linux/kernel/workqueue.c, branch v2.6.24

lockdep: fix workqueue creation API lockdep interaction

2008-01-16T08:51:58Z

Dave Young reported warnings from lockdep that the workqueue API can sometimes try to register lockdep classes with the same key but different names. This is not permitted in lockdep. Unfortunately, I was unaware of that restriction when I wrote the code to debug workqueue problems with lockdep and used the workqueue name as the lockdep class name. This can obviously lead to the problem if the workqueue name is dynamic. This patch solves the problem by always using a constant name for the workqueue's lockdep class, namely either the constant name that was passed in or a string consisting of the variable name. Signed-off-by: Johannes Berg Signed-off-by: Ingo Molnar Signed-off-by: Peter Zijlstra

Use helpers to obtain task pid in printks

2007-10-19T18:53:43Z

The task_struct->pid member is going to be deprecated, so start using the helpers (task_pid_nr/task_pid_vnr/task_pid_nr_ns) in the kernel. The first thing to start with is the pid, printed to dmesg - in this case we may safely use task_pid_nr(). Besides, printks produce more (much more) than a half of all the explicit pid usage. [akpm@linux-foundation.org: git-drm went and changed lots of stuff] Signed-off-by: Pavel Emelyanov Cc: Dave Airlie Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

workqueue: debug flushing deadlocks with lockdep

2007-10-19T18:53:38Z

In the following scenario: code path 1: my_function() -> lock(L1); ...; flush_workqueue(); ... code path 2: run_workqueue() -> my_work() -> ...; lock(L1); ... you can get a deadlock when my_work() is queued or running but my_function() has acquired L1 already. This patch adds a pseudo-lock to each workqueue to make lockdep warn about this scenario. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Johannes Berg Acked-by: Oleg Nesterov Acked-by: Ingo Molnar Acked-by: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

fix bogus hotplug cpu warning

2007-08-27T17:27:48Z

Fix bogus DEBUG_PREEMPT warning on x86_64, when cpu brought online after bootup: current_is_keventd is right to note its use of smp_processor_id is preempt-safe, but should use raw_smp_processor_id to avoid the warning. Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds

destroy_workqueue() can livelock

2007-07-17T17:23:03Z

Pointed out by Michal Schmidt . The bug was introduced in 2.6.22 by me. cleanup_workqueue_thread() does flush_cpu_workqueue(cwq) in a loop until ->worklist becomes empty. This is live-lockable, a re-niced caller can get CPU after wake_up() and insert a new barrier before the lower-priority cwq->thread has a chance to clear ->current_work. Change cleanup_workqueue_thread() to do flush_cpu_workqueue(cwq) only once. We can rely on the fact that run_workqueue() won't return until it flushes all works. So it is safe to call kthread_stop() after that, the "should stop" request won't be noticed until run_workqueue() returns. Signed-off-by: Oleg Nesterov Cc: Michal Schmidt Cc: Srivatsa Vaddagiri Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Freezer: make kernel threads nonfreezable by default

2007-07-17T17:23:02Z

Currently, the freezer treats all tasks as freezable, except for the kernel threads that explicitly set the PF_NOFREEZE flag for themselves. This approach is problematic, since it requires every kernel thread to either set PF_NOFREEZE explicitly, or call try_to_freeze(), even if it doesn't care for the freezing of tasks at all. It seems better to only require the kernel threads that want to or need to be frozen to use some freezer-related code and to remove any freezer-related code from the other (nonfreezable) kernel threads, which is done in this patch. The patch causes all kernel threads to be nonfreezable by default (ie. to have PF_NOFREEZE set by default) and introduces the set_freezable() function that should be called by the freezable kernel threads in order to unset PF_NOFREEZE. It also makes all of the currently freezable kernel threads call set_freezable(), so it shouldn't cause any (intentional) change of behaviour to appear. Additionally, it updates documentation to describe the freezing of tasks more accurately. [akpm@linux-foundation.org: build fixes] Signed-off-by: Rafael J. Wysocki Acked-by: Nigel Cunningham Cc: Pavel Machek Cc: Oleg Nesterov Cc: Gautham R Shenoy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

make cancel_xxx_work_sync() return a boolean

2007-07-16T16:05:51Z

Change cancel_work_sync() and cancel_delayed_work_sync() to return a boolean indicating whether the work was actually cancelled. A zero return value means that the work was not pending/queued. Without that kind of change it is not possible to avoid flush_workqueue() sometimes, see the next patch as an example. Also, this patch unifies both functions and kills the (unlikely) busy-wait loop. Signed-off-by: Oleg Nesterov Acked-by: Jarek Poplawski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

rename cancel_rearming_delayed_work() to cancel_delayed_work_sync()

2007-07-16T16:05:51Z

Imho, the current naming of cancel_xxx workqueue functions is very confusing. cancel_delayed_work() cancel_rearming_delayed_work() cancel_rearming_delayed_workqueue() // obsolete cancel_work_sync() This looks as if the first 2 functions differ in "type" of their argument which is not true any longer, nowadays the difference is the behaviour. The semantics of cancel_rearming_delayed_work(dwork) was changed significantly, it doesn't require that dwork rearms itself, and cancels dwork synchronously. Rename it to cancel_delayed_work_sync(). This matches cancel_delayed_work() and cancel_work_sync(). Re-create cancel_rearming_delayed_work() as a simple inline obsolete wrapper, like cancel_rearming_delayed_workqueue(). Signed-off-by: Oleg Nesterov Acked-by: Jarek Poplawski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

simplify cleanup_workqueue_thread()

2007-05-24T03:14:13Z

cleanup_workqueue_thread() and cwq_should_stop() are overcomplicated. Convert the code to use kthread_should_stop/kthread_stop as was suggested by Gautham and Srivatsa. In particular this patch removes the (unlikely) busy-wait loop from the exit path, it was a temporary and ugly kludge (if not a bug). Note: the current code was designed to solve another old problem: work->func can't share locks with hotplug callbacks. I think this could be done, see http://marc.info/?l=linux-kernel&m=116905366428633 but this needs some more complications to preserve CPU affinity of cwq->thread during cpu_up(). A freezer-based hotplug looks more appealing. [akpm@linux-foundation.org: make it more tolerant of gcc borkenness] Signed-off-by: Oleg Nesterov Cc: Zilvinas Valinskas Cc: Gautham R Shenoy Cc: Srivatsa Vaddagiri Cc: "Rafael J. Wysocki" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Add suspend-related notifications for CPU hotplug

2007-05-09T19:30:56Z

Since nonboot CPUs are now disabled after tasks and devices have been frozen and the CPU hotplug infrastructure is used for this purpose, we need special CPU hotplug notifications that will help the CPU-hotplug-aware subsystems distinguish normal CPU hotplug events from CPU hotplug events related to a system-wide suspend or resume operation in progress. This patch introduces such notifications and causes them to be used during suspend and resume transitions. It also changes all of the CPU-hotplug-aware subsystems to take these notifications into consideration (for now they are handled in the same way as the corresponding "normal" ones). [oleg@tv-sign.ru: cleanups] Signed-off-by: Rafael J. Wysocki Cc: Gautham R Shenoy Cc: Pavel Machek Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds