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* trace: Add trace_ipi_send_cpu()Peter Zijlstra2023-03-241-4/+2
| | | | | | | | | Because copying cpumasks around when targeting a single CPU is a bit daft... Tested-and-reviewed-by: Valentin Schneider <vschneid@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20230322103004.GA571242%40hirez.programming.kicks-ass.net
* irq_work: Trace self-IPIs sent via arch_irq_work_raise()Valentin Schneider2023-03-241-1/+13
| | | | | | | | | | | IPIs sent to remote CPUs via irq_work_queue_on() are now covered by trace_ipi_send_cpumask(), add another instance of the tracepoint to cover self-IPIs. Signed-off-by: Valentin Schneider <vschneid@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20230307143558.294354-5-vschneid@redhat.com
* irq_work: use kasan_record_aux_stack_noalloc() record callstackZqiang2022-04-151-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RTSebastian Andrzej Siewior2021-10-151-2/+4
| | | | | | | | | | | | 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
* irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RTSebastian Andrzej Siewior2021-10-151-12/+106
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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
* irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.Sebastian Andrzej Siewior2021-10-151-0/+10
| | | | | | | | | | | | | | | | | | 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
* irq_work: Make irq_work_queue() NMI-safe againPeter Zijlstra2021-06-101-3/+0
| | | | | | | | | | | Someone carelessly put NMI unsafe code in irq_work_queue(), breaking just about every single user. Also, someone has a terrible comment style. Fixes: e2b5bcf9f5ba ("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
* irq_work: record irq_work_queue() call stackZqiang2021-04-301-1/+6
| | | | | | | | | | | | | | | | | | | 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>
* irq_work: Optimize irq_work_single()Peter Zijlstra2020-11-241-12/+17
| | | | | | | 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>
* irq_work: CleanupPeter Zijlstra2020-11-241-9/+9
| | | | | | | | 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>
* irq_work, smp: Allow irq_work on call_single_queuePeter Zijlstra2020-05-281-24/+29
| | | | | | | | | | | | | | | | 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
* lockdep: Annotate irq_workSebastian Andrzej Siewior2020-03-211-0/+2
| | | | | | | | | | | | | | 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
* irq_work: Fix IRQ_WORK_BUSY bit clearingFrederic Weisbecker2019-11-151-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: feb4a51323ba ("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
* irq_work: Slightly simplify IRQ_WORK_PENDING clearingFrederic Weisbecker2019-11-111-4/+3
| | | | | | | | | | | | | | 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>
* irq_work: Fix irq_work_claim() memory orderingFrederic Weisbecker2019-11-111-15/+7
| | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: Convert flags to atomic_tFrederic Weisbecker2019-11-111-9/+9
| | | | | | | | | | | | | | | | | 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>
* treewide: Add SPDX license identifier for missed filesThomas Gleixner2019-05-211-0/+1
| | | | | | | | | | | | | | | | | 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>
* irq_work: Do not raise an IPI when queueing work on the local CPUNicholas Piggin2019-04-181-33/+42
| | | | | | | | | | | | | | | | | | | | | | | | 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>
* irq/work: Improve the flag definitionsBartosz Golaszewski2018-01-081-1/+1
| | | | | | | | | | | | | | | | | | | 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>
* Merge branch 'irq-core-for-linus' of ↵Linus Torvalds2017-11-141-7/+3
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 ...
| * irq/work: Use llist_for_each_entry_safeThomas Gleixner2017-11-121-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: 16c0890dc66d ("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
| * irq/work: Don't reinvent the wheel but use existing llist APIByungchul Park2017-10-311-5/+1
| | | | | | | | | | | | | | | | | | | | | | | | 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>
* | Merge branch 'locking-core-for-linus' of ↵Linus Torvalds2017-11-131-1/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 ...
