Commit Graph

49 Commits

Author SHA1 Message Date
Zqiang 25934fcfb9 irq_work: use kasan_record_aux_stack_noalloc() record callstack
On PREEMPT_RT kernel and KASAN is enabled.  the kasan_record_aux_stack()
may call alloc_pages(), and the rt-spinlock will be acquired, if currently
in atomic context, will trigger warning:

  BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
  in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 239, name: bootlogd
  Preemption disabled at:
  [<ffffffffbab1a531>] rt_mutex_slowunlock+0xa1/0x4e0
  CPU: 3 PID: 239 Comm: bootlogd Tainted: G        W 5.17.1-rt17-yocto-preempt-rt+ #105
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
  Call Trace:
     __might_resched.cold+0x13b/0x173
     rt_spin_lock+0x5b/0xf0
     get_page_from_freelist+0x20c/0x1610
     __alloc_pages+0x25e/0x5e0
     __stack_depot_save+0x3c0/0x4a0
     kasan_save_stack+0x3a/0x50
     __kasan_record_aux_stack+0xb6/0xc0
     kasan_record_aux_stack+0xe/0x10
     irq_work_queue_on+0x6a/0x1c0
     pull_rt_task+0x631/0x6b0
     do_balance_callbacks+0x56/0x80
     __balance_callbacks+0x63/0x90
     rt_mutex_setprio+0x349/0x880
     rt_mutex_slowunlock+0x22a/0x4e0
     rt_spin_unlock+0x49/0x80
     uart_write+0x186/0x2b0
     do_output_char+0x2e9/0x3a0
     n_tty_write+0x306/0x800
     file_tty_write.isra.0+0x2af/0x450
     tty_write+0x22/0x30
     new_sync_write+0x27c/0x3a0
     vfs_write+0x3f7/0x5d0
     ksys_write+0xd9/0x180
     __x64_sys_write+0x43/0x50
     do_syscall_64+0x44/0x90
     entry_SYSCALL_64_after_hwframe+0x44/0xae

Fix it by using kasan_record_aux_stack_noalloc() to avoid the call to
alloc_pages().

Link: https://lkml.kernel.org/r/20220402142555.2699582-1-qiang1.zhang@intel.com
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-04-15 14:49:55 -07:00
Sebastian Andrzej Siewior 09089db798 irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RT
On PREEMPT_RT most items are processed as LAZY via softirq context.
Avoid to spin-wait for them because irq_work_sync() could have higher
priority and not allow the irq-work to be completed.

Wait additionally for !IRQ_WORK_HARD_IRQ irq_work items on PREEMPT_RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-5-bigeasy@linutronix.de
2021-10-15 11:25:18 +02:00
Sebastian Andrzej Siewior b4c6f86ec2 irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RT
The irq_work callback is invoked in hard IRQ context. By default all
callbacks are scheduled for invocation right away (given supported by
the architecture) except for the ones marked IRQ_WORK_LAZY which are
delayed until the next timer-tick.

While looking over the callbacks, some of them may acquire locks
(spinlock_t, rwlock_t) which are transformed into sleeping locks on
PREEMPT_RT and must not be acquired in hard IRQ context.
Changing the locks into locks which could be acquired in this context
will lead to other problems such as increased latencies if everything
in the chain has IRQ-off locks. This will not solve all the issues as
one callback has been noticed which invoked kref_put() and its callback
invokes kfree() and this can not be invoked in hardirq context.

Some callbacks are required to be invoked in hardirq context even on
PREEMPT_RT to work properly. This includes for instance the NO_HZ
callback which needs to be able to observe the idle context.

The callbacks which require to be run in hardirq have already been
marked. Use this information to split the callbacks onto the two lists
on PREEMPT_RT:
- lazy_list
  Work items which are not marked with IRQ_WORK_HARD_IRQ will be added
  to this list. Callbacks on this list will be invoked from a per-CPU
  thread.
  The handler here may acquire sleeping locks such as spinlock_t and
  invoke kfree().

- raised_list
  Work items which are marked with IRQ_WORK_HARD_IRQ will be added to
  this list. They will be invoked in hardirq context and must not
  acquire any sleeping locks.

The wake up of the per-CPU thread occurs from irq_work handler/
hardirq context. The thread runs with lowest RT priority to ensure it
runs before any SCHED_OTHER tasks do.

[bigeasy: melt tglx's irq_work_tick_soft() which splits irq_work_tick() into a
	  hard and soft variant. Collected fixes over time from Steven
	  Rostedt and Mike Galbraith. Move to per-CPU threads instead of
	  softirq as suggested by PeterZ.]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211007092646.uhshe3ut2wkrcfzv@linutronix.de
2021-10-15 11:25:17 +02:00
Sebastian Andrzej Siewior 810979682c irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.
irq_work() triggers instantly an interrupt if supported by the
architecture. Otherwise the work will be processed on the next timer
tick. In worst case irq_work_sync() could spin up to a jiffy.

irq_work_sync() is usually used in tear down context which is fully
preemptible. Based on review irq_work_sync() is invoked from preemptible
context and there is one waiter at a time. This qualifies it to use
rcuwait for synchronisation.

