total time
spent trying to obtain this kernel lock to update these group timer stats.
This patch converts the timers to 64-bit atomic variables and use
atomic add to update them without a lock. With this patch, the percent
of total time spent updating thread group cputimer timers was reduced
from 30% down to less than 1%.
Note: On 32-bit systems using the generic 64-bit atomics, this causes
sample_group_cputimer() to take locks 3 times instead of just 1 time.
However, we tested this patch on a 32-bit system ARM system using the
generic atomics and did not find the overhead to be much of an issue.
An explanation for why this isn't an issue is that 32-bit systems usually
have small numbers of CPUs, and cacheline contention from extra spinlocks
called periodically is not really apparent on smaller systems.
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1430251224-5764-4-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The p->mm->numa_scan_seq is accessed using READ_ONCE/WRITE_ONCE
and modified without exclusive access. It is not clear why it is
accessed this way. This patch provides some documentation on that.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Waiman Long <waiman.long@hp.com>
Link: http://lkml.kernel.org/r/1430440094.2475.61.camel@j-VirtualBox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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READ_ONCE()/WRITE_ONCE()
ACCESS_ONCE doesn't work reliably on non-scalar types. This patch removes
the rest of the existing usages of ACCESS_ONCE() in the scheduler, and use
the new READ_ONCE() and WRITE_ONCE() APIs as appropriate.
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Waiman Long <Waiman.Long@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1430251224-5764-2-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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'rt_period_us' is automatically type converted from u64 to long and then cast
back to u64 - this down/up conversion is unnecessary and can be removed to
improve readability.
This will also help us not truncate 'rt_period_us' to 32 bits on 32-bit kernels,
should we ever have so large values. (unlikely, not the least due to procfs.)
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430643116-24049-1-git-send-email-hofrat@osadl.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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c56fb6564dcd ("Fix a misaligned load inside ptrace_attach()") makes
jobctl an "unsigned long". It makes sense to have the masks applied
to it match that type. This is currently just a cosmetic change, but
it will prevent the mask from being unexpectedly truncated if we ever
end up with masks with more bits.
One instance of "signr" is an int, but I left this alone because the
mask ensures that it will never overflow.
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: oleg@redhat.com
Cc: paulmck@linux.vnet.ibm.com
Cc: richard@nod.at
Cc: vdavydov@parallels.com
Link: http://lkml.kernel.org/r/1430453997-32459-4-git-send-email-palmer@dabbelt.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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I could not find the loadavg code.. turns out it was hidden in a file
called proc.c. It further got mingled up with the cruft per rq load
indexes (which we really want to get rid of).
Move the per rq load indexes into the fair.c load-balance code (that's
the only thing that uses them) and rename proc.c to loadavg.c so we
can find it again.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
[ Did minor cleanups to the code. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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While fuzzing Sasha tripped over another ctx->mutex recursion lockdep
splat. Annotate this.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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We removed __cpuinit support (leaving no-op stubs) quite some time
ago. However this one crept back in as of commit a803f0261bb2bb57aab
("sched: Initialize rq->age_stamp on processor start")
Since we want to clobber the stubs too, get this removed now.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Corey Minyard <cminyard@mvista.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430174880-27958-2-git-send-email-paul.gortmaker@windriver.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Commit 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in
cpuset_cpu_inactive()"), a SCHED_DEADLINE bugfix, had a logic error that
caused a regression in setting a CPU inactive during suspend. I ran into
this when a program was failing pthread_setaffinity_np() with EINVAL after
a suspend+wake up.
A simple reproducer:
$ ./a.out
sched_setaffinity: Success
$ systemctl suspend
$ ./a.out
sched_setaffinity: Invalid argument
... where ./a.out is:
#define _GNU_SOURCE
#include <errno.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(void)
{
long num_cores;
cpu_set_t cpu_set;
int ret;
num_cores = sysconf(_SC_NPROCESSORS_ONLN);
CPU_ZERO(&cpu_set);
CPU_SET(num_cores - 1, &cpu_set);
errno = 0;
ret = sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set);
perror("sched_setaffinity");
return ret ? EXIT_FAILURE : EXIT_SUCCESS;
}
The mistake is that suspend is handled in the action ==
CPU_DOWN_PREPARE_FROZEN case of the switch statement in
cpuset_cpu_inactive().
However, the commit in question masked out CPU_TASKS_FROZEN
from the action, making this case dead.
The fix is straightforward.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()")
Link: http://lkml.kernel.org/r/1cb5ecb3d6543c38cce5790387f336f54ec8e2bc.1430733960.git.osandov@osandov.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Ronny reported that the following scenario is not handled correctly:
T1 (prio = 10)
lock(rtmutex);
T2 (prio = 20)
lock(rtmutex)
boost T1
T1 (prio = 20)
sys_set_scheduler(prio = 30)
T1 prio = 30
....
sys_set_scheduler(prio = 10)
T1 prio = 30
The last step is wrong as T1 should now be back at prio 20.
Commit c365c292d059 ("sched: Consider pi boosting in setscheduler()")
only handles the case where a boosted tasks tries to lower its
priority.
Fix it by taking the new effective priority into account for the
decision whether a change of the priority is required.
Reported-by: Ronny Meeus <ronny.meeus@gmail.com>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@vger.kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Fixes: c365c292d059 ("sched: Consider pi boosting in setscheduler()")
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1505051806060.4225@nanos
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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So this isn't really a fix but a cleanup that can wait for v4.2.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Simon Horman reported this crash on a system with
high-res timers disabled but nohz enabled:
> ------------[ cut here ]------------
> kernel BUG at kernel/irq_work.c:135!
BUG_ON(!irqs_disabled());
So something enabled interrupts in the periodic tick handling machinery,
and that code path indeed has a local_irq_disable()/enable pair in
tick_nohz_switch_to_nohz() which causes havoc. Fix it.
This patch also fixes a +nohz -hrtimers hang reported by Ingo Molnar.
Reported-by: Simon Horman <horms@verge.net.au>
Reported-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1505071425520.4225@nanos
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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nohz_full is only useful with isolcpus are also set, since
otherwise the scheduler has to run periodically to try to
determine whether to steal work from other cores.
Accordingly, when booting with nohz_full=xxx on the command
line, we should act as if isolcpus=xxx was also set, and set
(or extend) the isolcpus set to include the nohz_full cpus.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Jones <davej@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430928266-24888-5-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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TIF_NOHZ is used by context_tracking to force syscall slow-path
on every task in order to track userspace roundtrips. As such,
it must be set on all running tasks.
It's currently explicitly inherited through context switches.
There is no need to do it in this fast-path though. The flag
could simply be set once for all on all tasks, whether they are
running or not.
Lets do this by setting the flag for the init task on early boot,
and let it propagate through fork inheritance.
While at it, mark context_tracking_cpu_set() as init code, we
only need it at early boot time.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Dave Jones <davej@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430928266-24888-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Context tracking recursion can happen when an exception triggers
in the middle of a call to a context tracking probe.
This special case can be caused by vmalloc faults. If an access
to a memory area allocated by vmalloc happens in the middle of
context_tracking_enter(), we may run into an endless fault loop
because the exception in turn calls context_tracking_enter()
which faults on the same vmalloc'ed memory, triggering an
exception again, etc...
Some rare crashes have been reported so lets protect against
this with a recursion counter.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430928266-24888-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The only caller to this function (__print_array) was getting it wrong by
passing the array length instead of buffer length. As the element size
was already being passed for other reasons it seems reasonable to push
the calculation of buffer length into the function.