| * | irq_work: Use lockdep to assert IRQs are disabled/enabledFrederic Weisbecker2017-11-081-1/+1
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* / irq_work: Map irq_work_on_queue() to irq_work_on() in !SMPPaul E. McKenney2017-10-091-3/+6
|/ | | | | | | | | | Commit 478850160636 ("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>
* treewide: Remove old email addressPeter Zijlstra2015-11-231-1/+1
| | | | | | | | | | | | | | | | | 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>
* percpu: Convert remaining __get_cpu_var uses in 3.18-rcXChristoph Lameter2014-10-291-2/+2
| | | | | | | | | | 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>
* Merge branch 'for-3.18-consistent-ops' of ↵Linus Torvalds2014-10-151-6/+6
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 ...
| * time: Replace __get_cpu_var usesChristoph Lameter2014-08-261-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | 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>
* | irq_work: Force raised irq work to run on irq work interruptFrederic Weisbecker2014-09-131-2/+13
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: Remove BUG_ON in irq_work_run()Peter Zijlstra2014-07-051-42/+4
| | | | | | | | | | | | | | | | | | | Because of a collision with 8d056c48e486 ("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>
* irq_work: Implement remote queueingFrederic Weisbecker2014-06-161-1/+24
| | | | | | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: Split raised and lazy listsFrederic Weisbecker2014-06-161-28/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* perf/x86: Warn to early_printk() in case irq_work is too slowPeter Zijlstra2014-02-211-2/+4
| | | | | | | | | | | | | | | | | | | | | | | | | 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: 6a02ad66b2c4 ("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>
* Merge branch 'nohz/printk-v8' into irq/coreFrederic Weisbecker2013-02-051-26/+86
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * irq_work: Make self-IPIs optableFrederic Weisbecker2012-11-181-20/+27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * irq_work: Warn if there's still work on cpu_downSteven Rostedt2012-11-171-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * irq_work: Flush work on CPU_DYINGSteven Rostedt2012-11-171-6/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * irq_work: Don't stop the tick with pending worksFrederic Weisbecker2012-11-171-0/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | irq_work: Remove return value from the irq_work_queue() functionanish kumar2013-02-041-21/+10
|/ | | | | | | | | | | | 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>
* irq_work: Fix racy check on work pending flagFrederic Weisbecker2012-11-141-5/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: Fix racy IRQ_WORK_BUSY flag settingFrederic Weisbecker2012-11-141-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: fix compile failure on tile from missing includeChris Metcalf2012-04-131-0/+1
| | | | | | | | | | | | 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>
* irq_work: fix compile failure on MIPS from system.h splitPaul Gortmaker2012-04-021-0/+1
| | | | | | | | | | | | | | | | | | Builds of the MIPS platform ip32_defconfig fails as of commit 0195c00244dc ("Merge tag 'split-asm_system_h ...") because MIPS xchg() macro uses BUILD_BUG_ON and it was moved in commit b81947c646bf ("Disintegrate asm/system.h for MIPS"). The root cause is that the system.h split wasn't tested on a baseline with commit 6c03438edeb5 ("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>
* kernel: fix two implicit header assumptions in irq_work.cPaul Gortmaker2011-10-311-0/+2
| | | | | | | | | | | | | | | | | 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>
* kernel: Map most files to use export.h instead of module.hPaul Gortmaker2011-10-311-1/+1
| | | | | | | | | | | | | | | | 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>
* llist: Add llist_next()Peter Zijlstra2011-10-041-1/+1
| | | | | | | | | | 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>
* irq_work: Use llist in the struct irq_work logicHuang Ying2011-10-041-58/+33
| | | | | | | | | | 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>
* irq_work: Use per cpu atomics instead of regular atomicsChristoph Lameter2010-12-181-9/+9
| | | | | | | | | | | | | | | | | | | | | | 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>
* irq_work: Drop cmpxchg() resultSergio Aguirre2010-11-181-1/+3
| | | | | | | | | | | | | | | | | | 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>
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