Let irq_work_sync() synchronize with rcuwait if the architecture
processes irqwork via the timer tick.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-3-bigeasy@linutronix.de
2021-10-15 11:25:17 +02:00
Peter Zijlstra 156172a13f irq_work: Make irq_work_queue() NMI-safe again
Someone carelessly put NMI unsafe code in irq_work_queue(), breaking
just about every single user. Also, someone has a terrible comment
style.

Fixes: e2b5bcf9f5 ("irq_work: record irq_work_queue() call stack")
Reported-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YL+uBq8LzXXZsYVf@hirez.programming.kicks-ass.net
2021-06-10 10:00:08 +02:00
Zqiang e2b5bcf9f5 irq_work: record irq_work_queue() call stack
Add the irq_work_queue() call stack into the KASAN auxiliary stack in
order to improve KASAN reports.  this will let us know where the irq work
be queued.

Link: https://lkml.kernel.org/r/20210331063202.28770-1-qiang.zhang@windriver.com
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-30 11:20:42 -07:00
Peter Zijlstra 2914b0ba61 irq_work: Optimize irq_work_single()
Trade one atomic op for a full memory barrier.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
2020-11-24 16:47:49 +01:00
Peter Zijlstra 7a9f50a058 irq_work: Cleanup
Get rid of the __call_single_node union and clean up the API a little
to avoid external code relying on the structure layout as much.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
2020-11-24 16:47:48 +01:00
Peter Zijlstra 4b44a21dd6 irq_work, smp: Allow irq_work on call_single_queue
Currently irq_work_queue_on() will issue an unconditional
arch_send_call_function_single_ipi() and has the handler do
irq_work_run().

This is unfortunate in that it makes the IPI handler look at a second
cacheline and it misses the opportunity to avoid the IPI. Instead note
that struct irq_work and struct __call_single_data are very similar in
layout, so use a few bits in the flags word to encode a type and stick
the irq_work on the call_single_queue list.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200526161908.011635912@infradead.org
2020-05-28 10:54:15 +02:00
Sebastian Andrzej Siewior 49915ac35c lockdep: Annotate irq_work
Mark irq_work items with IRQ_WORK_HARD_IRQ which should be invoked in
hardirq context even on PREEMPT_RT. IRQ_WORK without this flag will be
invoked in softirq context on PREEMPT_RT.

Set ->irq_config to 1 for the IRQ_WORK items which are invoked in softirq
context so lockdep knows that these can safely acquire a spinlock_t.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.643576700@linutronix.de
2020-03-21 16:00:24 +01:00
Frederic Weisbecker e9838bd511 irq_work: Fix IRQ_WORK_BUSY bit clearing
While attempting to clear the busy bit at the end of a work execution,
atomic_cmpxchg() expects the value of the flags with the pending bit
cleared as the old value. However by mistake the value of the flags is
passed without clearing the pending bit first.

As a result, clearing the busy bit fails and irq_work_sync() may stall:

 watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [blktrace:4948]
 CPU: 0 PID: 4948 Comm: blktrace Not tainted 5.4.0-rc7-00003-gfeb4a51323bab #1
 RIP: 0010:irq_work_sync+0x4/0x10
 Call Trace:
  relay_close_buf+0x19/0x50
  relay_close+0x64/0x100
  blk_trace_free+0x1f/0x50
  __blk_trace_remove+0x1e/0x30
  blk_trace_ioctl+0x11b/0x140
  blkdev_ioctl+0x6c1/0xa40
  block_ioctl+0x39/0x40
  do_vfs_ioctl+0xa5/0x700
  ksys_ioctl+0x70/0x80
  __x64_sys_ioctl+0x16/0x20
  do_syscall_64+0x5b/0x1d0
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

So clear the appropriate bit before passing the old flags to cmpxchg().

Fixes: feb4a51323 ("irq_work: Slightly simplify IRQ_WORK_PENDING clearing")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Reported-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Leonard Crestez <leonard.crestez@nxp.com>
Link: https://lkml.kernel.org/r/20191113171201.14032-1-frederic@kernel.org
2019-11-15 10:48:37 +01:00
Frederic Weisbecker feb4a51323 irq_work: Slightly simplify IRQ_WORK_PENDING clearing
Instead of fetching the value of flags and perform an xchg() to clear
a bit, just use atomic_fetch_andnot() that is more suitable to do that
job in one operation while keeping the full ordering.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191108160858.31665-4-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-11-11 09:03:31 +01:00
Frederic Weisbecker 25269871db irq_work: Fix irq_work_claim() memory ordering
When irq_work_claim() finds IRQ_WORK_PENDING flag already set, we just
return and don't raise a new IPI. We expect the destination to see
and handle our latest updades thanks to the pairing atomic_xchg()
in irq_work_run_list().

But cmpxchg() doesn't guarantee a full memory barrier upon failure. So
it's possible that the destination misses our latest updates.