Link: http://lkml.kernel.org/r/1430320727-14582-1-git-send-email-alex.bennee@linaro.org
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU fix from Ingo Molnar:
"An RCU Kconfig fix that eliminates an annoying interactive kconfig
question for CONFIG_RCU_TORTURE_TEST_SLOW_INIT"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcu: Control grace-period delays directly from value
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unused
The hrtimer callback in the hrtimer's tick broadcast code sometimes
incorrectly ends up scheduling events at the current tick causing the
kernel to hang servicing the same hrtimer forever. This typically
happens when a device is swapped out by
tick_install_broadcast_device(), which replaces the event handler with
clock_events_handle_noop() and sets the device mode to
CLOCK_EVT_MODE_UNUSED. If the timer is scheduled when this happens,
the next_event field will not be updated and the hrtimer ends up being
restarted at the current tick. To prevent this from happening, only
try to restart the hrtimer if the broadcast clock event device is in
one of the active modes and try to cancel the timer when entering the
CLOCK_EVT_MODE_UNUSED mode.
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1429880765-5558-1-git-send-email-andreas.sandberg@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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The return type of kstat_irqs_usr() is unsigned int and kstat_irqs() also
returns unsigned int so sum should be unsigned int here as well.
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Link: http://lkml.kernel.org/r/1430642951-23964-1-git-send-email-hofrat@osadl.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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kstat_irqs is unsigned int and the return type of kstat_irqs() is also
unsigned int so sum should be unsigned int as well even if the result
is correct due to automatic type conversion.
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Link: http://lkml.kernel.org/r/1430642930-23929-1-git-send-email-hofrat@osadl.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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The irq_domain_ops are not modified. The irqdomain core code accepts
pointer to a const data.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Lee Jones <lee@kernel.org>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-rpi-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Link: http://lkml.kernel.org/r/1430139264-4362-1-git-send-email-k.kozlowski.k@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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At present, internal_add_timer() examines flags with 'base' which doesn't
contain flags. Examine with 'timer->base' to avoid unnecessary waking up
of nohz CPU when timer base has TIMER_DEFERRABLE set.
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Cc: sboyd@codeaurora.org
Cc: skannan@codeaurora.org
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1430187709-21087-1-git-send-email-joonwoop@codeaurora.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Today the number of bits of the broadcast masks that is output into
/proc/timer_list is sizeof(unsigned long). This means that on machines
with a larger number of CPUs, the bitmasks of CPUs beyond this range do
not appear.
Fix this by using bitmap printing through "%*pb" instead, so as to
output the broadcast masks for the range of nr_cpu_ids into
/proc/timer_list.
Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: peterz@infradead.org
Cc: linuxppc-dev@ozlabs.org
Cc: john.stultz@linaro.org
Link: http://lkml.kernel.org/r/20150428084520.3314.62668.stgit@preeti.in.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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|
Simplify the oneshot logic by avoiding the reprogramming loops. That
also allows to call the cpu local handler outside of the
broadcast_lock held region.
Tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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With the removal of the hrtimer softirq the switch to highres/nohz
mode happens in the tick interrupt. That leads to a livelock when the
per cpu event handler is directly called from the broadcast handler
under broadcast lock because broadcast lock needs to be taken for the
highres/nohz switch as well.
Solve this by calling the cpu local handler outside the broadcast_lock
held region.
Fixes: c6eb3f70d448 "hrtimer: Get rid of hrtimer softirq"
Reported-and-tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Since cpuidle_reflect() should only be called if the idle state
to enter was selected by cpuidle_select(), there is the "reflect"
variable in cpuidle_idle_call() whose value is used to determine
whether or not that is the case.
However, if the entire code run between the conditional setting
"reflect" and the call to cpuidle_reflect() is moved to a separate
function, it will be possible to call that new function in both
branches of the conditional, in which case cpuidle_reflect() will
only need to be called from one of them too and the "reflect"
variable won't be necessary any more.
This eliminates one check made by cpuidle_idle_call() on the majority
of its invocations, so change the code as described.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Move the code under the "use_default" label in cpuidle_idle_call()
into a separate (new) function.
