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path: root/include/linux/workqueue.h
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* workqueue: dump workqueues on sysrq-tTejun Heo2015-03-09
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Workqueues are used extensively throughout the kernel but sometimes it's difficult to debug stalls involving work items because visibility into its inner workings is fairly limited. Although sysrq-t task dump annotates each active worker task with the information on the work item being executed, it is challenging to find out which work items are pending or delayed on which queues and how pools are being managed. This patch implements show_workqueue_state() which dumps all busy workqueues and pools and is called from the sysrq-t handler. At the end of sysrq-t dump, something like the following is printed. Showing busy workqueues and worker pools: ... workqueue filler_wq: flags=0x0 pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 in-flight: 491:filler_workfn, 507:filler_workfn pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=2/256 in-flight: 501:filler_workfn pending: filler_workfn ... workqueue test_wq: flags=0x8 pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 in-flight: 510(RESCUER):test_workfn BAR(69) BAR(500) delayed: test_workfn1 BAR(492), test_workfn2 ... pool 0: cpus=0 node=0 flags=0x0 nice=0 workers=2 manager: 137 pool 2: cpus=1 node=0 flags=0x0 nice=0 workers=3 manager: 469 pool 3: cpus=1 node=0 flags=0x0 nice=-20 workers=2 idle: 16 pool 8: cpus=0-3 flags=0x4 nice=0 workers=2 manager: 62 The above shows that test_wq is executing test_workfn() on pid 510 which is the rescuer and also that there are two tasks 69 and 500 waiting for the work item to finish in flush_work(). As test_wq has max_active of 1, there are two work items for test_workfn1() and test_workfn2() which are delayed till the current work item is finished. In addition, pid 492 is flushing test_workfn1(). The work item for test_workfn() is being executed on pwq of pool 2 which is the normal priority per-cpu pool for CPU 1. The pool has three workers, two of which are executing filler_workfn() for filler_wq and the last one is assuming the manager role trying to create more workers. This extra workqueue state dump will hopefully help chasing down hangs involving workqueues. v3: cpulist_pr_cont() replaced with "%*pbl" printf formatting. v2: As suggested by Andrew, minor formatting change in pr_cont_work(), printk()'s replaced with pr_info()'s, and cpumask printing now uses cpulist_pr_cont(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> CC: Ingo Molnar <mingo@redhat.com>
* workqueue: fix hang involving racing cancel[_delayed]_work_sync()'s for ↵Tejun Heo2015-03-05
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | PREEMPT_NONE cancel[_delayed]_work_sync() are implemented using __cancel_work_timer() which grabs the PENDING bit using try_to_grab_pending() and then flushes the work item with PENDING set to prevent the on-going execution of the work item from requeueing itself. try_to_grab_pending() can always grab PENDING bit without blocking except when someone else is doing the above flushing during cancelation. In that case, try_to_grab_pending() returns -ENOENT. In this case, __cancel_work_timer() currently invokes flush_work(). The assumption is that the completion of the work item is what the other canceling task would be waiting for too and thus waiting for the same condition and retrying should allow forward progress without excessive busy looping Unfortunately, this doesn't work if preemption is disabled or the latter task has real time priority. Let's say task A just got woken up from flush_work() by the completion of the target work item. If, before task A starts executing, task B gets scheduled and invokes __cancel_work_timer() on the same work item, its try_to_grab_pending() will return -ENOENT as the work item is still being canceled by task A and flush_work() will also immediately return false as the work item is no longer executing. This puts task B in a busy loop possibly preventing task A from executing and clearing the canceling state on the work item leading to a hang. task A task B worker executing work __cancel_work_timer() try_to_grab_pending() set work CANCELING flush_work() block for work completion completion, wakes up A __cancel_work_timer() while (forever) { try_to_grab_pending() -ENOENT as work is being canceled flush_work() false as work is no longer executing } This patch removes the possible hang by updating __cancel_work_timer() to explicitly wait for clearing of CANCELING rather than invoking flush_work() after try_to_grab_pending() fails with -ENOENT. Link: http://lkml.kernel.org/g/20150206171156.GA8942@axis.com v3: bit_waitqueue() can't be used for work items defined in vmalloc area. Switched to custom wake function which matches the target work item and exclusive wait and wakeup. v2: v1 used wake_up() on bit_waitqueue() which leads to NULL deref if the target bit waitqueue has wait_bit_queue's on it. Use DEFINE_WAIT_BIT() and __wake_up_bit() instead. Reported by Tomeu Vizoso. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Rabin Vincent <rabin.vincent@axis.com> Cc: Tomeu Vizoso <tomeu.vizoso@gmail.com> Cc: stable@vger.kernel.org Tested-by: Jesper Nilsson <jesper.nilsson@axis.com> Tested-by: Rabin Vincent <rabin.vincent@axis.com>
* workqueue.h: remove loops of single statement macrosValentin Rothberg2015-01-06
| | | | | | | | | | checkpatch.pl complained about two single statement macros in do while (0) loops. The loops and the trailing semicolons are now removed, which makes checkpatch happy and the two macros consistent with the rest of the file. Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: apply __WQ_ORDERED to create_singlethread_workqueue()Tejun Heo2014-09-12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | create_singlethread_workqueue() is a compat interface for single threaded workqueue which maps to ordered workqueue w/ rescuer in the current implementation. create_singlethread_workqueue() currently implemented by invoking alloc_workqueue() w/ appropriate parameters. 8719dceae2f9 ("workqueue: reject adjusting max_active or applying attrs to ordered workqueues") introduced __WQ_ORDERED to protect ordered workqueues against dynamic attribute changes which can break ordering guarantees but forgot to apply it to create_singlethread_workqueue(). This in itself is okay as nobody currently uses dynamic attribute change on workqueues created with create_singlethread_workqueue(). However, 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues") broke singlethreaded guarantee for ordered workqueues through allocating a separate pool_workqueue on each NUMA node by default. A later change 8a2b75384444 ("workqueue: fix ordered workqueues in NUMA setups") fixed it by allocating only one global pool_workqueue if __WQ_ORDERED is set. Combined, the __WQ_ORDERED omission in create_singlethread_workqueue() became critical breaking its single threadedness and ordering guarantee. Let's make create_singlethread_workqueue() wrap alloc_ordered_workqueue() instead so that it inherits __WQ_ORDERED and can implicitly track future ordered_workqueue changes. v2: I missed that __WQ_ORDERED now protects against pwq splitting across NUMA nodes and incorrectly described the patch as a nice-to-have fix to protect against future dynamic attribute usages. Oleg pointed out that this is actually a critical breakage due to 8a2b75384444 ("workqueue: fix ordered workqueues in NUMA setups"). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Mike Anderson <mike.anderson@us.ibm.com> Cc: Oleg Nesterov <onestero@redhat.com> Cc: Gustavo Luiz Duarte <gduarte@redhat.com> Cc: Tomas Henzl <thenzl@redhat.com> Cc: stable@vger.kernel.org Fixes: 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues")
* workqueue: remove unused work_clear_pending()Lai Jiangshan2014-05-22
| | | | | | | | | | | | In 8930caba3dbd ("workqueue: disable irq while manipulating PENDING"), setting last CPU and clearing PENDING got merged into a single operation (set_work_cpu_and_clear_pending()), which resulted that the internal routine work_clear_pending() is not used any more. tj: Minor description tweak. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: remove unused WORK_CPU_ENDLai Jiangshan2014-05-22
| | | | | | | | | | | | | | | WORK_CPU_END is totally unused since 4e8b22bd1a37 ("workqueue: fix pool ID allocation leakage and remove BUILD_BUG_ON() in init_workqueues"). It should be removed. After it is removed, the comment "special cpu IDs" is not precise due to there is only one special CPU ID (WORK_CPU_UNBOUND) left, so we also change this comment to the description for WORK_CPU_UNBOUND. tj: Minor description and comment tweaks. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: declare system_highpri_wqLai Jiangshan2014-05-22
| | | | | | | | | | | system_highpri_wq is exported to modules via EXPORT_SYMBOL_GPL(), but it was forgotten to be declared in workqueue.h. So we add the declaration and a short description for it. tj: Minor comment tweak. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: Remove deprecated system_nrt[_freezable]_wqJingoo Han2014-05-14
| | | | | | | | | | system_nrt[_freezable]_wq were deprecated by 3b07e9c ("workqueue: deprecate system_nrt[_freezable]_wq") and have been deprecated for a long time. In addition, these are not used anymore. So, let's remove these functions. Signed-off-by: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: Remove deprecated flush[_delayed]_work_sync()Jingoo Han2014-05-14
| | | | | | | | | | flush[_delayed]_work_sync() were deprecated by 4382973 ("workqueue: deprecate flush[_delayed]_work_sync()") and have been deprecated for a long time. In addition, these are not used anymore. So, let's remove these functions. Signed-off-by: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* Merge branch 'timers-core-for-linus' of ↵Linus Torvalds2014-04-01