So use atomic_fetch_or() instead that is unconditionally fully ordered
and also performs exactly what we want here and simplify the code.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191108160858.31665-3-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-11-11 09:03:31 +01:00
Frederic Weisbecker 153bedbac2 irq_work: Convert flags to atomic_t
We need to convert flags to atomic_t in order to later fix an ordering
issue on atomic_cmpxchg() failure. This will allow us to use atomic_fetch_or().

Also clarify the nature of those flags.

[ mingo: Converted two more usage site the original patch missed. ]

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191108160858.31665-2-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-11-11 09:02:56 +01:00
Thomas Gleixner 457c899653 treewide: Add SPDX license identifier for missed files
Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-21 10:50:45 +02:00
Nicholas Piggin 471ba0e686 irq_work: Do not raise an IPI when queueing work on the local CPU
The QEMU PowerPC/PSeries machine model was not expecting a self-IPI,
and it may be a bit surprising thing to do, so have irq_work_queue_on
do local queueing when target is the current CPU.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@kaod.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190409093403.20994-1-npiggin@gmail.com
[ Simplified the preprocessor comments.
  Fixed unbalanced curly brackets pointed out by Thomas. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-04-18 14:07:52 +02:00
Bartosz Golaszewski 6baf9e67c9 irq/work: Improve the flag definitions
IRQ_WORK_FLAGS is defined simply to 3UL. This is confusing as it
says nothing about its purpose. Define IRQ_WORK_FLAGS as a bitwise
OR of IRQ_WORK_PENDING and IRQ_WORK_BUSY and change its name to
IRQ_WORK_CLAIMED.

While we're at it: use the BIT() macro for all flags.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1515125996-21564-1-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-01-08 19:43:15 +01:00
Linus Torvalds 670310dfba Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq core updates from Thomas Gleixner:
 "A rather large update for the interrupt core code and the irq chip drivers:

   - Add a new bitmap matrix allocator and supporting changes, which is
     used to replace the x86 vector allocator which comes with separate
     pull request. This allows to replace the convoluted nested loop
     allocation function in x86 with a facility which supports the
     recently added property of managed interrupts proper and allows to
     switch to a best effort vector reservation scheme, which addresses
     problems with vector exhaustion.

   - A large update to the ARM GIC-V3-ITS driver adding support for
     range selectors.

   - New interrupt controllers:
       - Meson and Meson8 GPIO
       - BCM7271 L2
       - Socionext EXIU

     If you expected that this will stop at some point, I have to
     disappoint you. There are new ones posted already. Sigh!

   - STM32 interrupt controller support for new platforms.

   - A pile of fixes, cleanups and updates to the MIPS GIC driver

   - The usual small fixes, cleanups and updates all over the place.
     Most visible one is to move the irq chip drivers Kconfig switches
     into a separate Kconfig menu"

* 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  genirq: Fix type of shifting literal 1 in __setup_irq()
  irqdomain: Drop pointless NULL check in virq_debug_show_one
  genirq/proc: Return proper error code when irq_set_affinity() fails
  irq/work: Use llist_for_each_entry_safe
  irqchip: mips-gic: Print warning if inherited GIC base is used
  irqchip/mips-gic: Add pr_fmt and reword pr_* messages
  irqchip/stm32: Move the wakeup on interrupt mask
  irqchip/stm32: Fix initial values
  irqchip/stm32: Add stm32h7 support
  dt-bindings/interrupt-controllers: Add compatible string for stm32h7
  irqchip/stm32: Add multi-bank management
  irqchip/stm32: Select GENERIC_IRQ_CHIP
  irqchip/exiu: Add support for Socionext Synquacer EXIU controller
  dt-bindings: Add description of Socionext EXIU interrupt controller
  irqchip/gic-v3-its: Fix VPE activate callback return value
  irqchip: mips-gic: Make IPI bitmaps static
  irqchip: mips-gic: Share register writes in gic_set_type()
  irqchip: mips-gic: Remove gic_vpes variable
  irqchip: mips-gic: Use num_possible_cpus() to reserve IPIs
  irqchip: mips-gic: Configure EIC when CPUs come online
  ...
2017-11-13 17:33:11 -08:00
Linus Torvalds 8e9a2dba86 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core locking updates from Ingo Molnar:
 "The main changes in this cycle are:

   - Another attempt at enabling cross-release lockdep dependency
     tracking (automatically part of CONFIG_PROVE_LOCKING=y), this time
     with better performance and fewer false positives. (Byungchul Park)

   - Introduce lockdep_assert_irqs_enabled()/disabled() and convert
     open-coded equivalents to lockdep variants. (Frederic Weisbecker)

   - Add down_read_killable() and use it in the VFS's iterate_dir()
     method. (Kirill Tkhai)

   - Convert remaining uses of ACCESS_ONCE() to
     READ_ONCE()/WRITE_ONCE(). Most of the conversion was Coccinelle
     driven. (Mark Rutland, Paul E. McKenney)

   - Get rid of lockless_dereference(), by strengthening Alpha atomics,
     strengthening READ_ONCE() with smp_read_barrier_depends() and thus
     being able to convert users of lockless_dereference() to
     READ_ONCE(). (Will Deacon)

   - Various micro-optimizations:

        - better PV qspinlocks (Waiman Long),
        - better x86 barriers (Michael S. Tsirkin)
        - better x86 refcounts (Kees Cook)

   - ... plus other fixes and enhancements. (Borislav Petkov, Juergen
     Gross, Miguel Bernal Marin)"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  locking/x86: Use LOCK ADD for smp_mb() instead of MFENCE
  rcu: Use lockdep to assert IRQs are disabled/enabled
  netpoll: Use lockdep to assert IRQs are disabled/enabled
  timers/posix-cpu-timers: Use lockdep to assert IRQs are disabled/enabled
  sched/clock, sched/cputime: Use lockdep to assert IRQs are disabled/enabled
  irq_work: Use lockdep to assert IRQs are disabled/enabled
  irq/timings: Use lockdep to assert IRQs are disabled/enabled
  perf/core: Use lockdep to assert IRQs are disabled/enabled
  x86: Use lockdep to assert IRQs are disabled/enabled
  smp/core: Use lockdep to assert IRQs are disabled/enabled
  timers/hrtimer: Use lockdep to assert IRQs are disabled/enabled
  timers/nohz: Use lockdep to assert IRQs are disabled/enabled
  workqueue: Use lockdep to assert IRQs are disabled/enabled
  irq/softirqs: Use lockdep to assert IRQs are disabled/enabled
  locking/lockdep: Add IRQs disabled/enabled assertion APIs: lockdep_assert_irqs_enabled()/disabled()
  locking/pvqspinlock: Implement hybrid PV queued/unfair locks
  locking/rwlocks: Fix comments
  x86/paravirt: Set up the virt_spin_lock_key after static keys get initialized
  block, locking/lockdep: Assign a lock_class per gendisk used for wait_for_completion()
  workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes
  ...
2017-11-13 12:38:26 -08:00
Thomas Gleixner d00a08cf9e irq/work: Use llist_for_each_entry_safe
The llist_for_each_entry() loop in irq_work_run_list() is unsafe because
once the works PENDING bit is cleared it can be requeued on another CPU.

Use llist_for_each_entry_safe() instead.

Fixes: 16c0890dc6 ("irq/work: Don't reinvent the wheel but use existing llist API")
Reported-by:Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petri Latvala <petri.latvala@intel.com>
Link: http://lkml.kernel.org/r/151027307351.14762.4611888896020658384@mail.alporthouse.com
2017-11-12 13:15:14 +01:00
Frederic Weisbecker 3c7169a3bf irq_work: Use lockdep to assert IRQs are disabled/enabled
Use lockdep to check that IRQs are enabled or disabled as expected. This
way the sanity check only shows overhead when concurrency correctness
debug code is enabled.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David S . Miller <davem@davemloft.net>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1509980490-4285-11-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-08 11:13:52 +01:00
Byungchul Park 16c0890dc6 irq/work: Don't reinvent the wheel but use existing llist API
Use the proper llist APIs instead of open-coded variants of them.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1509414414-14987-1-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-31 10:24:39 +01:00
Paul E. McKenney 6733bab7bc irq_work: Map irq_work_on_queue() to irq_work_on() in !SMP
Commit 4788501606 ("irq_work: Implement remote queueing") provides
irq_work_on_queue() only for SMP builds.  However, providing it simplifies
code that submits irq_work to lists of CPUs, eliminating the !SMP special
cases.  This commit therefore maps irq_work_on_queue() to irq_work_on()
in !SMP builds, but validating the specified CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09 14:24:14 -07:00
Peter Zijlstra 90eec103b9 treewide: Remove old email address
There were still a number of references to my old Red Hat email
address in the kernel source. Remove these while keeping the
Red Hat copyright notices intact.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:44:58 +01:00
Christoph Lameter 56e4dea81a percpu: Convert remaining __get_cpu_var uses in 3.18-rcX
During the 3.18 merge period additional __get_cpu_var uses were
added. The patch converts these to this_cpu_ptr().

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
2014-10-29 11:18:18 -04:00
Linus Torvalds 0429fbc0bd Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
Pull percpu consistent-ops changes from Tejun Heo:
 "Way back, before the current percpu allocator was implemented, static
  and dynamic percpu memory areas were allocated and handled separately
  and had their own accessors.  The distinction has been gone for many
  years now; however, the now duplicate two sets of accessors remained
  with the pointer based ones - this_cpu_*() - evolving various other
  operations over time.  During the process, we also accumulated other
  inconsistent operations.

  This pull request contains Christoph's patches to clean up the
  duplicate accessor situation.  __get_cpu_var() uses are replaced with
  with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr().

  Unfortunately, the former sometimes is tricky thanks to C being a bit
  messy with the distinction between lvalues and pointers, which led to
  a rather ugly solution for cpumask_var_t involving the introduction of
  this_cpu_cpumask_var_ptr().

