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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into perf/urgent
Pull tracing fixes from Steven Rostedt.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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With the recent locking updates, the only thing protected by
workqueue_lock is workqueue->maydays list. Rename workqueue_lock to
wq_mayday_lock.
This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
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This patch continues locking cleanup from the previous patch. It
breaks out pool_workqueue synchronization from workqueue_lock into a
new spinlock - pwq_lock. The followings are protected by pwq_lock.
* workqueue->pwqs
* workqueue->saved_max_active
The conversion is straight-forward. workqueue_lock usages which cover
the above two are converted to pwq_lock. New locking label PW added
for things protected by pwq_lock and FR is updated to mean flush_mutex
+ pwq_lock + sched-RCU.
This patch shouldn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently, workqueue_lock protects most shared workqueue resources -
the pools, workqueues, pool_workqueues, draining, ID assignments,
mayday handling and so on. The coverage has grown organically and
there is no identified bottleneck coming from workqueue_lock, but it
has grown a bit too much and scheduled rebinding changes need the
pools and workqueues to be protected by a mutex instead of a spinlock.
This patch breaks out pool and workqueue synchronization from
workqueue_lock into a new mutex - wq_mutex. The followings are
protected by wq_mutex.
* worker_pool_idr and unbound_pool_hash
* pool->refcnt
* workqueues list
* workqueue->flags, ->nr_drainers
Most changes are mostly straight-forward. workqueue_lock is replaced
with wq_mutex where applicable and workqueue_lock lock/unlocks are
added where wq_mutex conversion leaves data structures not protected
by wq_mutex without locking. irq / preemption flippings were added
where the conversion affects them. Things worth noting are
* New WQ and WR locking lables added along with
assert_rcu_or_wq_mutex().
* worker_pool_assign_id() now expects to be called under wq_mutex.
* create_mutex is removed from get_unbound_pool(). It now just holds
wq_mutex.
This patch shouldn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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They're split across debugobj code for some reason. Collect them.
This patch is pure relocation.
Signed-off-by: Tejun Heo <tj@kernel.org>
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When a manager creates or destroys workers, the operations are always
done with the manager_mutex held; however, initial worker creation or
worker destruction during pool release don't grab the mutex. They are
still correct as initial worker creation doesn't require
synchronization and grabbing manager_arb provides enough exclusion for
pool release path.
Still, let's make everyone follow the same rules for consistency and
such that lockdep annotations can be added.
Update create_and_start_worker() and put_unbound_pool() to grab
manager_mutex around thread creation and destruction respectively and
add lockdep assertions to create_worker() and destroy_worker().
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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get_unbound_pool(), workqueue_cpu_up_callback() and init_workqueues()
have similar code pieces to create and start the initial worker factor
those out into create_and_start_worker().
This patch doesn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Manager operations are currently governed by two mutexes -
pool->manager_arb and ->assoc_mutex. The former is used to decide who
gets to be the manager and the latter to exclude the actual manager
operations including creation and destruction of workers. Anyone who
grabs ->manager_arb must perform manager role; otherwise, the pool
might stall.
Grabbing ->assoc_mutex blocks everyone else from performing manager
operations but doesn't require the holder to perform manager duties as
it's merely blocking manager operations without becoming the manager.
Because the blocking was necessary when [dis]associating per-cpu
workqueues during CPU hotplug events, the latter was named
assoc_mutex. The mutex is scheduled to be used for other purposes, so
this patch gives it a more fitting generic name - manager_mutex - and
updates / adds comments to explain synchronization around the manager
role and operations.
This patch is pure rename / doc update.
Signed-off-by: Tejun Heo <tj@kernel.org>
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There's no reason to make these trivial wrappers full (exported)
functions. Inline the followings.
queue_work()
queue_delayed_work()
mod_delayed_work()
schedule_work_on()
schedule_work()
schedule_delayed_work_on()
schedule_delayed_work()
keventd_up()
Signed-off-by: Tejun Heo <tj@kernel.org>
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Rename @id argument of for_each_pool() to @pi so that it doesn't get
reused accidentally when for_each_pool() is used in combination with
other iterators.
This patch is purely cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org>
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* Update incorrect and add missing synchronization labels.
* Update incorrect or misleading comments. Add new comments where
clarification is necessary. Reformat / rephrase some comments.
* drain_workqueue() can be used separately from destroy_workqueue()
but its warning message was incorrectly referring to destruction.
