kernel/include/linux/workqueue.h, branch linux-2.6.22.y

revert "cancel_delayed_work: use del_timer() instead of del_timer_sync()"

2007-05-18T15:17:17Z

As pointed out by Jarek Poplawski, the patch [WORKQUEUE]: cancel_delayed_work: use del_timer() instead of del_timer_sync() commit: 071b638689464c6b39407025eedd810d5b5e6f5d was wrong, it was merged by mistake after that. From the changelog: after this patch: ... delayed_work_timer_fn->__queue_work() in progress. The latter doesn't differ from the caller's POV, it does make a difference if the caller calls flush_workqueue() after cancel_delayed_work(), in that case flush_workqueue() can miss this work_struct. Signed-off-by: Oleg Nesterov Cc: Jarek Poplawski Cc: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

make freezeable workqueues singlethread

2007-05-17T12:23:05Z

It is a known fact that freezeable multithreaded workqueues doesn't like CPU_DEAD. We keep them only for the incoming CPU-hotplug rework. Sadly, we can't just kill create_freezeable_workqueue() right now, make them singlethread. Signed-off-by: Oleg Nesterov Cc: "Rafael J. Wysocki" Cc: Gautham R Shenoy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

unify flush_work/flush_work_keventd and rename it to cancel_work_sync

2007-05-09T19:30:53Z

flush_work(wq, work) doesn't need the first parameter, we can use cwq->wq (this was possible from the very beginnig, I missed this). So we can unify flush_work_keventd and flush_work. Also, rename flush_work() to cancel_work_sync() and fix all callers. Perhaps this is not the best name, but "flush_work" is really bad. (akpm: this is why the earlier patches bypassed maintainers) Signed-off-by: Oleg Nesterov Cc: Jeff Garzik Cc: "David S. Miller" Cc: Jens Axboe Cc: Tejun Heo Cc: Auke Kok , Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

workqueue: kill NOAUTOREL works

2007-05-09T19:30:52Z

We don't have any users, and it is not so trivial to use NOAUTOREL works correctly. It is better to simplify API. Delete NOAUTOREL support and rename work_release to work_clear_pending to avoid a confusion. Signed-off-by: Oleg Nesterov Acked-by: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

make cancel_rearming_delayed_work() work on any workqueue, not just keventd_wq

2007-05-09T19:30:52Z

cancel_rearming_delayed_workqueue(wq, dwork) doesn't need the first parameter. We don't hang on un-queued dwork any longer, and work->data doesn't change its type. This means we can always figure out "wq" from dwork when it is needed. Remove this parameter, and rename the function to cancel_rearming_delayed_work(). Re-create an inline "obsolete" cancel_rearming_delayed_workqueue(wq) which just calls cancel_rearming_delayed_work(). Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

workqueue: kill run_scheduled_work()

2007-05-09T19:30:52Z

Because it has no callers. Actually, I think the whole idea of run_scheduled_work() was not right, not good to mix "unqueue this work and execute its ->func()" in one function. Signed-off-by: Oleg Nesterov Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

implement flush_work()

2007-05-09T19:30:50Z

A basic problem with flush_scheduled_work() is that it blocks behind _all_ presently-queued works, rather than just the work whcih the caller wants to flush. If the caller holds some lock, and if one of the queued work happens to want that lock as well then accidental deadlocks can occur. One example of this is the phy layer: it wants to flush work while holding rtnl_lock(). But if a linkwatch event happens to be queued, the phy code will deadlock because the linkwatch callback function takes rtnl_lock. So we implement a new function which will flush a *single* work - just the one which the caller wants to free up. Thus we avoid the accidental deadlocks which can arise from unrelated subsystems' callbacks taking shared locks. flush_work() non-blockingly dequeues the work_struct which we want to kill, then it waits for its handler to complete on all CPUs. Add ->current_work to the "struct cpu_workqueue_struct", it points to currently running "struct work_struct". When flush_work(work) detects ->current_work == work, it inserts a barrier at the _head_ of ->worklist (and thus right _after_ that work) and waits for completition. This means that the next work fired on that CPU will be this barrier, or another barrier queued by concurrent flush_work(), so the caller of flush_work() will be woken before any "regular" work has a chance to run. When wait_on_work() unlocks workqueue_mutex (or whatever we choose to protect against CPU hotplug), CPU may go away. But in that case take_over_work() will move a barrier we queued to another CPU, it will be fired sometime, and wait_on_work() will be woken. Actually, we are doing cleanup_workqueue_thread()->kthread_stop() before take_over_work(), so cwq->thread should complete its ->worklist (and thus the barrier), because currently we don't check kthread_should_stop() in run_workqueue(). But even if we did, everything should be ok. [akpm@osdl.org: cleanup] [akpm@osdl.org: add flush_work_keventd() wrapper] Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Add a new deferrable delayed work init

2007-05-08T18:15:05Z

Add a new deferrable delayed work init. This can be used to schedule work that are 'unimportant' when CPU is idle and can be called later, when CPU eventually comes out of idle. Use this init in cpufreq ondemand governor. Signed-off-by: Venkatesh Pallipadi Cc: Dave Jones Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[WORKQUEUE]: cancel_delayed_work: use del_timer() instead of del_timer_sync()

2007-04-26T22:45:32Z

del_timer_sync() buys nothing for cancel_delayed_work(), but it is less efficient since it locks the timer unconditionally, and may wait for the completion of the delayed_work_timer_fn(). cancel_delayed_work() == 0 means: before this patch: work->func may still be running or queued after this patch: work->func may still be running or queued, or delayed_work_timer_fn->__queue_work() in progress. The latter doesn't differ from the caller's POV, delayed_work_timer_fn() is called with _PENDING bit set. cancel_delayed_work() == 1 with this patch adds a new possibility: delayed_work->work was cancelled, but delayed_work_timer_fn is still running (this is only possible for the re-arming works on single-threaded workqueue). In this case the timer was re-started by work->func(), nobody else can do this. This in turn means that delayed_work_timer_fn has already passed __queue_work() (and wont't touch delayed_work) because nobody else can queue delayed_work->work. Signed-off-by: Oleg Nesterov Signed-Off-By: David Howells Signed-off-by: David S. Miller

Make workqueue bit operations work on "atomic_long_t"

2006-12-16T17:53:50Z

On architectures where the atomicity of the bit operations is handled by external means (ie a separate spinlock to protect concurrent accesses), just doing a direct assignment on the workqueue data field (as done by commit 4594bf159f1962cec3b727954b7c598b07e2e737) can cause the assignment to be lost due to lack of serialization with the bitops on the same word. So we need to serialize the assignment with the locks on those architectures (notably older ARM chips, PA-RISC and sparc32). So rather than using an "unsigned long", let's use "atomic_long_t", which already has a safe assignment operation (atomic_long_set()) on such architectures. This requires that the atomic operations use the same atomicity locks as the bit operations do, but that is largely the case anyway. Sparc32 will probably need fixing. Architectures (including modern ARM with LL/SC) that implement sane atomic operations for SMP won't see any of this matter. Cc: Russell King Cc: David Howells Cc: David Miller Cc: Matthew Wilcox Cc: Linux Arch Maintainers Cc: Andrew Morton Signed-off-by: Linus Torvalds