  This converts most of the uses but not all.  Christoph will follow up
  with the remaining conversions in this merge window and hopefully
  remove the obsolete accessors"

* 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits)
  irqchip: Properly fetch the per cpu offset
  percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix
  ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write.
  percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t
  Revert "powerpc: Replace __get_cpu_var uses"
  percpu: Remove __this_cpu_ptr
  clocksource: Replace __this_cpu_ptr with raw_cpu_ptr
  sparc: Replace __get_cpu_var uses
  avr32: Replace __get_cpu_var with __this_cpu_write
  blackfin: Replace __get_cpu_var uses
  tile: Use this_cpu_ptr() for hardware counters
  tile: Replace __get_cpu_var uses
  powerpc: Replace __get_cpu_var uses
  alpha: Replace __get_cpu_var
  ia64: Replace __get_cpu_var uses
  s390: cio driver &__get_cpu_var replacements
  s390: Replace __get_cpu_var uses
  mips: Replace __get_cpu_var uses
  MIPS: Replace __get_cpu_var uses in FPU emulator.
  arm: Replace __this_cpu_ptr with raw_cpu_ptr
  ...
2014-10-15 07:48:18 +02:00
Frederic Weisbecker 76a33061b9 irq_work: Force raised irq work to run on irq work interrupt
The nohz full kick, which restarts the tick when any resource depend
on it, can't be executed anywhere given the operation it does on timers.
If it is called from the scheduler or timers code, chances are that
we run into a deadlock.

This is why we run the nohz full kick from an irq work. That way we make
sure that the kick runs on a virgin context.

However if that's the case when irq work runs in its own dedicated
self-ipi, things are different for the big bunch of archs that don't
support the self triggered way. In order to support them, irq works are
also handled by the timer interrupt as fallback.

Now when irq works run on the timer interrupt, the context isn't blank.
More precisely, they can run in the context of the hrtimer that runs the
tick. But the nohz kick cancels and restarts this hrtimer and cancelling
an hrtimer from itself isn't allowed. This is why we run in an endless
loop:

	Kernel panic - not syncing: Watchdog detected hard LOCKUP on cpu 2
	CPU: 2 PID: 7538 Comm: kworker/u8:8 Not tainted 3.16.0+ #34
	Workqueue: btrfs-endio-write normal_work_helper [btrfs]
	 ffff880244c06c88 000000001b486fe1 ffff880244c06bf0 ffffffff8a7f1e37
	 ffffffff8ac52a18 ffff880244c06c78 ffffffff8a7ef928 0000000000000010
	 ffff880244c06c88 ffff880244c06c20 000000001b486fe1 0000000000000000
	Call Trace:
	 <NMI[<ffffffff8a7f1e37>] dump_stack+0x4e/0x7a
	 [<ffffffff8a7ef928>] panic+0xd4/0x207
	 [<ffffffff8a1450e8>] watchdog_overflow_callback+0x118/0x120
	 [<ffffffff8a186b0e>] __perf_event_overflow+0xae/0x350
	 [<ffffffff8a184f80>] ? perf_event_task_disable+0xa0/0xa0
	 [<ffffffff8a01a4cf>] ? x86_perf_event_set_period+0xbf/0x150
	 [<ffffffff8a187934>] perf_event_overflow+0x14/0x20
	 [<ffffffff8a020386>] intel_pmu_handle_irq+0x206/0x410
	 [<ffffffff8a01937b>] perf_event_nmi_handler+0x2b/0x50
	 [<ffffffff8a007b72>] nmi_handle+0xd2/0x390
	 [<ffffffff8a007aa5>] ? nmi_handle+0x5/0x390
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 [<ffffffff8a008062>] default_do_nmi+0x72/0x1c0
	 [<ffffffff8a008268>] do_nmi+0xb8/0x100
	 [<ffffffff8a7ff66a>] end_repeat_nmi+0x1e/0x2e
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 [<ffffffff8a0cb7f8>] ? match_held_lock+0x8/0x1b0
	 <<EOE><IRQ[<ffffffff8a0ccd2f>] lock_acquired+0xaf/0x450
	 [<ffffffff8a0f74c5>] ? lock_hrtimer_base.isra.20+0x25/0x50
	 [<ffffffff8a7fc678>] _raw_spin_lock_irqsave+0x78/0x90
	 [<ffffffff8a0f74c5>] ? lock_hrtimer_base.isra.20+0x25/0x50
	 [<ffffffff8a0f74c5>] lock_hrtimer_base.isra.20+0x25/0x50
	 [<ffffffff8a0f7723>] hrtimer_try_to_cancel+0x33/0x1e0
	 [<ffffffff8a0f78ea>] hrtimer_cancel+0x1a/0x30
	 [<ffffffff8a109237>] tick_nohz_restart+0x17/0x90
	 [<ffffffff8a10a213>] __tick_nohz_full_check+0xc3/0x100
	 [<ffffffff8a10a25e>] nohz_full_kick_work_func+0xe/0x10
	 [<ffffffff8a17c884>] irq_work_run_list+0x44/0x70
	 [<ffffffff8a17c8da>] irq_work_run+0x2a/0x50
	 [<ffffffff8a0f700b>] update_process_times+0x5b/0x70
	 [<ffffffff8a109005>] tick_sched_handle.isra.21+0x25/0x60
	 [<ffffffff8a109b81>] tick_sched_timer+0x41/0x60
	 [<ffffffff8a0f7aa2>] __run_hrtimer+0x72/0x470
	 [<ffffffff8a109b40>] ? tick_sched_do_timer+0xb0/0xb0
	 [<ffffffff8a0f8707>] hrtimer_interrupt+0x117/0x270
	 [<ffffffff8a034357>] local_apic_timer_interrupt+0x37/0x60
	 [<ffffffff8a80010f>] smp_apic_timer_interrupt+0x3f/0x50
	 [<ffffffff8a7fe52f>] apic_timer_interrupt+0x6f/0x80

To fix this we force non-lazy irq works to run on irq work self-IPIs
when available. That ability of the arch to trigger irq work self IPIs
is available with arch_irq_work_has_interrupt().