Other than the warning message change, this patch doesn't make any
functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Since 9e8cd2f589 ("workqueue: implement apply_workqueue_attrs()"),
init_and_link_pwq() may be called to initialize a new pool_workqueue
for a workqueue which is already online, but the function was setting
pwq->max_active to wq->saved_max_active without proper
synchronization.
Fix it by calling pwq_adjust_max_active() under proper locking instead
of manually setting max_active.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Rename pwq_set_max_active() to pwq_adjust_max_active() and move
pool_workqueue->max_active synchronization and max_active
determination logic into it.
The new function should be called with workqueue_lock held for stable
workqueue->saved_max_active, determines the current max_active value
the target pool_workqueue should be using from @wq->saved_max_active
and the state of the associated pool, and applies it with proper
synchronization.
The current two users - workqueue_set_max_active() and
thaw_workqueues() - are updated accordingly. In addition, the manual
freezing handling in __alloc_workqueue_key() and
freeze_workqueues_begin() are replaced with calls to
pwq_adjust_max_active().
This centralizes max_active handling so that it's less error-prone.
Signed-off-by: Tejun Heo <tj@kernel.org>
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pwq_set_max_active() is gonna be modified and used during
pool_workqueue init. Move it above init_and_link_pwq().
This patch is pure code reorganization and doesn't introduce any
functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Merge misc fixes from Andrew Morton:
- A bunch of fixes
- Finish off the idr API conversions before someone starts to use the
old interfaces again.
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
idr: idr_alloc() shouldn't trigger lowmem warning when preloaded
UAPI: fix endianness conditionals in M32R's asm/stat.h
UAPI: fix endianness conditionals in linux/raid/md_p.h
UAPI: fix endianness conditionals in linux/acct.h
UAPI: fix endianness conditionals in linux/aio_abi.h
decompressors: fix typo "POWERPC"
mm/fremap.c: fix oops on error path
idr: deprecate idr_pre_get() and idr_get_new[_above]()
tidspbridge: convert to idr_alloc()
zcache: convert to idr_alloc()
mlx4: remove leftover idr_pre_get() call
workqueue: convert to idr_alloc()
nfsd: convert to idr_alloc()
nfsd: remove unused get_new_stid()
kernel/signal.c: use __ARCH_HAS_SA_RESTORER instead of SA_RESTORER
signal: always clear sa_restorer on execve
mm: remove_memory(): fix end_pfn setting
include/linux/res_counter.h needs errno.h
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idr_get_new*() and friends are about to be deprecated. Convert to the
new idr_alloc() interface.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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__ARCH_HAS_SA_RESTORER is the preferred conditional for use in 3.9 and
later kernels, per Kees.
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When the new signal handlers are set up, the location of sa_restorer is
not cleared, leaking a parent process's address space location to
children. This allows for a potential bypass of the parent's ASLR by
examining the sa_restorer value returned when calling sigaction().
Based on what should be considered "secret" about addresses, it only
matters across the exec not the fork (since the VMAs haven't changed
until the exec). But since exec sets SIG_DFL and keeps sa_restorer,
this is where it should be fixed.
Given the few uses of sa_restorer, a "set" function was not written
since this would be the only use. Instead, we use
__ARCH_HAS_SA_RESTORER, as already done in other places.
Example of the leak before applying this patch:
$ cat /proc/$$/maps
...
7fb9f3083000-7fb9f3238000 r-xp 00000000 fd:01 404469 .../libc-2.15.so
...
$ ./leak
...
7f278bc74000-7f278be29000 r-xp 00000000 fd:01 404469 .../libc-2.15.so
...
1 0 (nil) 0x7fb9f30b94a0
2 4000000 (nil) 0x7f278bcaa4a0
3 4000000 (nil) 0x7f278bcaa4a0
4 0 (nil) 0x7fb9f30b94a0
...
[akpm@linux-foundation.org: use SA_RESTORER for backportability]
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Emese Revfy <re.emese@gmail.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Julien Tinnes <jln@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Don't allowing sharing the root directory with processes in a
different user namespace. There doesn't seem to be any point, and to
allow it would require the overhead of putting a user namespace
reference in fs_struct (for permission checks) and incrementing that
reference count on practically every call to fork.
So just perform the inexpensive test of forbidding sharing fs_struct
acrosss processes in different user namespaces. We already disallow
other forms of threading when unsharing a user namespace so this
should be no real burden in practice.