This just allows the subsequent changes to be more stratightforward.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
|
|
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Pull networking fixes from David Miller:
1) Receive packet length needs to be adjust by 2 on RX to accomodate
the two padding bytes in altera_tse driver. From Vlastimil Setka.
2) If rx frame is dropped due to out of memory in macb driver, we leave
the receive ring descriptors in an undefined state. From Punnaiah
Choudary Kalluri
3) Some netlink subsystems erroneously signal NLM_F_MULTI. That is
only for dumps. Fix from Nicolas Dichtel.
4) Fix mis-use of raw rt->rt_pmtu value in ipv4, one must always go via
the ipv4_mtu() helper. From Herbert Xu.
5) Fix null deref in bridge netfilter, and miscalculated lengths in
jump/goto nf_tables verdicts. From Florian Westphal.
6) Unhash ping sockets properly.
7) Software implementation of BPF divide did 64/32 rather than 64/64
bit divide. The JITs got it right. Fix from Alexei Starovoitov.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (30 commits)
ipv4: Missing sk_nulls_node_init() in ping_unhash().
net: fec: Fix RGMII-ID mode
net/mlx4_en: Schedule napi when RX buffers allocation fails
netxen_nic: use spin_[un]lock_bh around tx_clean_lock
net/mlx4_core: Fix unaligned accesses
mlx4_en: Use correct loop cursor in error path.
cxgb4: Fix MC1 memory offset calculation
bnx2x: Delay during kdump load
net: Fix Kernel Panic in bonding driver debugfs file: rlb_hash_table
net: dsa: Fix scope of eeprom-length property
net: macb: Fix race condition in driver when Rx frame is dropped
hv_netvsc: Fix a bug in netvsc_start_xmit()
altera_tse: Correct rx packet length
mlx4: Fix tx ring affinity_mask creation
tipc: fix problem with parallel link synchronization mechanism
tipc: remove wrong use of NLM_F_MULTI
bridge/nl: remove wrong use of NLM_F_MULTI
bridge/mdb: remove wrong use of NLM_F_MULTI
net: sched: act_connmark: don't zap skb->nfct
trivial: net: systemport: bcmsysport.h: fix 0x0x prefix
...
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git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management and ACPI fixes from Rafael Wysocki:
"Three regression fixes this time, one for a recent regression in the
cpuidle core affecting multiple systems, one for an inadvertently
added duplicate typedef in ACPICA that breaks compilation with GCC 4.5
and one for an ACPI Smart Battery Subsystem driver regression
introduced during the 3.18 cycle (stable-candidate).
Specifics:
- Fix for a regression in the cpuidle core introduced by one of the
recent commits in the clockevents_notify() removal series that put
a call to a function which had to be executed with disabled
interrupts into a code path running with enabled interrupts (Rafael
J Wysocki)
- Fix for a build problem in ACPICA (with GCC 4.5) introduced by one
of the recent ACPICA tools commits that added a duplicate typedef
to one of the ACPICA's header files by mistake (Olaf Hering)
- Fix for a regression in the ACPI SBS (Smart Battery Subsystem)
driver introduced during the 3.18 development cycle causing the
smart battery manager to be marked as not present when it should be
marked as present (Chris Bainbridge)"
* tag 'pm+acpi-4.1-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpuidle: Run tick_broadcast_exit() with disabled interrupts
ACPI / SBS: Enable battery manager when present
ACPICA: remove duplicate u8 typedef
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Pull kvm changes from Paolo Bonzini:
"Remove from guest code the handling of task migration during a pvclock
read; instead use the correct protocol in KVM.
This removes the need for task migration notifiers in core scheduler
code"
[ The scheduler people really hated the migration notifiers, so this was
kind of required - Linus ]
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
x86: pvclock: Really remove the sched notifier for cross-cpu migrations
kvm: x86: fix kvmclock update protocol
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Change default key details to be more obviously unspecified.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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