Reported-by: Catalin Iacob <iacobcatalin@gmail.com>
Reported-by: Dave Jones <davej@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2014-09-13 18:38:15 +02:00
Christoph Lameter 22127e93c5 time: Replace __get_cpu_var uses
Convert uses of __get_cpu_var for creating a address from a percpu
offset to this_cpu_ptr.

The two cases where get_cpu_var is used to actually access a percpu
variable are changed to use this_cpu_read/raw_cpu_read.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2014-08-26 13:45:44 -04:00
Peter Zijlstra a77353e5eb irq_work: Remove BUG_ON in irq_work_run()
Because of a collision with 8d056c48e4 ("CPU hotplug, smp: flush any
pending IPI callbacks before CPU offline"), which ends up calling
hotplug_cfd()->flush_smp_call_function_queue()->irq_work_run(), which
is not from IRQ context.

And since that already calls irq_work_run() from the hotplug path,
remove our entire hotplug handling.

Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-busatzs2gvz4v62258agipuf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-07-05 11:17:26 +02:00
Frederic Weisbecker 4788501606 irq_work: Implement remote queueing
irq work currently only supports local callbacks. However its code
is mostly ready to run remote callbacks and we have some potential user.

The full nohz subsystem currently open codes its own remote irq work
on top of the scheduler ipi when it wants a CPU to reevaluate its next
tick. However this ad hoc solution bloats the scheduler IPI.

Lets just extend the irq work subsystem to support remote queuing on top
of the generic SMP IPI to handle this kind of user. This shouldn't add
noticeable overhead.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2014-06-16 16:26:54 +02:00
Frederic Weisbecker b93e0b8fa8 irq_work: Split raised and lazy lists
An irq work can be handled from two places: from the tick if the work
carries the "lazy" flag and the tick is periodic, or from a self IPI.

We merge all these works in a single list and we use some per cpu latch
to avoid raising a self-IPI when one is already pending.

Now we could do away with this ugly latch if only the list was only made of
non-lazy works. Just enqueueing a work on the empty list would be enough
to know if we need to raise an IPI or not.

Also we are going to implement remote irq work queuing. Then the per CPU
latch will need to become atomic in the global scope. That's too bad
because, here as well, just enqueueing a work on an empty list of
non-lazy works would be enough to know if we need to raise an IPI or not.

So lets take a way out of this: split the works in two distinct lists,
one for the works that can be handled by the next tick and another
one for those handled by the IPI. Just checking if the latter is empty
when we queue a new work is enough to know if we need to raise an IPI.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2014-06-16 16:26:53 +02:00
Peter Zijlstra cd578abb24 perf/x86: Warn to early_printk() in case irq_work is too slow
On Mon, Feb 10, 2014 at 08:45:16AM -0800, Dave Hansen wrote:
> The reason I coded this up was that NMIs were firing off so fast that
> nothing else was getting a chance to run.  With this patch, at least the
> printk() would come out and I'd have some idea what was going on.

It will start spewing to early_printk() (which is a lot nicer to use
from NMI context too) when it fails to queue the IRQ-work because its
already enqueued.

It does have the false-positive for when two CPUs trigger the warn
concurrently, but that should be rare and some extra clutter on the
early printk shouldn't be a problem.

Cc: hpa@zytor.com
Cc: tglx@linutronix.de
Cc: dzickus@redhat.com
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: mingo@kernel.org
Fixes: 6a02ad66b2 ("perf/x86: Push the duration-logging printk() to IRQ context")
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140211150116.GO27965@twins.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-02-21 21:49:07 +01:00
Frederic Weisbecker 077931446b Merge branch 'nohz/printk-v8' into irq/core
Conflicts:
	kernel/irq_work.c

Add support for printk in full dynticks CPU.

* Don't stop tick with irq works pending. This
fix is generally useful and concerns archs that
can't raise self IPIs.

* Flush irq works before CPU offlining.

* Introduce "lazy" irq works that can wait for the
next tick to be executed, unless it's stopped.

* Implement klogd wake up using irq work. This
removes the ad-hoc printk_tick()/printk_needs_cpu()
hooks and make it working even in dynticks mode.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2013-02-05 00:48:46 +01:00
anish kumar c02cf5f8ed irq_work: Remove return value from the irq_work_queue() function
As no one is using the return value of irq_work_queue(),
so it is better to just make it void.