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer changes from Thomas Gleixner: "This assorted collection provides: - A new timer based timer broadcast feature for systems which do not provide a global accessible timer device. That allows those systems to put CPUs into deep idle states where the per cpu timer device stops. - A few NOHZ_FULL related improvements to the timer wheel - The usual updates to timer devices found in ARM SoCs - Small improvements and updates all over the place" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits) tick: Remove code duplication in tick_handle_periodic() tick: Fix spelling mistake in tick_handle_periodic() x86: hpet: Use proper destructor for delayed work workqueue: Provide destroy_delayed_work_on_stack() clocksource: CMT, MTU2, TMU and STI should depend on GENERIC_CLOCKEVENTS timer: Remove code redundancy while calling get_nohz_timer_target() hrtimer: Rearrange comments in the order struct members are declared timer: Use variable head instead of &work_list in __run_timers() clocksource: exynos_mct: silence a static checker warning arm: zynq: Add support for cpufreq arm: zynq: Don't use arm_global_timer with cpufreq clocksource/cadence_ttc: Overhaul clocksource frequency adjustment clocksource/cadence_ttc: Call clockevents_update_freq() with IRQs enabled clocksource: Add Kconfig entries for CMT, MTU2, TMU and STI sh: Remove Kconfig entries for TMU, CMT and MTU2 ARM: shmobile: Remove CMT, TMU and STI Kconfig entries clocksource: armada-370-xp: Use atomic access for shared registers clocksource: orion: Use atomic access for shared registers clocksource: timer-keystone: Delete unnecessary variable clocksource: timer-keystone: introduce clocksource driver for Keystone ...
| * workqueue: Provide destroy_delayed_work_on_stack()Thomas Gleixner2014-03-25
| | | | | | | | | | | | | | | | | | | | | | | | If a delayed or deferrable work is on stack we need to tell debug objects that we are destroying the timer and the work. Otherwise we leak the tracking object. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Acked-by: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/20140323141939.911487677@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | workqueue: remove deprecated WQ_NON_REENTRANTZhangZhen2014-03-29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Tejun Heo has made WQ_NON_REENTRANT useless in the dbf2576e37 ("workqueue: make all workqueues non-reentrant"). So remove its usages and definition. This patch doesn't introduce any behavior changes. tj: minor description updates. Signed-off-by: ZhangZhen <zhenzhang.zhang@huawei.com> Sigend-off-by: Tejun Heo <tj@kernel.org> Acked-by: James Chapman <jchapman@katalix.com> Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
* | workqueue: Spelling s/instensive/intensive/Geert Uytterhoeven2014-03-24
| | | | | | | | | | Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Tejun Heo <tj@kernel.org>
* | workqueue: remove PREPARE_[DELAYED_]WORK()Tejun Heo2014-03-07
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Peter Hurley noticed that since a2c1c57be8d9 ("workqueue: consider work function when searching for busy work items"), a work item which gets assigned a different work function would break out of the non-reentrancy guarantee as workqueue would consider it a different work item. This is fragile and extremely subtle. PREPARE_[DELAYED_]WORK() have never been used widely and its semantics has always been somewhat iffy. If the work item is known not to be on queue when PREPARE_WORK() is called, there's no difference from using INIT_WORK(). If the work item may be queued at the time of PREPARE_WORK(), we can't really tell whether the old or new function will be executed the next time. We really don't want this level of subtlety in workqueue interface for such marginal use cases. The previous patches converted all existing users away from PREPARE_[DELAYED_]WORK(). Let's remove them. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Peter Hurley <peter@hurleysoftware.com> Link: http://lkml.kernel.org/g/1392493119-9277-1-git-send-email-peter@hurleysoftware.com
* | Merge branch 'wq/for-3.14-fixes' into wq/for-3.15Tejun Heo2014-03-07
|\ \ | | | | | | | | | | | | | | | | | | To receive 70044d71d31d ("firewire: don't use PREPARE_DELAYED_WORK"). There will be further related updates in for-3.15 branch. Signed-off-by: Tejun Heo <tj@kernel.org>
| * | workqueue: add args to workqueue lockdep nameLi Zhong2014-02-14
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Tommi noticed a 'funny' lock class name: "%s#5" from a lock acquired in process_one_work(). Maybe #fmt plus #args could be used as the lock_name to give some more information for some fmt string like the above. __builtin_constant_p() check is removed (as there seems no good way to check all the variables in args list). However, by removing the check, it only adds two additional "s for those constants. Some lockdep name examples printed out after the change: lockdep name wq->name "events_long" events_long "%s"("khelper") khelper "xfs-data/%s"mp->m_fsname xfs-data/dm-3 Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* / workqueue: Remove deprecated __cancel_delayed_work()Tan Xiaojun2014-02-18
