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2020-09-16irqdomain/msi: Provide DOMAIN_BUS_VMD_MSIThomas Gleixner
PCI devices behind a VMD bus are not subject to interrupt remapping, but the irq domain for VMD MSI cannot be distinguished from a regular PCI/MSI irq domain. Add a new domain bus token and allow it in the bus token check in msi_check_reservation_mode() to keep the functionality the same once VMD uses this token. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Marc Zyngier <maz@kernel.org> Acked-by: Jon Derrick <jonathan.derrick@intel.com> Link: https://lore.kernel.org/r/20200826112332.954409970@linutronix.de
2020-09-16x86/msi: Use generic MSI domain opsThomas Gleixner
pci_msi_get_hwirq() and pci_msi_set_desc are not longer special. Enable the generic MSI domain ops in the core and PCI MSI code unconditionally and get rid of the x86 specific implementations in the X86 MSI code and in the hyperv PCI driver. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20200826112332.564274859@linutronix.de
2020-09-16genirq/chip: Use the first chip in irq_chip_compose_msi_msg()Thomas Gleixner
The documentation of irq_chip_compose_msi_msg() claims that with hierarchical irq domains the first chip in the hierarchy which has an irq_compose_msi_msg() callback is chosen. But the code just keeps iterating after it finds a chip with a compose callback. The x86 HPET MSI implementation relies on that behaviour, but that does not make it more correct. The message should always be composed at the domain which manages the underlying resource (e.g. APIC or remap table) because that domain knows about the required layout of the message. On X86 the following hierarchies exist: 1) vector -------- PCI/MSI 2) vector -- IR -- PCI/MSI The vector domain has a different message format than the IR (remapping) domain. So obviously the PCI/MSI domain can't compose the message without having knowledge about the parent domain, which is exactly the opposite of what hierarchical domains want to achieve. X86 actually has two different PCI/MSI chips where #1 has a compose callback and #2 does not. #2 delegates the composition to the remap domain where it belongs, but #1 does it at the PCI/MSI level. For the upcoming device MSI support it's necessary to change this and just let the first domain which can compose the message take care of it. That way the top level chip does not have to worry about it and the device MSI code does not need special knowledge about topologies. It just sets the compose callback to NULL and lets the hierarchy pick the first chip which has one. Due to that the attempt to move the compose callback from the direct delivery PCI/MSI domain to the vector domain made the system fail to boot with interrupt remapping enabled because in the remapping case irq_chip_compose_msi_msg() keeps iterating and choses the compose callback of the vector domain which obviously creates the wrong format for the remap table. Break out of the loop when the first irq chip with a compose callback is found and fixup the HPET code temporarily. That workaround will be removed once the direct delivery compose callback is moved to the place where it belongs in the vector domain. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20200826112331.047917603@linutronix.de
2020-09-16locking/percpu-rwsem: Use this_cpu_{inc,dec}() for read_countHou Tao
The __this_cpu*() accessors are (in general) IRQ-unsafe which, given that percpu-rwsem is a blocking primitive, should be just fine. However, file_end_write() is used from IRQ context and will cause load-store issues on architectures where the per-cpu accessors are not natively irq-safe. Fix it by using the IRQ-safe this_cpu_*() for operations on read_count. This will generate more expensive code on a number of platforms, which might cause a performance regression for some of the other percpu-rwsem users. If any such is reported, we can consider alternative solutions. Fixes: 70fe2f48152e ("aio: fix freeze protection of aio writes") Signed-off-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Link: https://lkml.kernel.org/r/20200915140750.137881-1-houtao1@huawei.com
2020-09-16softirq: Add debug check to __raise_softirq_irqoff()Jiafei Pan
__raise_softirq_irqoff() must be called with interrupts disabled to protect the per CPU softirq pending state update against an interrupt and soft interrupt handling on return from interrupt. Add a lockdep assertion to validate the calling convention. [ tglx: Massaged changelog ] Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20200814045522.45719-1-Jiafei.Pan@nxp.com
2020-09-15Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpfDavid S. Miller
Alexei Starovoitov says: ==================== pull-request: bpf 2020-09-15 The following pull-request contains BPF updates for your *net* tree. We've added 12 non-merge commits during the last 19 day(s) which contain a total of 10 files changed, 47 insertions(+), 38 deletions(-). The main changes are: 1) docs/bpf fixes, from Andrii. 2) ld_abs fix, from Daniel. 3) socket casting helpers fix, from Martin. 4) hash iterator fixes, from Yonghong. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-15bpf: Fix a rcu warning for bpffs map pretty-printYonghong Song