Signed-off-by: anish kumar <anish198519851985@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
[ Fix stale comments, remove now unnecessary __irq_work_queue() intermediate function ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1359925703-24304-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-02-04 11:50:59 +01:00
Frederic Weisbecker bc6679aef6 irq_work: Make self-IPIs optable
On irq work initialization, let the user choose to define it
as "lazy" or not. "Lazy" means that we don't want to send
an IPI (provided the arch can anyway) when we enqueue this
work but we rather prefer to wait for the next timer tick
to execute our work if possible.

This is going to be a benefit for non-urgent enqueuers
(like printk in the future) that may prefer not to raise
an IPI storm in case of frequent enqueuing on short periods
of time.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-18 01:01:22 +01:00
Steven Rostedt 8aa2accee4 irq_work: Warn if there's still work on cpu_down
If we are in nohz and there's still irq_work to be done when the idle
task is about to go offline, give a nasty warning. Everything should
have been flushed from the CPU_DYING notifier already. Further attempts
to enqueue an irq_work are buggy because irqs are disabled by
__cpu_disable(). The best we can do is to report the issue to the user.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2012-11-17 19:31:16 +01:00
Steven Rostedt c0e980a4bd irq_work: Flush work on CPU_DYING
In order not to offline a CPU with pending irq works, flush the
queue from CPU_DYING. The notifier is called by stop_machine on
the CPU that is going down. The code will not be called from irq context
(so things like get_irq_regs() wont work) but I'm not sure what the
requirements are for irq_work in that regard (Peter?). But irqs are
disabled and the CPU is about to go offline. Might as well flush the work.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2012-11-17 19:31:03 +01:00
Frederic Weisbecker 00b4295910 irq_work: Don't stop the tick with pending works
Don't stop the tick if we have pending irq works on the
queue, otherwise if the arch can't raise self-IPIs, we may not
find an opportunity to execute the pending works for a while.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-17 19:30:39 +01:00
Frederic Weisbecker e0bbe2d80c irq_work: Fix racy check on work pending flag
Work claiming wants to be SMP-safe.

And by the time we try to claim a work, if it is already executing
concurrently on another CPU, we want to succeed the claiming and queue
the work again because the other CPU may have missed the data we wanted
to handle in our work if it's about to complete there.

This scenario is summarized below:

        CPU 1                                   CPU 2
        -----                                   -----
        (flags = 0)
        cmpxchg(flags, 0, IRQ_WORK_FLAGS)
        (flags = 3)
        [...]
        xchg(flags, IRQ_WORK_BUSY)
        (flags = 2)
        func()
                                                if (flags & IRQ_WORK_PENDING)
                                                        (not true)
                                                cmpxchg(flags, flags, IRQ_WORK_FLAGS)
                                                (flags = 3)
                                                [...]
        cmpxchg(flags, IRQ_WORK_BUSY, 0);
        (fail, pending on CPU 2)

This state machine is synchronized using [cmp]xchg() on the flags.
As such, the early IRQ_WORK_PENDING check in CPU 2 above is racy.
By the time we check it, we may be dealing with a stale value because
we aren't using an atomic accessor. As a result, CPU 2 may "see"
that the work is still pending on another CPU while it may be
actually completing the work function exection already, leaving
our data unprocessed.

To fix this, we start by speculating about the value we wish to be
in the work->flags but we only make any conclusion after the value
returned by the cmpxchg() call that either claims the work or let
the current owner handle the pending work for us.

Changelog-heavily-inspired-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Anish Kumar <anish198519851985@gmail.com>
2012-11-14 17:36:32 +01:00
Frederic Weisbecker c8446b75be irq_work: Fix racy IRQ_WORK_BUSY flag setting
The IRQ_WORK_BUSY flag is set right before we execute the
work. Once this flag value is set, the work enters a
claimable state again.

So if we have specific data to compute in our work, we ensure it's
either handled by another CPU or locally by enqueuing the work again.
This state machine is guanranteed by atomic operations on the flags.

So when we set IRQ_WORK_BUSY without using an xchg-like operation,
we break this guarantee as in the following summarized scenario:

        CPU 1                                   CPU 2
        -----                                   -----
                                                (flags = 0)
                                                old_flags = flags;
        (flags = 0)
        cmpxchg(flags, old_flags,
                old_flags | IRQ_WORK_FLAGS)
        (flags = 3)
        [...]
        flags = IRQ_WORK_BUSY
        (flags = 2)
        func()
                                                (sees flags = 3)
                                                cmpxchg(flags, old_flags,
                                                        old_flags | IRQ_WORK_FLAGS)
                                                (give up)

        cmpxchg(flags, 2, 0);
        (flags = 0)

CPU 1 claims a work and executes it, so it sets IRQ_WORK_BUSY and
the work is again in a claimable state. Now CPU 2 has new data to process
and try to claim that work but it may see a stale value of the flags
and think the work is still pending somewhere that will handle our data.
This is because CPU 1 doesn't set IRQ_WORK_BUSY atomically.

As a result, the data expected to be handle by CPU 2 won't get handled.

To fix this, use xchg() to set IRQ_WORK_BUSY, this way we ensure the CPU 2
will see the correct value with cmpxchg() using the expected ordering.