|/ | | | | | | | | | | | __cancel_delayed_work() was deprecated by 136b5721d75a ("workqueue: deprecate __cancel_delayed_work()") as cancel_delayed_work() was updated so that it could be used from all contexts. Enough time has passed since the deprecation. Let's remove it. tj: description update Signed-off-by: Tan Xiaojun <tanxiaojun@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: mark WQ_NON_REENTRANT deprecatedTejun Heo2013-07-30
| | | | | | | | | dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op but the following patches didn't remove the flag or update the documentation. Let's mark the flag deprecated and update the documentation accordingly. Signed-off-by: Tejun Heo <tj@kernel.org>
* drivers: avoid format strings in names passed to alloc_workqueue()Kees Cook2013-07-03
| | | | | | | | | | | | For the workqueue creation interfaces that do not expect format strings, make sure they cannot accidently be parsed that way. Additionally, clean up calls made with a single parameter that would be handled as a format string. Many callers are passing potentially dynamic string content, so use "%s" in those cases to avoid any potential accidents. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* workqueue: Add system wide power_efficient workqueuesViresh Kumar2013-05-14
| | | | | | | | | | | This patch adds system wide workqueues aligned towards power saving. This is done by allocating them with WQ_UNBOUND flag if 'wq_power_efficient' is set to 'true'. tj: updated comments a bit. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqueuesViresh Kumar2013-05-14
| | | | | | | | | | | | | | | | | | | | | | Workqueues can be performance or power-oriented. Currently, most workqueues are bound to the CPU they were created on. This gives good performance (due to cache effects) at the cost of potentially waking up otherwise idle cores (Idle from scheduler's perspective. Which may or may not be physically idle) just to process some work. To save power, we can allow the work to be rescheduled on a core that is already awake. Workqueues created with the WQ_UNBOUND flag will allow some power savings. However, we don't change the default behaviour of the system. To enable power-saving behaviour, a new config option CONFIG_WQ_POWER_EFFICIENT needs to be turned on. This option can also be overridden by the workqueue.power_efficient boot parameter. tj: Updated config description and comments. Renamed CONFIG_WQ_POWER_EFFICIENT to CONFIG_WQ_POWER_EFFICIENT_DEFAULT. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: include workqueue info when printing debug dump of a worker taskTejun Heo2013-04-30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | One of the problems that arise when converting dedicated custom threadpool to workqueue is that the shared worker pool used by workqueue anonimizes each worker making it more difficult to identify what the worker was doing on which target from the output of sysrq-t or debug dump from oops, BUG() and friends. This patch implements set_worker_desc() which can be called from any workqueue work function to set its description. When the worker task is dumped for whatever reason - sysrq-t, WARN, BUG, oops, lockdep assertion and so on - the description will be printed out together with the workqueue name and the worker function pointer. The printing side is implemented by print_worker_info() which is called from functions in task dump paths - sched_show_task() and dump_stack_print_info(). print_worker_info() can be safely called on any task in any state as long as the task struct itself is accessible. It uses probe_*() functions to access worker fields. It may print garbage if something went very wrong, but it wouldn't cause (another) oops. The description is currently limited to 24bytes including the terminating \0. worker->desc_valid and workder->desc[] are added and the 64 bytes marker which was already incorrect before adding the new fields is moved to the correct position. Here's an example dump with writeback updated to set the bdi name as worker desc. Hardware name: Bochs Modules linked in: Pid: 7, comm: kworker/u9:0 Not tainted 3.9.0-rc1-work+ #1 Workqueue: writeback bdi_writeback_workfn (flush-8:0) ffffffff820a3ab0 ffff88000f6e9cb8 ffffffff81c61845 ffff88000f6e9cf8 ffffffff8108f50f 0000000000000000 0000000000000000 ffff88000cde16b0 ffff88000cde1aa8 ffff88001ee19240 ffff88000f6e9fd8 ffff88000f6e9d08 Call Trace: [<ffffffff81c61845>] dump_stack+0x19/0x1b [<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0 [<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20 [<ffffffff81200150>] bdi_writeback_workfn+0x2a0/0x3b0 ... Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Acked-by: Jan Kara <jack@suse.cz> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* workqueue: update sysfs interface to reflect NUMA awareness and a kernel ↵Tejun Heo2013-04-01
| | | | | | | | | | | | | | | | | | | | | | | | | param to disable NUMA affinity Unbound workqueues are now NUMA aware. Let's add some control knobs and update sysfs interface accordingly. * Add kernel param workqueue.numa_disable which disables NUMA affinity globally. * Replace sysfs file "pool_id" with "pool_ids" which contain node:pool_id pairs. This change is userland-visible but "pool_id" hasn't seen a release yet, so this is okay. * Add a new sysf files "numa" which can toggle NUMA affinity on individual workqueues. This is implemented as attrs->no_numa whichn is special in that it isn't part of a pool's attributes. It only affects how apply_workqueue_attrs() picks which pools to use. After "pool_ids" change, first_pwq() doesn't have any user left. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: inline trivial wrappersTejun Heo2013-03-13
| | | | | | | | | | | | | | | | There's no reason to make these trivial wrappers full (exported) functions. Inline the followings. queue_work() queue_delayed_work() mod_delayed_work() schedule_work_on() schedule_work() schedule_delayed_work_on() schedule_delayed_work() keventd_up() Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: implement current_is_workqueue_rescuer()Tejun Heo2013-03-12
| | | | | | | | Implement a function which queries whether it currently is running off a workqueue rescuer. This will be used to convert writeback to workqueue. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: implement sysfs interface for workqueuesTejun Heo2013-03-12
| | | | | | | | | | | | | | | | | | | | | | | | | There are cases where workqueue users want to expose control knobs to userland. e.g. Unbound workqueues with custom attributes are scheduled to be used for writeback workers and depending on configuration it can be useful to allow admins to tinker with the priority or allowed CPUs. This patch implements workqueue_sysfs_register(), which makes the workqueue visible under /sys/bus/workqueue/devices/WQ_NAME. There currently are two attributes common to both per-cpu and unbound pools and extra attributes for unbound pools including nice level and cpumask. If alloc_workqueue*() is called with WQ_SYSFS, workqueue_sysfs_register() is called automatically as part of workqueue creation. This is the preferred method unless the workqueue user wants to apply workqueue_attrs before making the workqueue visible to userland. v2: Disallow exposing ordered workqueues as ordered workqueues can't be tuned in any way. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: reject adjusting max_active or applying attrs to ordered workqueuesTejun Heo2013-03-12
| | | | | | | | | | | | | | Adjusting max_active of or applying new workqueue_attrs to an ordered workqueue breaks its ordering guarantee. The former is obvious. The latter is because applying attrs creates a new pwq (pool_workqueue) and there is no ordering constraint between the old and new pwqs. Make apply_workqueue_attrs() and workqueue_set_max_active() trigger WARN_ON() if those operations are requested on an ordered workqueue and fail / ignore respectively. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: make it clear that WQ_DRAINING is an internal flagTejun Heo2013-03-12
| | | | | | | | We're gonna add another internal WQ flag. Let's make the distinction clear. Prefix WQ_DRAINING with __ and move it to bit 16. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: implement apply_workqueue_attrs()Tejun Heo2013-03-12
| | | | | | | | | | | | | | | | | | | | | | | | | | Implement apply_workqueue_attrs() which applies workqueue_attrs to the specified unbound workqueue by creating a new pwq (pool_workqueue) linked to worker_pool with the specified attributes. A new pwq is linked at the head of wq->pwqs instead of tail and __queue_work() verifies that the first unbound pwq has positive refcnt before choosing it for the actual queueing. This is to cover the case where creation of a new pwq races with queueing. As base ref on a pwq won't be dropped without making another pwq the first one, __queue_work() is guaranteed to make progress and not add work item to a dead pwq. init_and_link_pwq() is updated to return the last first pwq the new pwq replaced, which is put by apply_workqueue_attrs(). Note that apply_workqueue_attrs() is almost identical to unbound pwq part of alloc_and_link_pwqs(). The only difference is that there is no previous first pwq. apply_workqueue_attrs() is implemented to handle such cases and replaces unbound pwq handling in alloc_and_link_pwqs(). Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: drop WQ_RESCUER and test workqueue->rescuer for NULL insteadTejun Heo2013-03-12
| | | | | | | | | | | | | | | | | | | | | WQ_RESCUER is superflous. WQ_MEM_RECLAIM indicates that the user wants a rescuer and testing wq->rescuer for NULL can answer whether a given workqueue has a rescuer or not. Drop WQ_RESCUER and test wq->rescuer directly. This will help simplifying __alloc_workqueue_key() failure path by allowing it to use destroy_workqueue() on a partially constructed workqueue, which in turn will help implementing dynamic management of pool_workqueues. While at it, clear wq->rescuer after freeing it in destroy_workqueue(). This is a precaution as scheduled changes will make destruction more complex. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: introduce workqueue_attrsTejun Heo2013-03-12
| | | | | | | | | | | | | | | | | | | | | | | | | | | Introduce struct workqueue_attrs which carries worker attributes - currently the nice level and allowed cpumask along with helper routines alloc_workqueue_attrs() and free_workqueue_attrs(). Each worker_pool now carries ->attrs describing the attributes of its workers. All functions dealing with cpumask and nice level of workers are updated to follow worker_pool->attrs instead of determining them from other characteristics of the worker_pool, and init_workqueues() is updated to set worker_pool->attrs appropriately for all standard pools. Note that create_worker() is updated to always perform set_user_nice() and use set_cpus_allowed_ptr() combined with manual assertion of PF_THREAD_BOUND instead of kthread_bind(). This simplifies handling random attributes without affecting the outcome. This patch doesn't introduce any behavior changes. v2: Missing cpumask_var_t definition caused build failure on some archs. linux/cpumask.h included. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: kbuild test robot <fengguang.wu@intel.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: consistently use int for @cpu variablesTejun Heo2013-03-12
| | | | | | | | | | | | Workqueue is mixing unsigned int and int for @cpu variables. There's no point in using unsigned int for cpus - many of cpu related APIs take int anyway. Consistently use int for @cpu variables so that we can use negative values to mark special ones. This patch doesn't introduce any visible behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: allow more off-queue flag spaceLai Jiangshan2013-03-04
| | | | | | | | | | | | | | | | | | | | When a work item is off-queue, its work->data contains WORK_STRUCT_* and WORK_OFFQ_* flags. As WORK_OFFQ_* flags are used only while a work item is off-queue, it can occupy bits of work->data which aren't used while off-queue. WORK_OFFQ_* currently only use bits used by on-queue CWQ pointer. As color bits aren't used while off-queue, there's no reason to not use them. Lower WORK_OFFQ_FLAG_BASE from WORK_STRUCT_FLAG_BITS to WORK_STRUCT_COLOR_SHIFT thus giving 4 more bits to off-queue flag space which is also used to record worker_pool ID while off-queue. This doesn't introduce any visible behavior difference. tj: Rewrote the description. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: rename cpu_workqueue to pool_workqueueTejun Heo2013-02-13
| | | | | | | | | | | | | | | | | workqueue has moved away from global_cwqs to worker_pools and with the scheduled custom worker pools, wforkqueues will be associated with pools which don't have anything to do with CPUs. The workqueue code went through significant amount of changes recently and mass renaming isn't likely to hurt much additionally. Let's replace 'cpu' with 'pool' so that it reflects the current design. * s/struct cpu_workqueue_struct/struct pool_workqueue/ * s/cpu_wq/pool_wq/ * s/cwq/pwq/ This patch is purely cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: add delayed_work->wq to simplify reentrancy handlingLai Jiangshan2013-02-06
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To avoid executing the same work item from multiple CPUs concurrently, a work_struct records the last pool it was on in its ->data so that, on the next queueing, the pool can be queried to determine whether the work item is still executing or not. A delayed_work goes through timer before actually being queued on the target workqueue and the timer needs to know the target workqueue and CPU. This is currently achieved by modifying delayed_work->work.data such that it points to the cwq which points to the target workqueue and the last CPU the work item was on. __queue_delayed_work() extracts the last CPU from delayed_work->work.data and then combines it with the target workqueue to create new work.data. The only thing this rather ugly hack achieves is encoding the target workqueue into delayed_work->work.data without using a separate field, which could be a trade off one can make; unfortunately, this entangles work->data management between regular workqueue and delayed_work code by setting cwq pointer before the work item is actually queued and becomes a hindrance for further improvements of work->data handling. This can be easily made sane by adding a target workqueue field to delayed_work. While delayed_work is used widely in the kernel and this does make it a bit larger (<5%), I think this is the right trade-off especially given the prospect of much saner handling of work->data which currently involves quite tricky memory barrier dancing, and don't expect to see any measureable effect. Add delayed_work->wq and drop the delayed_work->work.data overloading. tj: Rewrote the description. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: replace WORK_CPU_NONE/LAST with WORK_CPU_ENDLai Jiangshan2013-02-06
| | | | | | | | | | | | | | | | | | | | Now that workqueue has moved away from gcwqs, workqueue no longer has the need to have a CPU identifier indicating "no cpu associated" - we now use WORK_OFFQ_POOL_NONE instead - and most uses of WORK_CPU_NONE are gone. The only left usage is as the end marker for for_each_*wq*() iterators, where the name WORK_CPU_NONE is confusing w/o actual WORK_CPU_NONE usages. Similarly, WORK_CPU_LAST which equals WORK_CPU_NONE no longer makes sense. Replace both WORK_CPU_NONE and LAST with WORK_CPU_END. This patch doesn't introduce any functional difference. tj: s/WORK_CPU_LAST/WORK_CPU_END/ and rewrote the description. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: record pool ID instead of CPU in work->data when off-queueTejun Heo2013-01-24
| | | | | | | | | | | | | | | | | | | | | | Currently, when a work item is off-queue, work->data records the CPU it was last on, which is used to locate the last executing instance for non-reentrance, flushing, etc. We're in the process of removing global_cwq and making worker_pool the top level abstraction. This patch makes work->data point to the pool it was last associated with instead of CPU. After the previous WORK_OFFQ_POOL_CPU and worker_poo->id additions, the conversion is fairly straight-forward. WORK_OFFQ constants and functions are modified to record and read back pool ID instead. worker_pool_by_id() is added to allow looking up pool from ID. get_work_pool() replaces get_work_gcwq(), which is reimplemented using get_work_pool(). get_work_pool_id() replaces work_cpu(). This patch shouldn't introduce any observable behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: introduce WORK_OFFQ_CPU_NONETejun Heo2013-01-24
| | | | | | | | | | | | | | Currently, when a work item is off queue, high bits of its data encodes the last CPU it was on. This is scheduled to be changed to pool ID, which will make it impossible to use WORK_CPU_NONE to indicate no association. This patch limits the number of bits which are used for off-queue cpu number to 31 (so that the max fits in an int) and uses the highest possible value - WORK_OFFQ_CPU_NONE - to indicate no association. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: unexport work_cpu()Tejun Heo2013-01-24
| | | | | | | | This function no longer has any external users. Unexport it. It will be removed later on. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
* workqueue: deprecate __cancel_delayed_work()Tejun Heo2012-08-21
| | | | | | | | | | | | | Now that cancel_delayed_work() can be safely called from IRQ handlers, there's no reason to use __cancel_delayed_work(). Use cancel_delayed_work() instead of __cancel_delayed_work() and mark the latter deprecated. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Jens Axboe <axboe@kernel.dk> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Roland Dreier <roland@kernel.org> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
* workqueue: reimplement cancel_delayed_work() using try_to_grab_pending()Tejun Heo2012-08-21
| | | | | | | | | | | | | | | | | | | | | | cancel_delayed_work() can't be called from IRQ handlers due to its use of del_timer_sync() and can't cancel work items which are already transferred from timer to worklist. Also, unlike other flush and cancel functions, a canceled delayed_work would still point to the last associated cpu_workqueue. If the workqueue is destroyed afterwards and the work item is re-used on a different workqueue, the queueing code can oops trying to dereference already freed cpu_workqueue. This patch reimplements cancel_delayed_work() using try_to_grab_pending() and set_work_cpu_and_clear_pending(). This allows the function to be called from IRQ handlers and makes its behavior consistent with other flush / cancel functions. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* workqueue: use irqsafe timer for delayed_workTejun Heo2012-08-21
| | | | | | | | | | | | Up to now, for delayed_works, try_to_grab_pending() couldn't be used from IRQ handlers because IRQs may happen while delayed_work_timer_fn() is in progress leading to indefinite -EAGAIN. This patch makes delayed_work use the new TIMER_IRQSAFE flag for delayed_work->timer. This makes try_to_grab_pending() and thus mod_delayed_work_on() safe to call from IRQ handlers. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: clean up delayed_work initializers and add missing oneTejun Heo2012-08-21
| | | | | | | | | Reimplement delayed_work initializers using new timer initializers which take timer flags. This reduces code duplications and will ease further initializer changes. This patch also adds a missing initializer - INIT_DEFERRABLE_WORK_ONSTACK(). Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: make deferrable delayed_work initializer names consistentTejun Heo2012-08-21