Running selftest ./btf_btf -p the kernel had the following warning: [ 51.528185] WARNING: CPU: 3 PID: 1756 at kernel/bpf/hashtab.c:717 htab_map_get_next_key+0x2eb/0x300 [ 51.529217] Modules linked in: [ 51.529583] CPU: 3 PID: 1756 Comm: test_btf Not tainted 5.9.0-rc1+ #878 [ 51.530346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.el7.centos 04/01/2014 [ 51.531410] RIP: 0010:htab_map_get_next_key+0x2eb/0x300 ... [ 51.542826] Call Trace: [ 51.543119] map_seq_next+0x53/0x80 [ 51.543528] seq_read+0x263/0x400 [ 51.543932] vfs_read+0xad/0x1c0 [ 51.544311] ksys_read+0x5f/0xe0 [ 51.544689] do_syscall_64+0x33/0x40 [ 51.545116] entry_SYSCALL_64_after_hwframe+0x44/0xa9 The related source code in kernel/bpf/hashtab.c: 709 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) 710 { 711 struct bpf_htab *htab = container_of(map, struct bpf_htab, map); 712 struct hlist_nulls_head *head; 713 struct htab_elem *l, *next_l; 714 u32 hash, key_size; 715 int i = 0; 716 717 WARN_ON_ONCE(!rcu_read_lock_held()); In kernel/bpf/inode.c, bpffs map pretty print calls map->ops->map_get_next_key() without holding a rcu_read_lock(), hence causing the above warning. To fix the issue, just surrounding map->ops->map_get_next_key() with rcu read lock. Fixes: a26ca7c982cb ("bpf: btf: Add pretty print support to the basic arraymap") Reported-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Cc: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20200916004401.146277-1-yhs@fb.com
2020-09-15printk: reimplement log_cont using record extensionJohn Ogness
Use the record extending feature of the ringbuffer to implement continuous messages. This preserves the existing continuous message behavior. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-7-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: add finalization/extension supportJohn Ogness
Add support for extending the newest data block. For this, introduce a new finalization state (desc_finalized) denoting a committed descriptor that cannot be extended. Until a record is finalized, a writer can reopen that record to append new data. Reopening a record means transitioning from the desc_committed state back to the desc_reserved state. A writer can explicitly finalize a record if there is no intention of extending it. Also, records are automatically finalized when a new record is reserved. This relieves writers of needing to explicitly finalize while also making such records available to readers sooner. (Readers can only traverse finalized records.) Four new memory barrier pairs are introduced. Two of them are insignificant additions (data_realloc:A/desc_read:D and data_realloc:A/data_push_tail:B) because they are alternate path memory barriers that exactly match the purpose, pairing, and context of the two existing memory barrier pairs they provide an alternate path for. The other two new memory barrier pairs are significant additions: desc_reopen_last:A / _prb_commit:B - When reopening a descriptor, ensure the state transitions back to desc_reserved before fully trusting the descriptor data. _prb_commit:B / desc_reserve:D - When committing a descriptor, ensure the state transitions to desc_committed before checking the head ID to see if the descriptor needs to be finalized. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-6-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: change representation of statesJohn Ogness
Rather than deriving the state by evaluating bits within the flags area of the state variable, assign the states explicit values and set those values in the flags area. Introduce macros to make it simple to read and write state values for the state variable. Although the functionality is preserved, the binary representation for the states is changed. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-5-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: clear initial reserved fieldsJohn Ogness
prb_reserve() will set some meta data values and leave others uninitialized (or rather, containing the values of the previous wrap). Simplify the API by always clearing out all the fields. Only the sequence number is filled in. The caller is now responsible for filling in the rest of the meta data fields. In particular, for correctly filling in text and dict lengths. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-4-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: add BLK_DATALESS() macroJohn Ogness
Rather than continually needing to explicitly check @begin and @next to identify a dataless block, introduce and use a BLK_DATALESS() macro. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-3-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: relocate get_data()John Ogness
Move the internal get_data() function as-is above prb_reserve() so that a later change can make use of the static function. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-2-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: avoid memcpy() on state_varJohn Ogness
