linux/kernel/workqueue.c, branch v2.6.38

workqueue: make sure MAYDAY_INITIAL_TIMEOUT is at least 2 jiffies long

2011-02-16T17:10:19Z

MAYDAY_INITIAL_TIMEOUT is defined as HZ / 100 and depending on configuration may end up 0 or 1. Even when it's 1, depending on when the mayday timer is added in the current jiffy interval, it may expire way before a jiffy has passed. Make sure MAYDAY_INITIAL_TIMEOUT is at least two to guarantee that at least a full jiffy has passed before calling rescuers. Signed-off-by: Tejun Heo Reported-by: Ray Jui Cc: stable@kernel.org

workqueue, freezer: unify spelling of 'freeze' + 'able' to 'freezable'

2011-02-16T16:48:59Z

There are two spellings in use for 'freeze' + 'able' - 'freezable' and 'freezeable'. The former is the more prominent one. The latter is mostly used by workqueue and in a few other odd places. Unify the spelling to 'freezable'. Signed-off-by: Tejun Heo Reported-by: Alan Stern Acked-by: "Rafael J. Wysocki" Acked-by: Greg Kroah-Hartman Acked-by: Dmitry Torokhov Cc: David Woodhouse Cc: Alex Dubov Cc: "David S. Miller" Cc: Steven Whitehouse

workqueue: wake up a worker when a rescuer is leaving a gcwq

2011-02-14T13:04:46Z

After executing the matching works, a rescuer leaves the gcwq whether there are more pending works or not. This may decrease the concurrency level to zero and stall execution until a new work item is queued on the gcwq. Make rescuer wake up a regular worker when it leaves a gcwq if there are more works to execute, so that execution isn't stalled. Signed-off-by: Tejun Heo Reported-by: Ray Jui Cc: stable@kernel.org

workqueue: note the nested NOT_RUNNING test in worker_clr_flags() isn't a noop

2011-01-11T15:03:14Z

The nested NOT_RUNNING test in worker_clr_flags() is slightly misleading in that if NOT_RUNNING were a single flag the nested test would be always %true and thus noop. Add a comment noting that the test isn't a noop. Signed-off-by: Tejun Heo Cc: Hillf Danton Cc: Andrew Morton

workqueue: relax lockdep annotation on flush_work()

2011-01-11T14:33:01Z

Currently, the lockdep annotation in flush_work() requires exclusive access on the workqueue the target work is queued on and triggers warning if a work is trying to flush another work on the same workqueue; however, this is no longer true as workqueues can now execute multiple works concurrently. This patch adds lock_map_acquire_read() and make process_one_work() hold read access to the workqueue while executing a work and start_flush_work() check for write access if concurrnecy level is one or the workqueue has a rescuer (as only one execution resource - the rescuer - is guaranteed to be available under memory pressure), and read access if higher. This better represents what's going on and removes spurious lockdep warnings which are triggered by fake dependency chain created through flush_work(). * Peter pointed out that flushing another work from a WQ_MEM_RECLAIM wq breaks forward progress guarantee under memory pressure. Condition check accordingly updated. Signed-off-by: Tejun Heo Reported-by: "Rafael J. Wysocki" Tested-by: "Rafael J. Wysocki" Cc: Peter Zijlstra Cc: stable@kernel.org

workqueue: allow chained queueing during destruction

2010-12-20T18:32:04Z

Currently, destroy_workqueue() makes the workqueue deny all new queueing by setting WQ_DYING and flushes the workqueue once before proceeding with destruction; however, there are cases where work items queue more related work items. Currently, such users need to explicitly flush the workqueue multiple times depending on the possible depth of such chained queueing. This patch updates the queueing path such that a work item can queue further work items on the same workqueue even when WQ_DYING is set. The flush on destruction is automatically retried until the workqueue is empty. This guarantees that the workqueue is empty on destruction while allowing chained queueing. The flush retry logic whines if it takes too many retries to drain the workqueue. Signed-off-by: Tejun Heo Cc: James Bottomley

workqueue: It is likely that WORKER_NOT_RUNNING is true

2010-12-14T14:05:54Z

Running the annotate branch profiler on three boxes, including my main box that runs firefox, evolution, xchat, and is part of the distcc farm, showed this with the likelys in the workqueue code: correct incorrect % Function File Line ------- --------- - -------- ---- ---- 96 996253 99 wq_worker_sleeping workqueue.c 703 96 996247 99 wq_worker_waking_up workqueue.c 677 The likely()s in this case were assuming that WORKER_NOT_RUNNING will most likely be false. But this is not the case. The reason is (and shown by adding trace_printks and testing it) that most of the time WORKER_PREP is set. In worker_thread() we have: worker_clr_flags(worker, WORKER_PREP); [ do work stuff ] worker_set_flags(worker, WORKER_PREP, false); (that 'false' means not to wake up an idle worker) The wq_worker_sleeping() is called from schedule when a worker thread is putting itself to sleep. Which happens most of the time outside of that [ do work stuff ]. The wq_worker_waking_up is called by the wakeup worker code, which is also callod outside that [ do work stuff ]. Thus, the likely and unlikely used by those two functions are actually backwards. Remove the annotation and let gcc figure it out. Acked-by: Tejun Heo Signed-off-by: Steven Rostedt Signed-off-by: Tejun Heo

workqueue: check the allocation of system_unbound_wq

2010-11-26T11:06:44Z

I found a trivial bug on initialization of workqueue. Current init_workqueues doesn't check the result of allocation of system_unbound_wq, this should be checked like other queues. Signed-off-by: Hitoshi Mitake Cc: Arjan van de Ven Cc: David Howells Signed-off-by: Tejun Heo

workqueues: s/ON_STACK/ONSTACK/

2010-10-26T23:52:14Z

Silly though it is, completions and wait_queue_heads use foo_ONSTACK (COMPLETION_INITIALIZER_ONSTACK, DECLARE_COMPLETION_ONSTACK, __WAIT_QUEUE_HEAD_INIT_ONSTACK and DECLARE_WAIT_QUEUE_HEAD_ONSTACK) so I guess workqueues should do the same thing. s/INIT_WORK_ON_STACK/INIT_WORK_ONSTACK/ s/INIT_DELAYED_WORK_ON_STACK/INIT_DELAYED_WORK_ONSTACK/ Cc: Peter Zijlstra Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

MN10300: Fix the PERCPU() alignment to allow for workqueues

2010-10-25T23:24:06Z

In the MN10300 arch, we occasionally see an assertion being tripped in alloc_cwqs() at the following line: /* just in case, make sure it's actually aligned */ ---> BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align)); return wq->cpu_wq.v ? 0 : -ENOMEM; The values are: wa->cpu_wq.v => 0x902776e0 align => 0x100 and align is calculated by the following: const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS, __alignof__(unsigned long long)); This is because the pointer in question (wq->cpu_wq.v) loses some of its lower bits to control flags, and so the object it points to must be sufficiently aligned to avoid the need to use those bits for pointing to things. Currently, 4 control bits and 4 colour bits are used in normal circumstances, plus a debugging bit if debugging is set. This requires the cpu_workqueue_struct struct to be at least 256 bytes aligned (or 512 bytes aligned with debugging). PERCPU() alignment on MN13000, however, is only 32 bytes as set in vmlinux.lds.S. So we set this to PAGE_SIZE (4096) to match most other arches and stick a comment in alloc_cwqs() for anyone else who triggers the assertion. Reported-by: Akira Takeuchi Signed-off-by: David Howells Acked-by: Mark Salter Cc: Tejun Heo Signed-off-by: Linus Torvalds