| | | | | | | | | | | | | | | | | | Initalizers for deferrable delayed_work are confused. * __DEFERRED_WORK_INITIALIZER() * DECLARE_DEFERRED_WORK() * INIT_DELAYED_WORK_DEFERRABLE() Rename them to * __DEFERRABLE_WORK_INITIALIZER() * DECLARE_DEFERRABLE_WORK() * INIT_DEFERRABLE_WORK() This patch doesn't cause any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: cosmetic whitespace updates for macro definitionsTejun Heo2012-08-21
| | | | | | | | | Consistently use the last tab position for '\' line continuation in complex macro definitions. This is to help the following patches. This patch is cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: deprecate system_nrt[_freezable]_wqTejun Heo2012-08-20
| | | | | | | | | | | | | | | | | | | | | | system_nrt[_freezable]_wq are now spurious. Mark them deprecated and convert all users to system[_freezable]_wq. If you're cc'd and wondering what's going on: Now all workqueues are non-reentrant, so there's no reason to use system_nrt[_freezable]_wq. Please use system[_freezable]_wq instead. This patch doesn't make any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-By: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: David Airlie <airlied@linux.ie> Cc: Jiri Kosina <jkosina@suse.cz> Cc: "David S. Miller" <davem@davemloft.net> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: David Howells <dhowells@redhat.com>
* workqueue: deprecate flush[_delayed]_work_sync()Tejun Heo2012-08-20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | flush[_delayed]_work_sync() are now spurious. Mark them deprecated and convert all users to flush[_delayed]_work(). If you're cc'd and wondering what's going on: Now all workqueues are non-reentrant and the regular flushes guarantee that the work item is not pending or running on any CPU on return, so there's no reason to use the sync flushes at all and they're going away. This patch doesn't make any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Ian Campbell <ian.campbell@citrix.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Mattia Dongili <malattia@linux.it> Cc: Kent Yoder <key@linux.vnet.ibm.com> Cc: David Airlie <airlied@linux.ie> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Karsten Keil <isdn@linux-pingi.de> Cc: Bryan Wu <bryan.wu@canonical.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Alasdair Kergon <agk@redhat.com> Cc: Mauro Carvalho Chehab <mchehab@infradead.org> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Cc: David Woodhouse <dwmw2@infradead.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: linux-wireless@vger.kernel.org Cc: Anton Vorontsov <cbou@mail.ru> Cc: Sangbeom Kim <sbkim73@samsung.com> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Takashi Iwai <tiwai@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Petr Vandrovec <petr@vandrovec.name> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Avi Kivity <avi@redhat.com>
* workqueue: gut system_nrt[_freezable]_wq()Tejun Heo2012-08-20
| | | | | | | | | Now that all workqueues are non-reentrant, system[_freezable]_wq() are equivalent to system_nrt[_freezable]_wq(). Replace the latter with wrappers around system[_freezable]_wq(). The wrapping goes through inline functions so that __deprecated can be added easily. Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: gut flush[_delayed]_work_sync()Tejun Heo2012-08-20
| | | | | | | | | | | | | | Now that all workqueues are non-reentrant, flush[_delayed]_work_sync() are equivalent to flush[_delayed]_work(). Drop the separate implementation and make them thin wrappers around flush[_delayed]_work(). * start_flush_work() no longer takes @wait_executing as the only left user - flush_work() - always sets it to %true. * __cancel_work_timer() uses flush_work() instead of wait_on_work(). Signed-off-by: Tejun Heo <tj@kernel.org>
* workqueue: fix CPU binding of flush_delayed_work[_sync]()Tejun Heo2012-08-13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | delayed_work encodes the workqueue to use and the last CPU in delayed_work->work.data while it's on timer. The target CPU is implicitly recorded as the CPU the timer is queued on and delayed_work_timer_fn() queues delayed_work->work to the CPU it is running on. Unfortunately, this leaves flush_delayed_work[_sync]() no way to find out which CPU the delayed_work was queued for when they try to re-queue after killing the timer. Currently, it chooses the local CPU flush is running on. This can unexpectedly move a delayed_work queued on a specific CPU to another CPU and lead to subtle errors. There isn't much point in trying to save several bytes in struct delayed_work, which is already close to a hundred bytes on 64bit with all debug options turned off. This patch adds delayed_work->cpu to remember the CPU it's queued for. Note that if the timer is migrated during CPU down, the work item could be queued to the downed global_cwq after this change. As a detached global_cwq behaves like an unbound one, this doesn't change much for the delayed_work. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org>