@state_var is copied as part of the descriptor copying via memcpy(). This is not allowed because @state_var is an atomic type, which in some implementations may contain a spinlock. Avoid using memcpy() with @state_var by explicitly copying the other fields of the descriptor. @state_var is set using atomic set operator before returning. Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914094803.27365-2-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: fix setting state in desc_read()John Ogness
It is expected that desc_read() will always set at least the @state_var field. However, if the descriptor is in an inconsistent state, no fields are set. Also, the second load of @state_var is not stored in @desc_out and so might not match the state value that is returned. Always set the last loaded @state_var into @desc_out, regardless of the descriptor consistency. Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914094803.27365-1-john.ogness@linutronix.de
2020-09-14core/entry: Report syscall correctly for trace and auditKees Cook
On v5.8 when doing seccomp syscall rewrites (e.g. getpid into getppid as seen in the seccomp selftests), trace (and audit) correctly see the rewritten syscall on entry and exit: seccomp_bpf-1307 [000] .... 22974.874393: sys_enter: NR 110 (... seccomp_bpf-1307 [000] .N.. 22974.874401: sys_exit: NR 110 = 1304 With mainline we see a mismatched enter and exit (the original syscall is incorrectly visible on entry): seccomp_bpf-1030 [000] .... 21.806766: sys_enter: NR 39 (... seccomp_bpf-1030 [000] .... 21.806767: sys_exit: NR 110 = 1027 When ptrace or seccomp change the syscall, this needs to be visible to trace and audit at that time as well. Update the syscall earlier so they see the correct value. Fixes: d88d59b64ca3 ("core/entry: Respect syscall number rewrites") Reported-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20200912005826.586171-1-keescook@chromium.org
2020-09-14kprobes: Fix to check probe enabled before disarm_kprobe_ftrace()Masami Hiramatsu
Commit: 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler") fixed one bug but the underlying bugs are not completely fixed yet. If we run a kprobe_module.tc of ftracetest, a warning triggers: # ./ftracetest test.d/kprobe/kprobe_module.tc === Ftrace unit tests === [1] Kprobe dynamic event - probing module ... ------------[ cut here ]------------ Failed to disarm kprobe-ftrace at trace_printk_irq_work+0x0/0x7e [trace_printk] (-2) WARNING: CPU: 7 PID: 200 at kernel/kprobes.c:1091 __disarm_kprobe_ftrace.isra.0+0x7e/0xa0 This is because the kill_kprobe() calls disarm_kprobe_ftrace() even if the given probe is not enabled. In that case, ftrace_set_filter_ip() fails because the given probe point is not registered to ftrace. Fix to check the given (going) probe is enabled before invoking disarm_kprobe_ftrace(). Fixes: 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler") Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/159888672694.1411785.5987998076694782591.stgit@devnote2
2020-09-14lockdep: fix order in trace_hardirqs_off_caller()Sven Schnelle
Switch order so that locking state is consistent even if the IRQ tracer calls into lockdep again. Acked-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2020-09-13genirq: Allow interrupts to be excluded from /proc/interruptsMarc Zyngier
A number of architectures implement IPI statistics directly, duplicating the core kstat_irqs accounting. As we move IPIs to being actual IRQs, we would end-up with a confusing display in /proc/interrupts (where the IPIs would appear twice). In order to solve this, allow interrupts to be flagged as "hidden", which excludes them from /proc/interrupts. Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
2020-09-13genirq: Add fasteoi IPI flowMarc Zyngier
For irqchips using the fasteoi flow, IPIs are a bit special. They need to be EOI'd early (before calling the handler), as funny things may happen in the handler (they do not necessarily behave like a normal interrupt). Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
2020-09-12Merge tag 'seccomp-v5.9-rc5' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull seccomp fixes from Kees Cook: "This fixes a rare race condition in seccomp when using TSYNC and USER_NOTIF together where a memory allocation would not get freed (found by syzkaller, fixed by Tycho). Additionally updates Tycho's MAINTAINERS and .mailmap entries for his new address" * tag 'seccomp-v5.9-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: seccomp: don't leave dangling ->notif if file allocation fails mailmap, MAINTAINERS: move to tycho.pizza seccomp: don't leak memory when filter install races
2020-09-11gcov: add support for GCC 10.1Peter Oberparleiter
Using gcov to collect coverage data for kernels compiled with GCC 10.1 causes random malfunctions and kernel crashes. This is the result of a changed GCOV_COUNTERS value in GCC 10.1 that causes a mismatch between the layout of the gcov_info structure created by GCC profiling code and the related structure used by the kernel. Fix this by updating the in-kernel GCOV_COUNTERS value. Also re-enable config GCOV_KERNEL for use with GCC 10. Reported-by: Colin Ian King <colin.king@canonical.com> Reported-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com> Tested-by: Leon Romanovsky <leonro@nvidia.com> Tested-and-Acked-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-09-10perf/core: Pull pmu::sched_task() into perf_event_context_sched_out()Kan Liang