This updates setns, clone, and unshare to disallow multiple user
namespaces sharing an fs_struct.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Because function tracing is very invasive, and can even trace
calls to rcu_read_lock(), RCU access in function tracing is done
with preempt_disable_notrace(). This requires a synchronize_sched()
for updates and not a synchronize_rcu().
Function probes (traceon, traceoff, etc) must be freed after
a synchronize_sched() after its entry has been removed from the
hash. But call_rcu() is used. Fix this by using call_rcu_sched().
Also fix the usage to use hlist_del_rcu() instead of hlist_del().
Cc: stable@vger.kernel.org
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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In some situations, randomly delaying RCU grace-period initialization
can cause more trouble than help. This commit therefore restricts this
type of RCU self-torture to runtime, giving it a rest during boot and
shutdown.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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If RCU's softirq handler is prevented from executing, an RCU CPU stall
warning can result. Ways to prevent RCU's softirq handler from executing
include: (1) CPU spinning with interrupts disabled, (2) infinite loop
in some softirq handler, and (3) in -rt kernels, an infinite loop in a
set of real-time threads running at priorities higher than that of RCU's
softirq handler.
Because this situation can be difficult to track down, this commit causes
the count of RCU softirq handler invocations to be printed with RCU
CPU stall warnings. This information does require some interpretation,
as now documented in Documentation/RCU/stallwarn.txt.
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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Some users have reported that after running a process with
hundreds of threads on intensive CPU-bound loads, the cputime
of the group started to freeze after a few days.
This is due to how we scale the tick-based cputime against
the scheduler precise execution time value.
We add the values of all threads in the group and we multiply
that against the sum of the scheduler exec runtime of the whole
group.
This easily overflows after a few days/weeks of execution.
A proposed solution to solve this was to compute that multiplication
on stime instead of utime:
62188451f0d63add7ad0cd2a1ae269d600c1663d
("cputime: Avoid multiplication overflow on utime scaling")
The rationale behind that was that it's easy for a thread to
spend most of its time in userspace under intensive CPU-bound workload
but it's much harder to do CPU-bound intensive long run in the kernel.
This postulate got defeated when a user recently reported he was still
seeing cputime freezes after the above patch. The workload that
triggers this issue relates to intensive networking workloads where
most of the cputime is consumed in the kernel.
To reduce much more the opportunities for multiplication overflow,
lets reduce the multiplication factors to the remainders of the division
between sched exec runtime and cputime. Assuming the difference between
these shouldn't ever be that large, it could work on many situations.
This gets the same results as in the upstream scaling code except for
a small difference: the upstream code always rounds the results to
the nearest integer not greater to what would be the precise result.
The new code rounds to the nearest integer either greater or not
greater. In practice this difference probably shouldn't matter but
it's worth mentioning.
If this solution appears not to be enough in the end, we'll
need to partly revert back to the behaviour prior to commit
0cf55e1ec08bb5a22e068309e2d8ba1180ab4239
("sched, cputime: Introduce thread_group_times()")
Back then, the scaling was done on exit() time before adding the cputime
of an exiting thread to the signal struct. And then we'll need to
scale one-by-one the live threads cputime in thread_group_cputime(). The
drawback may be a slightly slower code on exit time.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
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On the CPU which gets woken along with the target CPU of the broadcast
the following happens:
deep_idle()
<-- spurious wakeup
broadcast_exit()
set forced bit
enable interrupts
<-- Nothing happens
disable interrupts
broadcast_enter()
<-- Here we observe the forced bit is set
deep_idle()
Now after that the target CPU of the broadcast runs the broadcast
handler and finds the other CPU in both the broadcast and the forced
mask, sends the IPI and stuff gets back to normal.
So it's not actually harmful, just more evidence for the theory, that
hardware designers have access to very special drug supplies.
Now there is no point in going back to deep idle just to wake up again
right away via an IPI. Provide a check which allows the idle code to
avoid the deep idle transition.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Jason Liu <liu.h.jason@gmail.com>
Link: http://lkml.kernel.org/r/20130306111537.565418308@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Some brilliant hardware implementations wake multiple cores when the
broadcast timer fires. This leads to the following interesting
problem:
CPU0 CPU1
wakeup from idle wakeup from idle
leave broadcast mode leave broadcast mode
restart per cpu timer restart per cpu timer
go back to idle
handle broadcast
(empty mask)
enter broadcast mode
programm broadcast device
enter broadcast mode
programm broadcast device
So what happens is that due to the forced reprogramming of the cpu
local timer, we need to set a event in the future. Now if we manage to
go back to idle before the timer fires, we switch off the timer and
arm the broadcast device with an already expired time (covered by
forced mode). So in the worst case we repeat the above ping pong
forever.
Unfortunately we have no information about what caused the wakeup, but
we can check current time against the expiry time of the local cpu. If
the local event is already in the past, we know that the broadcast
timer is about to fire and send an IPI. So we mark ourself as an IPI
target even if we left broadcast mode and avoid the reprogramming of
the local cpu timer.
This still leaves the possibility that a CPU which is not handling the
broadcast interrupt is going to reach idle again before the IPI
arrives. This can't be solved in the core code and will be handled in
follow up patches.
Reported-by: Jason Liu <liu.h.jason@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Link: http://lkml.kernel.org/r/20130306111537.492045206@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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If the local cpu timer stops in deep idle, we arm the broadcast device
and get woken by an IPI. Now when we return from deep idle we reenable
the local cpu timer unconditionally before handling the IPI. But
that's a pointless exercise: the timer is already expired and the IPI
is on the way. And it's an expensive exercise as we use the forced
reprogramming mode so that we do not lose a timer event. This forced
reprogramming will loop at least once in the retry.
To avoid this reprogramming, we mark the cpu in a pending bit mask
before we send the IPI. Now when the IPI target cpu wakes up, it will
see the pending bit set and skip the reprogramming. The reprogramming
of the cpu local timer will happen in the IPI handler which runs the
cpu local timer interrupt function.
Reported-by: Jason Liu <liu.h.jason@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Link: http://lkml.kernel.org/r/20130306111537.431082074@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Fold in upstream fixes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Fix kernel-doc warning in futex.c and convert 'Returns' to the new Return:
kernel-doc notation format.
Warning(kernel/futex.c:2286): Excess function parameter 'clockrt' description in 'futex_wait_requeue_pi'
Fix one spello.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Fix new kernel-doc warnings in kernel/signal.c:
Warning(kernel/signal.c:2689): No description found for parameter 'uset'
Warning(kernel/signal.c:2689): Excess function parameter 'set' description in 'sys_rt_sigpending'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Implement a function which queries whether it currently is running off
a workqueue rescuer. This will be used to convert writeback to
workqueue.
Signed-off-by: Tejun Heo <tj@kernel.org>
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eventfd_poll() never returns POLLHUP.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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When we open cgroup.procs, we'll allocate an buffer and store all tasks'
tgid in it, and then duplicate entries will be stripped. If that results
in a much smaller pid list, we'll re-allocate a smaller buffer.
But we've already sucessfully allocated memory and reading the procs
file is a short period and the memory will be freed very soon, so why
bother to re-allocate memory.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset no longer nests cgroup_mutex inside cpu_hotplug lock, so
we don't have to release cgroup_mutex before calling css_offline().
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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It was used by ns cgroup, and ns cgroup was removed long ago.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Sasha reported a lockdep warning when OOM was triggered. The reason
is cgroup_name() should be called with rcu_read_lock() held.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Although it used to be that CPU_DYING notifiers executed on the outgoing
CPU with interrupts disabled and with all other CPUs spinning, this is
no longer the case. This commit therefore removes this obsolete comment.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Offline CPUs transition through the scheduler to the idle loop one
last time before being shut down. This can result in RCU raising
softirq on this CPU, which is at best useless given that the CPU's
callbacks will be offloaded at CPU_DEAD time. This commit therefore
avoids raising softirq on offline CPUs.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Signed-off-by: Jiang Fang <jiang.xx.fang@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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A function type is typically defined as
typedef ret_type (*func)(args..)
but async_func_ptr is not. Redefine it.
Also rename async_func_ptr to async_func_t for _func_t suffix is more generic.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
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The code in lowest_in_progress() are duplicated in two branches,
simplify them.
tj: Minor indentation adjustment.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
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There are cases where workqueue users want to expose control knobs to
userland. e.g. Unbound workqueues with custom attributes are
scheduled to be used for writeback workers and depending on
configuration it can be useful to allow admins to tinker with the
priority or allowed CPUs.
This patch implements workqueue_sysfs_register(), which makes the
workqueue visible under /sys/bus/workqueue/devices/WQ_NAME. There
currently are two attributes common to both per-cpu and unbound pools
and extra attributes for unbound pools including nice level and
cpumask.
If alloc_workqueue*() is called with WQ_SYSFS,
workqueue_sysfs_register() is called automatically as part of
workqueue creation. This is the preferred method unless the workqueue
user wants to apply workqueue_attrs before making the workqueue
visible to userland.
v2: Disallow exposing ordered workqueues as ordered workqueues can't
be tuned in any way.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Adjusting max_active of or applying new workqueue_attrs to an ordered
workqueue breaks its ordering guarantee. The former is obvious. The
latter is because applying attrs creates a new pwq (pool_workqueue)
and there is no ordering constraint between the old and new pwqs.
Make apply_workqueue_attrs() and workqueue_set_max_active() trigger
WARN_ON() if those operations are requested on an ordered workqueue
and fail / ignore respectively.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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We're gonna add another internal WQ flag. Let's make the distinction
clear. Prefix WQ_DRAINING with __ and move it to bit 16.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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Implement apply_workqueue_attrs() which applies workqueue_attrs to the
specified unbound workqueue by creating a new pwq (pool_workqueue)
linked to worker_pool with the specified attributes.
A new pwq is linked at the head of wq->pwqs instead of tail and
__queue_work() verifies that the first unbound pwq has positive refcnt
before choosing it for the actual queueing. This is to cover the case
where creation of a new pwq races with queueing. As base ref on a pwq
won't be dropped without making another pwq the first one,
__queue_work() is guaranteed to make progress and not add work item to
a dead pwq.
init_and_link_pwq() is updated to return the last first pwq the new
pwq replaced, which is put by apply_workqueue_attrs().
Note that apply_workqueue_attrs() is almost identical to unbound pwq
part of alloc_and_link_pwqs(). The only difference is that there is
no previous first pwq. apply_workqueue_attrs() is implemented to
handle such cases and replaces unbound pwq handling in
alloc_and_link_pwqs().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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Because per-cpu workqueues have multiple pwqs (pool_workqueues) to
serve the CPUs, to guarantee that a single work item isn't queued on
one pwq while still executing another, __queue_work() takes a look at
the previous pool the target work item was on and if it's still
executing there, queue the work item on that pool.
To support changing workqueue_attrs on the fly, unbound workqueues too
will have multiple pwqs and thus need non-reentrancy test when
queueing. This patch modifies __queue_work() such that the reentrancy
test is performed regardless of the workqueue type.
per_cpu_ptr(wq->cpu_pwqs, cpu) used to be used to determine the
matching pwq for the last pool. This can't be used for unbound
workqueues and is replaced with worker->current_pwq which also happens
to be simpler.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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unbound pool_workqueues
Unbound pwqs (pool_workqueues) will be dynamically created and
destroyed with the scheduled unbound workqueue w/ custom attributes
support. This patch synchronizes pwq linking and unlinking against
flush_workqueue() so that its operation isn't disturbed by pwqs coming
and going.
Linking and unlinking a pwq into wq->pwqs is now protected also by
wq->flush_mutex and a new pwq's work_color is initialized to
wq->work_color during linking. This ensures that pwqs changes don't
disturb flush_workqueue() in progress and the new pwq's work coloring
stays in sync with the rest of the workqueue.
flush_mutex during unlinking isn't strictly necessary but it's simpler
to do it anyway.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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Add pool_workqueue->refcnt along with get/put_pwq(). Both per-cpu and
unbound pwqs have refcnts and any work item inserted on a pwq
increments the refcnt which is dropped when the work item finishes.
For per-cpu pwqs the base ref is never dropped and destroy_workqueue()
frees the pwqs as before. For unbound ones, destroy_workqueue()
simply drops the base ref on the first pwq. When the refcnt reaches
zero, pwq_unbound_release_workfn() is scheduled on system_wq, which
unlinks the pwq, puts the associated pool and frees the pwq and wq as
necessary. This needs to be done from a work item as put_pwq() needs
to be protected by pool->lock but release can't happen with the lock
held - e.g. put_unbound_pool() involves blocking operations.
Unbound pool->locks are marked with lockdep subclas 1 as put_pwq()
will schedule the release work item on system_wq while holding the
unbound pool's lock and triggers recursive locking warning spuriously.
This will be used to implement dynamic creation and destruction of
unbound pwqs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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* Move initialization and linking of pool_workqueues into
init_and_link_pwq().
* Make the failure path use destroy_workqueue() once pool_workqueue
initialization succeeds.
These changes are to prepare for dynamic management of pool_workqueues
and don't introduce any functional changes.
While at it, convert list_del(&wq->list) to list_del_init() as a
precaution as scheduled changes will make destruction more complex.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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