Changelog-heavily-inspired-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Anish Kumar <anish198519851985@gmail.com>
2012-11-14 17:36:05 +01:00
Chris Metcalf ef1f098254 irq_work: fix compile failure on tile from missing include
Building with IRQ_WORK configured results in

kernel/irq_work.c: In function ‘irq_work_run’:
kernel/irq_work.c:110: error: implicit declaration of function ‘irqs_disabled’

The appropriate header just needs to be included.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-04-13 13:15:16 -04:00
Paul Gortmaker 83e3fa6f01 irq_work: fix compile failure on MIPS from system.h split
Builds of the MIPS platform ip32_defconfig fails as of commit
0195c00244 ("Merge tag 'split-asm_system_h ...") because MIPS xchg()
macro uses BUILD_BUG_ON and it was moved in commit b81947c646
("Disintegrate asm/system.h for MIPS").

The root cause is that the system.h split wasn't tested on a baseline
with commit 6c03438ede ("kernel.h: doesn't explicitly use bug.h, so
don't include it.")

Since this file uses BUG code in several other places besides the xchg
call, simply make the inclusion explicit.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-04-02 08:48:04 -07:00
Paul Gortmaker 967d1f9062 kernel: fix two implicit header assumptions in irq_work.c
Up until now, this file was getting percpu.h because nearly every
file was implicitly getting module.h (and all its sub-includes).
But we want to clean that up, so call out percpu.h explicitly.
Otherwise we'll get things like this on an ARM build:

kernel/irq_work.c:48: error: expected declaration specifiers or '...' before 'irq_work_list'
kernel/irq_work.c:48: warning: type defaults to 'int' in declaration of 'DEFINE_PER_CPU'

The same thing was happening for builds on ARM for asm/processor.h

kernel/irq_work.c: In function 'irq_work_sync':
kernel/irq_work.c:166: error: implicit declaration of function 'cpu_relax'

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-10-31 09:20:12 -04:00
Paul Gortmaker 9984de1a5a kernel: Map most files to use export.h instead of module.h
The changed files were only including linux/module.h for the
EXPORT_SYMBOL infrastructure, and nothing else.  Revector them
onto the isolated export header for faster compile times.

Nothing to see here but a whole lot of instances of:

  -#include <linux/module.h>
  +#include <linux/export.h>

This commit is only changing the kernel dir; next targets
will probably be mm, fs, the arch dirs, etc.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-10-31 09:20:12 -04:00
Peter Zijlstra 924f8f5af3 llist: Add llist_next()
So we don't have to expose the struct list_node member.

Cc: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315836348.26517.41.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-10-04 12:43:53 +02:00
Huang Ying 38aaf8090d irq_work: Use llist in the struct irq_work logic
Use llist in irq_work instead of the lock-less linked list
implementation in irq_work to avoid the code duplication.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315461646-1379-6-git-send-email-ying.huang@intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-10-04 12:43:49 +02:00
Christoph Lameter 20b876918c irq_work: Use per cpu atomics instead of regular atomics
The irq work queue is a per cpu object and it is sufficient for
synchronization if per cpu atomics are used. Doing so simplifies
the code and reduces the overhead of the code.

Before:

christoph@linux-2.6$ size kernel/irq_work.o
   text	   data	    bss	    dec	    hex	filename
    451	      8	      1	    460	    1cc	kernel/irq_work.o

After:

christoph@linux-2.6$ size kernel/irq_work.o 
   text	   data	    bss	    dec	    hex	filename
    438	      8	      1	    447	    1bf	kernel/irq_work.o

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Christoph Lameter <cl@linux.com>
2010-12-18 15:54:48 +01:00
Sergio Aguirre 94e8ba7286 irq_work: Drop cmpxchg() result
The compiler warned us about:

 kernel/irq_work.c: In function 'irq_work_run':
 kernel/irq_work.c:148: warning: value computed is not used

Dropping the cmpxchg() result is indeed weird, but correct -
so annotate away the warning.

Signed-off-by: Sergio Aguirre <saaguirre@ti.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1289930567-17828-1-git-send-email-saaguirre@ti.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-11-18 13:18:47 +01:00
Peter Zijlstra e360adbe29 irq_work: Add generic hardirq context callbacks
Provide a mechanism that allows running code in IRQ context. It is
most useful for NMI code that needs to interact with the rest of the
system -- like wakeup a task to drain buffers.

Perf currently has such a mechanism, so extract that and provide it as
a generic feature, independent of perf so that others may also
benefit.

The IRQ context callback is generated through self-IPIs where
possible, or on architectures like powerpc the decrementer (the
built-in timer facility) is set to generate an interrupt immediately.

Architectures that don't have anything like this get to do with a
callback from the timer tick. These architectures can call
irq_work_run() at the tail of any IRQ handlers that might enqueue such
work (like the perf IRQ handler) to avoid undue latencies in
processing the work.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[ various fixes ]
Signed-off-by: Huang Ying <ying.huang@intel.com>
LKML-Reference: <1287036094.7768.291.camel@yhuang-dev>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 19:58:50 +02:00