The pmu::sched_task() is a context switch callback. It passes the cpuctx->task_ctx as a parameter to the lower code. To find the cpuctx->task_ctx, the current code iterates a cpuctx list. The same context will iterated in perf_event_context_sched_out() soon. Share the cpuctx->task_ctx can avoid the unnecessary iteration of the cpuctx list. The pmu::sched_task() is also required for the optimization case for equivalent contexts. The task_ctx_sched_out() will eventually disable and reenable the PMU when schedule out events. Add perf_pmu_disable() and perf_pmu_enable() around task_ctx_sched_out() don't break anything. Drop the cpuctx->ctx.lock for the pmu::sched_task(). The lock is for per-CPU context, which is not necessary for the per-task context schedule. No one uses sched_cb_entry, perf_sched_cb_usages, sched_cb_list, and perf_pmu_sched_task() any more. Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200821195754.20159-2-kan.liang@linux.intel.com
2020-09-10perf/core: Pull pmu::sched_task() into perf_event_context_sched_in()Kan Liang
The pmu::sched_task() is a context switch callback. It passes the cpuctx->task_ctx as a parameter to the lower code. To find the cpuctx->task_ctx, the current code iterates a cpuctx list. The same context was just iterated in perf_event_context_sched_in(), which is invoked right before the pmu::sched_task(). Reuse the cpuctx->task_ctx from perf_event_context_sched_in() can avoid the unnecessary iteration of the cpuctx list. Both pmu::sched_task and perf_event_context_sched_in() have to disable PMU. Pull the pmu::sched_task into perf_event_context_sched_in() can also save the overhead from the PMU disable and reenable. The new and old tasks may have equivalent contexts. The current code optimize this case by swapping the context, which avoids the scheduling. For this case, pmu::sched_task() is still required, e.g., restore the LBR content. Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200821195754.20159-1-kan.liang@linux.intel.com
2020-09-10timekeeping: Use seqcount_latch_tAhmed S. Darwish
Latch sequence counters are a multiversion concurrency control mechanism where the seqcount_t counter even/odd value is used to switch between two data storage copies. This allows the seqcount_t read path to safely interrupt its write side critical section (e.g. from NMIs). Initially, latch sequence counters were implemented as a single write function, raw_write_seqcount_latch(), above plain seqcount_t. The read path was expected to use plain seqcount_t raw_read_seqcount(). A specialized read function was later added, raw_read_seqcount_latch(), and became the standardized way for latch read paths. Having unique read and write APIs meant that latch sequence counters are basically a data type of their own -- just inappropriately overloading plain seqcount_t. The seqcount_latch_t data type was thus introduced at seqlock.h. Use that new data type instead of seqcount_raw_spinlock_t. This ensures that only latch-safe APIs are to be used with the sequence counter. Note that the use of seqcount_raw_spinlock_t was not very useful in the first place. Only the "raw_" subset of seqcount_t APIs were used at timekeeping.c. This subset was created for contexts where lockdep cannot be used. seqcount_LOCKTYPE_t's raison d'être -- verifying that the seqcount_t writer serialization lock is held -- cannot thus be done. References: 0c3351d451ae ("seqlock: Use raw_ prefix instead of _no_lockdep") References: 55f3560df975 ("seqlock: Extend seqcount API with associated locks") Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200827114044.11173-6-a.darwish@linutronix.de
2020-09-10time/sched_clock: Use seqcount_latch_tAhmed S. Darwish
Latch sequence counters have unique read and write APIs, and thus seqcount_latch_t was recently introduced at seqlock.h. Use that new data type instead of plain seqcount_t. This adds the necessary type-safety and ensures only latching-safe seqcount APIs are to be used. Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200827114044.11173-5-a.darwish@linutronix.de
2020-09-10time/sched_clock: Use raw_read_seqcount_latch() during suspendAhmed S. Darwish
sched_clock uses seqcount_t latching to switch between two storage places protected by the sequence counter. This allows it to have interruptible, NMI-safe, seqcount_t write side critical sections. Since 7fc26327b756 ("seqlock: Introduce raw_read_seqcount_latch()"), raw_read_seqcount_latch() became the standardized way for seqcount_t latch read paths. Due to the dependent load, it has one read memory barrier less than the currently used raw_read_seqcount() API. Use raw_read_seqcount_latch() for the suspend path. Commit aadd6e5caaac ("time/sched_clock: Use raw_read_seqcount_latch()") missed changing that instance of raw_read_seqcount(). References: 1809bfa44e10 ("timers, sched/clock: Avoid deadlock during read from NMI") Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
2020-09-09Merge branch 'linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 Pull crypto fix from Herbert Xu: "This fixes a regression in padata" * 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: padata: fix possible padata_works_lock deadlock
2020-09-09sched/topology: Move sd_flag_debug out of #ifdef CONFIG_SYSCTLValentin Schneider
The last sd_flag_debug shuffle inadvertently moved its definition within an #ifdef CONFIG_SYSCTL region. While CONFIG_SYSCTL is indeed required to produce the sched domain ctl interface (which uses sd_flag_debug to output flag names), it isn't required to run any assertion on the sched_domain hierarchy itself. Move the definition of sd_flag_debug to a CONFIG_SCHED_DEBUG region of topology.c. Now at long last we have: - sd_flag_debug declared in include/linux/sched/topology.h iff CONFIG_SCHED_DEBUG=y - sd_flag_debug defined in kernel/sched/topology.c, conditioned by: - CONFIG_SCHED_DEBUG, with an explicit #ifdef block - CONFIG_SMP, as a requirement to compile topology.c With this change, all symbols pertaining to SD flag metadata (with the exception of __SD_FLAG_CNT) are now defined exclusively within topology.c Fixes: 8fca9494d4b4 ("sched/topology: Move sd_flag_debug out of linux/sched/topology.h") Reported-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200908184956.23369-1-valentin.schneider@arm.com
2020-09-08seccomp: don't leave dangling ->notif if file allocation failsTycho Andersen
Christian and Kees both pointed out that this is a bit sloppy to open-code both places, and Christian points out that we leave a dangling pointer to ->notif if file allocation fails. Since we check ->notif for null in order to determine if it's ok to install a filter, this means people won't be able to install a filter if the file allocation fails for some reason, even if they subsequently should be able to. To fix this, let's hoist this free+null into its own little helper and use it. Reported-by: Kees Cook <keescook@chromium.org> Reported-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Tycho Andersen <tycho@tycho.pizza> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20200902140953.1201956-1-tycho@tycho.pizza Signed-off-by: Kees Cook <keescook@chromium.org>
2020-09-08seccomp: don't leak memory when filter install racesTycho Andersen
In seccomp_set_mode_filter() with TSYNC | NEW_LISTENER, we first initialize the listener fd, then check to see if we can actually use it later in seccomp_may_assign_mode(), which can fail if anyone else in our thread group has installed a filter and caused some divergence. If we can't, we partially clean up the newly allocated file: we put the fd, put the file, but don't actually clean up the *memory* that was allocated at filter->notif. Let's clean that up too. To accomplish this, let's hoist the actual "detach a notifier from a filter" code to its own helper out of seccomp_notify_release(), so that in case anyone adds stuff to init_listener(), they only have to add the cleanup code in one spot. This does a bit of extra locking and such on the failure path when the filter is not attached, but it's a slow failure path anyway. Fixes: 51891498f2da ("seccomp: allow TSYNC and USER_NOTIF together") Reported-by: syzbot+3ad9614a12f80994c32e@syzkaller.appspotmail.com Signed-off-by: Tycho Andersen <tycho@tycho.pizza> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20200902014017.934315-1-tycho@tycho.pizza Signed-off-by: Kees Cook <keescook@chromium.org>
2020-09-08kprobes: Make local functions staticMasami Hiramatsu
Since we unified the kretprobe trampoline handler from arch/* code, some functions and objects do not need to be exported anymore. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/159870618256.1229682.8692046612635810882.stgit@devnote2
2020-09-08kprobes: Free kretprobe_instance with RCU callbackMasami Hiramatsu
Free kretprobe_instance with RCU callback instead of directly freeing the object in the kretprobe handler context. This will make kretprobe run safer in NMI context. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/159870616685.1229682.11978742048709542226.stgit@devnote2
2020-09-08kprobes: Remove NMI context checkMasami Hiramatsu
The in_nmi() check in pre_handler_kretprobe() is meant to avoid recursion, and blindly assumes that anything NMI is recursive. However, since commit: 9b38cc704e84 ("kretprobe: Prevent triggering kretprobe from within kprobe_flush_task") there is a better way to detect and avoid actual recursion. By setting a dummy kprobe, any actual exceptions will terminate early (by trying to handle the dummy kprobe), and recursion will not happen. Employ this to avoid the kretprobe_table_lock() recursion, replacing the over-eager in_nmi() check. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/159870615628.1229682.6087311596892125907.stgit@devnote2
2020-09-08kprobes: Add generic kretprobe trampoline handlerMasami Hiramatsu
Add a generic kretprobe trampoline handler for unifying the all cloned /arch/* kretprobe trampoline handlers. The generic kretprobe trampoline handler is based on the x86 implementation, because it is the latest implementation. It has frame pointer checking, kprobe_busy_begin/end and return address fixup for user handlers. [ mingo: Minor edits. ] Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/159870600138.1229682.3424065380448088833.stgit@devnote2
2020-09-08printk: ringbuffer: support dataless recordsJohn Ogness
With commit 896fbe20b4e2333fb55 ("printk: use the lockless ringbuffer"), printk() started silently dropping messages without text because such records are not supported by the new printk ringbuffer. Add support for such records. Currently dataless records are denoted by INVALID_LPOS in order to recognize failed prb_reserve() calls. Change the ringbuffer to instead use two different identifiers (FAILED_LPOS and NO_LPOS) to distinguish between failed prb_reserve() records and successful dataless records, respectively. Fixes: 896fbe20b4e2333fb55 ("printk: use the lockless ringbuffer") Fixes: https://lkml.kernel.org/r/20200718121053.GA691245@elver.google.com Reported-by: Marco Elver <elver@google.com> Signed-off-by: John Ogness <john.ogness@linutronix.de> Cc: Petr Mladek <pmladek@suse.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Marco Elver <elver@google.com> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200721132528.9661-1-john.ogness@linutronix.de
2020-09-07blktrace: make function blk_trace_bio_get_cgid() staticWang Hai
The sparse tool complains as follows: kernel/trace/blktrace.c:796:5: warning: symbol 'blk_trace_bio_get_cgid' was not declared. Should it be static? This function is not used outside of blktrace.c, so this commit marks it static. Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Wang Hai <wanghai38@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-09-06Merge tag 'x86-urgent-2020-09-06' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 fixes from Ingo Molnar: - more generic entry code ABI fallout - debug register handling bugfixes - fix vmalloc mappings on 32-bit kernels - kprobes instrumentation output fix on 32-bit kernels - fix over-eager WARN_ON_ONCE() on !SMAP hardware - NUMA debugging fix - fix Clang related crash on !RETPOLINE kernels * tag 'x86-urgent-2020-09-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/entry: Unbreak 32bit fast syscall x86/debug: Allow a single level of #DB recursion x86/entry: Fix AC assertion tracing/kprobes, x86/ptrace: Fix regs argument order for i386 x86, fakenuma: Fix invalid starting node ID x86/mm/32: Bring back vmalloc faulting on x86_32 x86/cmdline: Disable jump tables for cmdline.c
2020-09-06genirq: Walk the irq_data hierarchy when resending an interruptMarc Zyngier
On resending an interrupt, we only check the outermost irqchip for a irq_retrigger callback. However, this callback could be implemented at an inner level. Use irq_chip_retrigger_hierarchy() in this case. Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
2020-09-05Merge branch 'akpm' (patches from Andrew)Linus Torvalds
Merge misc fixes from Andrew Morton: "19 patches. Subsystems affected by this patch series: MAINTAINERS, ipc, fork, checkpatch, lib, and mm (memcg, slub, pagemap, madvise, migration, hugetlb)" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: include/linux/log2.h: add missing () around n in roundup_pow_of_two() mm/khugepaged.c: fix khugepaged's request size in collapse_file mm/hugetlb: fix a race between hugetlb sysctl handlers mm/hugetlb: try preferred node first when alloc gigantic page from cma mm/migrate: preserve soft dirty in remove_migration_pte() mm/migrate: remove unnecessary is_zone_device_page() check mm/rmap: fixup copying of soft dirty and uffd ptes mm/migrate: fixup setting UFFD_WP flag mm: madvise: fix vma user-after-free checkpatch: fix the usage of capture group ( ... ) fork: adjust sysctl_max_threads definition to match prototype ipc: adjust proc_ipc_sem_dointvec definition to match prototype mm: track page table modifications in __apply_to_page_range() MAINTAINERS: IA64: mark Status as Odd Fixes only MAINTAINERS: add LLVM maintainers MAINTAINERS: update Cavium/Marvell entries mm: slub: fix conversion of freelist_corrupted() mm: memcg: fix memcg reclaim soft lockup memcg: fix use-after-free in uncharge_batch
2020-09-05fork: adjust sysctl_max_threads definition to match prototypeTobias Klauser
Commit 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler") changed ctl_table.proc_handler to take a kernel pointer. Adjust the definition of sysctl_max_threads to match its prototype in linux/sysctl.h which fixes the following sparse error/warning: kernel/fork.c:3050:47: warning: incorrect type in argument 3 (different address spaces) kernel/fork.c:3050:47: expected void * kernel/fork.c:3050:47: got void [noderef] __user *buffer kernel/fork.c:3036:5: error: symbol 'sysctl_max_threads' redeclared with different type (incompatible argument 3 (different address spaces)): kernel/fork.c:3036:5: int extern [addressable] [signed] [toplevel] sysctl_max_threads( ... ) kernel/fork.c: note: in included file (through include/linux/key.h, include/linux/cred.h, include/linux/sched/signal.h, include/linux/sched/cputime.h): include/linux/sysctl.h:242:5: note: previously declared as: include/linux/sysctl.h:242:5: int extern [addressable] [signed] [toplevel] sysctl_max_threads( ... ) Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler") Signed-off-by: Tobias Klauser <tklauser@distanz.ch> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Link: https://lkml.kernel.org/r/20200825093647.24263-1-tklauser@distanz.ch Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-09-04gcov: Disable gcov build with GCC 10Leon Romanovsky
GCOV built with GCC 10 doesn't initialize n_function variable. This produces different kernel panics as was seen by Colin in Ubuntu and me in FC 32. As a workaround, let's disable GCOV build for broken GCC 10 version. Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1891288 Link: https://lore.kernel.org/lkml/20200827133932.3338519-1-leon@kernel.org Link: https://lore.kernel.org/lkml/CAHk-=whbijeSdSvx-Xcr0DPMj0BiwhJ+uiNnDSVZcr_h_kg7UA@mail.gmail.com/ Cc: Colin Ian King <colin.king@canonical.com> Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-09-04x86/entry: Unbreak 32bit fast syscallThomas Gleixner
Andy reported that the syscall treacing for 32bit fast syscall fails: # ./tools/testing/selftests/x86/ptrace_syscall_32 ... [RUN] SYSEMU [FAIL] Initial args are wrong (nr=224, args=10 11 12 13 14 4289172732) ... [RUN] SYSCALL [FAIL] Initial args are wrong (nr=29, args=0 0 0 0 0 4289172732) The eason is that the conversion to generic entry code moved the retrieval of the sixth argument (EBP) after the point where the syscall entry work runs, i.e. ptrace, seccomp, audit... Unbreak it by providing a split up version of syscall_enter_from_user_mode(). - syscall_enter_from_user_mode_prepare() establishes state and enables interrupts - syscall_enter_from_user_mode_work() runs the entry work Replace the call to syscall_enter_from_user_mode() in the 32bit fast syscall C-entry with the split functions and stick the EBP retrieval between them. Fixes: 27d6b4d14f5c ("x86/entry: Use generic syscall entry function") Reported-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/87k0xdjbtt.fsf@nanos.tec.linutronix.de
2020-09-04padata: fix possible padata_works_lock deadlockDaniel Jordan
syzbot reports, WARNING: inconsistent lock state 5.9.0-rc2-syzkaller #0 Not tainted -------------------------------- inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage. syz-executor.0/26715 takes: (padata_works_lock){+.?.}-{2:2}, at: padata_do_parallel kernel/padata.c:220 {IN-SOFTIRQ-W} state was registered at: spin_lock include/linux/spinlock.h:354 [inline] padata_do_parallel kernel/padata.c:220 ... __do_softirq kernel/softirq.c:298 ... sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt arch/x86/include/asm/idtentry.h:581 Possible unsafe locking scenario: CPU0 ---- lock(padata_works_lock); <Interrupt> lock(padata_works_lock); padata_do_parallel() takes padata_works_lock with softirqs enabled, so a deadlock is possible if, on the same CPU, the lock is acquired in process context and then softirq handling done in an interrupt leads to the same path. Fix by leaving softirqs disabled while do_parallel holds padata_works_lock. Reported-by: syzbot+f4b9f49e38e25eb4ef52@syzkaller.appspotmail.com Fixes: 4611ce2246889 ("padata: allocate work structures for parallel jobs from a pool") Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: linux-crypto@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2020-09-03Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netLinus Torvalds
Pull networking fixes from David Miller: 1) Use netif_rx_ni() when necessary in batman-adv stack, from Jussi Kivilinna. 2) Fix loss of RTT samples in rxrpc, from David Howells. 3) Memory leak in hns_nic_dev_probe(), from Dignhao Liu. 4) ravb module cannot be unloaded, fix from Yuusuke Ashizuka. 5) We disable BH for too lokng in sctp_get_port_local(), add a cond_resched() here as well, from Xin Long. 6) Fix memory leak in st95hf_in_send_cmd, from Dinghao Liu. 7) Out of bound access in bpf_raw_tp_link_fill_link_info(), from Yonghong Song. 8) Missing of_node_put() in mt7530 DSA driver, from Sumera Priyadarsini. 9) Fix crash in bnxt_fw_reset_task(), from Michael Chan. 10) Fix geneve tunnel checksumming bug in hns3, from Yi Li. 11) Memory leak in rxkad_verify_response, from Dinghao Liu. 12) In tipc, don't use smp_processor_id() in preemptible context. From Tuong Lien. 13) Fix signedness issue in mlx4 memory allocation, from Shung-Hsi Yu. 14) Missing clk_disable_prepare() in gemini driver, from Dan Carpenter. 15) Fix ABI mismatch between driver and firmware in nfp, from Louis Peens. * git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (110 commits) net/smc: fix sock refcounting in case of termination net/smc: reset sndbuf_desc if freed net/smc: set rx_off for SMCR explicitly net/smc: fix toleration of fake add_link messages tg3: Fix soft lockup when tg3_reset_task() fails. doc: net: dsa: Fix typo in config code sample net: dp83867: Fix WoL SecureOn password nfp: flower: fix ABI mismatch between driver and firmware tipc: fix shutdown() of connectionless socket ipv6: Fix sysctl max for fib_multipath_hash_policy drivers/net/wan/hdlc: Change the default of hard_header_len to 0 net: gemini: Fix another missing clk_disable_unprepare() in probe net: bcmgenet: fix mask check in bcmgenet_validate_flow() amd-xgbe: Add support for new port mode net: usb: dm9601: Add USB ID of Keenetic Plus DSL vhost: fix typo in error message net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init() pktgen: fix error message with wrong function name net: ethernet: ti: am65-cpsw: fix rmii 100Mbit link mode cxgb4: fix thermal zone device registration ...
2020-09-03bpf: Do not use bucket_lock for hashmap iteratorYonghong Song
Currently, for hashmap, the bpf iterator will grab a bucket lock, a spinlock, before traversing the elements in the bucket. This can ensure all bpf visted elements are valid. But this mechanism may cause deadlock if update/deletion happens to the same bucket of the visited map in the program. For example, if we added bpf_map_update_elem() call to the same visited element in selftests bpf_iter_bpf_hash_map.c, we will have the following deadlock: ============================================ WARNING: possible recursive locking detected 5.9.0-rc1+ #841 Not tainted -------------------------------------------- test_progs/1750 is trying to acquire lock: ffff9a5bb73c5e70 (&htab->buckets[i].raw_lock){....}-{2:2}, at: htab_map_update_elem+0x1cf/0x410 but task is already holding lock: ffff9a5bb73c5e20 (&htab->buckets[i].raw_lock){....}-{2:2}, at: bpf_hash_map_seq_find_next+0x94/0x120 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&htab->buckets[i].raw_lock); lock(&htab->buckets[i].raw_lock); *** DEADLOCK *** ... Call Trace: dump_stack+0x78/0xa0 __lock_acquire.cold.74+0x209/0x2e3 lock_acquire+0xba/0x380 ? htab_map_update_elem+0x1cf/0x410 ? __lock_acquire+0x639/0x20c0 _raw_spin_lock_irqsave+0x3b/0x80 ? htab_map_update_elem+0x1cf/0x410 htab_map_update_elem+0x1cf/0x410 ? lock_acquire+0xba/0x380 bpf_prog_ad6dab10433b135d_dump_bpf_hash_map+0x88/0xa9c ? find_held_lock+0x34/0xa0 bpf_iter_run_prog+0x81/0x16e __bpf_hash_map_seq_show+0x145/0x180 bpf_seq_read+0xff/0x3d0 vfs_read+0xad/0x1c0 ksys_read+0x5f/0xe0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ... The bucket_lock first grabbed in seq_ops->next() called by bpf_seq_read(), and then grabbed again in htab_map_update_elem() in the bpf program, causing deadlocks. Actually, we do not need bucket_lock here, we can just use rcu_read_lock() similar to netlink iterator where the rcu_read_{lock,unlock} likes below: seq_ops->start(): rcu_read_lock(); seq_ops->next(): rcu_read_unlock(); /* next element */ rcu_read_lock(); seq_ops->stop(); rcu_read_unlock(); Compared to old bucket_lock mechanism, if concurrent updata/delete happens, we may visit stale elements, miss some elements, or repeat some elements. I think this is a reasonable compromise. For users wanting to avoid stale, missing/repeated accesses, bpf_map batch access syscall interface can be used. Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200902235340.2001375-1-yhs@fb.com
2020-09-03locking/lockdep: Fix "USED" <- "IN-NMI" inversionspeterz@infradead.org
During the LPC RCU BoF Paul asked how come the "USED" <- "IN-NMI" detector doesn't trip over rcu_read_lock()'s lockdep annotation. Looking into this I found a very embarrasing typo in verify_lock_unused(): - if (!(class->usage_mask & LOCK_USED)) + if (!(class->usage_mask & LOCKF_USED)) fixing that will indeed cause rcu_read_lock() to insta-splat :/ The above typo means that instead of testing for: 0x100 (1 << LOCK_USED), we test for 8 (LOCK_USED), which corresponds to (1 << LOCK_ENABLED_HARDIRQ). So instead of testing for _any_ used lock, it will only match any lock used with interrupts enabled. The rcu_read_lock() annotation uses .check=0, which means it will not set any of the interrupt bits and will thus never match. In order to properly fix the situation and allow rcu_read_lock() to correctly work, split LOCK_USED into LOCK_USED and LOCK_USED_READ and by having .read users set USED_READ and test USED, pure read-recursive locks are permitted. Fixes: f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20200902160323.GK1362448@hirez.programming.kicks-ass.net
2020-09-01tracepoint: Optimize using static_call()Steven Rostedt (VMware)
Currently the tracepoint site will iterate a vector and issue indirect calls to however many handlers are registered (ie. the vector is long). Using static_call() it is possible to optimize this for the common case of only having a single handler registered. In this case the static_call() can directly call this handler. Otherwise, if the vector is longer than 1, call a function that iterates the whole vector like the current code. [peterz: updated to new interface] Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20200818135805.279421092@infradead.org
2020-09-01static_call: Allow early initPeter Zijlstra
In order to use static_call() to wire up x86_pmu, we need to initialize earlier, specifically before memory allocation works; copy some of the tricks from jump_label to enable this. Primarily we overload key->next to store a sites pointer when there are no modules, this avoids having to use kmalloc() to initialize the sites and allows us to run much earlier. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20200818135805.220737930@infradead.org
2020-09-01static_call: Handle tail-callsPeter Zijlstra
GCC can turn our static_call(name)(args...) into a tail call, in which case we get a JMP.d32 into the trampoline (which then does a further tail-call). Teach objtool to recognise and mark these in .static_call_sites and adjust the code patching to deal with this. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20200818135805.101186767@infradead.org