From 5b0f437df0a3e374d26ad533eb78fe64744f55a8 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Thu, 30 Jul 2009 19:00:53 +0200 Subject: workqueues: Improve schedule_work() documentation Two important aspects of the schedule_work() function are not yet documented: - that it is allowed to pass a struct work_struct * to this function that is already on the kernel-global workqueue; - the meaning of its return value. The patch below documents both aspects. Signed-off-by: Bart Van Assche Cc: "Greg Kroah-Hartman" Cc: Andrew Morton LKML-Reference: <200907301900.54202.bart.vanassche@gmail.com> Signed-off-by: Ingo Molnar --- kernel/workqueue.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'kernel/workqueue.c') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 0668795d8818..3c44b56b0da7 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -600,7 +600,12 @@ static struct workqueue_struct *keventd_wq __read_mostly; * schedule_work - put work task in global workqueue * @work: job to be done * - * This puts a job in the kernel-global workqueue. + * Returns zero if @work was already on the kernel-global workqueue and + * non-zero otherwise. + * + * This puts a job in the kernel-global workqueue if it was not already + * queued and leaves it in the same position on the kernel-global + * workqueue otherwise. */ int schedule_work(struct work_struct *work) { -- cgit v1.3-14-g43fede From 61cbe54d9479ad98283b2dda686deae4c34b2d59 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Wed, 9 Sep 2009 15:41:37 +0200 Subject: sched: Keep kthreads at default priority Removes kthread/workqueue priority boost, they increase worst-case desktop latencies. Signed-off-by: Mike Galbraith Acked-by: Peter Zijlstra LKML-Reference: <1252486344.28645.18.camel@marge.simson.net> Signed-off-by: Ingo Molnar --- kernel/kthread.c | 4 ---- kernel/workqueue.c | 2 -- 2 files changed, 6 deletions(-) (limited to 'kernel/workqueue.c') diff --git a/kernel/kthread.c b/kernel/kthread.c index eb8751aa0418..5fe709982caa 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -16,8 +16,6 @@ #include #include -#define KTHREAD_NICE_LEVEL (-5) - static DEFINE_SPINLOCK(kthread_create_lock); static LIST_HEAD(kthread_create_list); struct task_struct *kthreadd_task; @@ -145,7 +143,6 @@ struct task_struct *kthread_create(int (*threadfn)(void *data), * The kernel thread should not inherit these properties. */ sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m); - set_user_nice(create.result, KTHREAD_NICE_LEVEL); set_cpus_allowed_ptr(create.result, cpu_all_mask); } return create.result; @@ -221,7 +218,6 @@ int kthreadd(void *unused) /* Setup a clean context for our children to inherit. */ set_task_comm(tsk, "kthreadd"); ignore_signals(tsk); - set_user_nice(tsk, KTHREAD_NICE_LEVEL); set_cpus_allowed_ptr(tsk, cpu_all_mask); set_mems_allowed(node_possible_map); diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 0668795d8818..ea1b4e7674d5 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -317,8 +317,6 @@ static int worker_thread(void *__cwq) if (cwq->wq->freezeable) set_freezable(); - set_user_nice(current, -5); - for (;;) { prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE); if (!freezing(current) && -- cgit v1.3-14-g43fede From 8c53e46314562fe814b0afef6cfcbd2f562b017c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 14 Oct 2009 09:16:42 -0700 Subject: workqueue: add 'flush_delayed_work()' to run and wait for delayed work It basically turns a delayed work into an immediate work, and then waits for it to finish, thus allowing you to force (and wait for) an immediate flush of a delayed work. We'll want to use this in the tty layer to clean up tty_flush_to_ldisc(). Acked-by: Oleg Nesterov [ Fixed to use 'del_timer_sync()' as noted by Oleg ] Signed-off-by: Linus Torvalds --- include/linux/workqueue.h | 1 + kernel/workqueue.c | 18 ++++++++++++++++++ 2 files changed, 19 insertions(+) (limited to 'kernel/workqueue.c') diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 7ef0c7b94f31..cf24c20de9e4 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -207,6 +207,7 @@ extern int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, extern void flush_workqueue(struct workqueue_struct *wq); extern void flush_scheduled_work(void); +extern void flush_delayed_work(struct delayed_work *work); extern int schedule_work(struct work_struct *work); extern int schedule_work_on(int cpu, struct work_struct *work); diff --git a/kernel/workqueue.c b/kernel/workqueue.c index addfe2df93b1..47cdd7e76f2b 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -639,6 +639,24 @@ int schedule_delayed_work(struct delayed_work *dwork, } EXPORT_SYMBOL(schedule_delayed_work); +/** + * flush_delayed_work - block until a dwork_struct's callback has terminated + * @dwork: the delayed work which is to be flushed + * + * Any timeout is cancelled, and any pending work is run immediately. + */ +void flush_delayed_work(struct delayed_work *dwork) +{ + if (del_timer_sync(&dwork->timer)) { + struct cpu_workqueue_struct *cwq; + cwq = wq_per_cpu(keventd_wq, get_cpu()); + __queue_work(cwq, &dwork->work); + put_cpu(); + } + flush_work(&dwork->work); +} +EXPORT_SYMBOL(flush_delayed_work); + /** * schedule_delayed_work_on - queue work in global workqueue on CPU after delay * @cpu: cpu to use -- cgit v1.3-14-g43fede From 65a64464349883891e21e74af16c05d6e1eeb4e9 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 14 Oct 2009 06:22:47 +0200 Subject: HWPOISON: Allow schedule_on_each_cpu() from keventd Right now when calling schedule_on_each_cpu() from keventd there is a deadlock because it tries to schedule a work item on the current CPU too. This happens via lru_add_drain_all() in hwpoison. Just call the function for the current CPU in this case. This is actually faster too. Debugging with Fengguang Wu & Max Asbock Signed-off-by: Andi Kleen --- kernel/workqueue.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) (limited to 'kernel/workqueue.c') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index addfe2df93b1..f61a2fecf281 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -667,21 +667,38 @@ EXPORT_SYMBOL(schedule_delayed_work_on); int schedule_on_each_cpu(work_func_t func) { int cpu; + int orig = -1; struct work_struct *works; works = alloc_percpu(struct work_struct); if (!works) return -ENOMEM; + /* + * when running in keventd don't schedule a work item on itself. + * Can just call directly because the work queue is already bound. + * This also is faster. + * Make this a generic parameter for other workqueues? + */ + if (current_is_keventd()) { + orig = raw_smp_processor_id(); + INIT_WORK(per_cpu_ptr(works, orig), func); + func(per_cpu_ptr(works, orig)); + } + get_online_cpus(); for_each_online_cpu(cpu) { struct work_struct *work = per_cpu_ptr(works, cpu); + if (cpu == orig) + continue; INIT_WORK(work, func); schedule_work_on(cpu, work); } - for_each_online_cpu(cpu) - flush_work(per_cpu_ptr(works, cpu)); + for_each_online_cpu(cpu) { + if (cpu != orig) + flush_work(per_cpu_ptr(works, cpu)); + } put_online_cpus(); free_percpu(works); return 0; -- cgit v1.3-14-g43fede From 9398180097e359646d46083c3e079a54e20bee82 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 17 Nov 2009 14:06:20 -0800 Subject: workqueue: fix race condition in schedule_on_each_cpu() Commit 65a64464349883891e21e74af16c05d6e1eeb4e9 ("HWPOISON: Allow schedule_on_each_cpu() from keventd") which allows schedule_on_each_cpu() to be called from keventd added a race condition. schedule_on_each_cpu() may race with cpu hotplug and end up executing the function twice on a cpu. Fix it by moving direct execution into the section protected with get/put_online_cpus(). While at it, update code such that direct execution is done after works have been scheduled for all other cpus and drop unnecessary cpu != orig test from flush loop. Signed-off-by: Tejun Heo Cc: Andi Kleen Acked-by: Oleg Nesterov Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/workqueue.c | 28 +++++++++++++--------------- 1 file changed, 13 insertions(+), 15 deletions(-) (limited to 'kernel/workqueue.c') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 12328147132c..67e526b6ae81 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -692,31 +692,29 @@ int schedule_on_each_cpu(work_func_t func) if (!works) return -ENOMEM; + get_online_cpus(); + /* - * when running in keventd don't schedule a work item on itself. - * Can just call directly because the work queue is already bound. - * This also is faster. - * Make this a generic parameter for other workqueues? + * When running in keventd don't schedule a work item on + * itself. Can just call directly because the work queue is + * already bound. This also is faster. */ - if (current_is_keventd()) { + if (current_is_keventd()) orig = raw_smp_processor_id(); - INIT_WORK(per_cpu_ptr(works, orig), func); - func(per_cpu_ptr(works, orig)); - } - get_online_cpus(); for_each_online_cpu(cpu) { struct work_struct *work = per_cpu_ptr(works, cpu); - if (cpu == orig) - continue; INIT_WORK(work, func); - schedule_work_on(cpu, work); - } - for_each_online_cpu(cpu) { if (cpu != orig) - flush_work(per_cpu_ptr(works, cpu)); + schedule_work_on(cpu, work); } + if (orig >= 0) + func(per_cpu_ptr(works, orig)); + + for_each_online_cpu(cpu) + flush_work(per_cpu_ptr(works, cpu)); + put_online_cpus(); free_percpu(works); return 0; -- cgit v1.3-14-g43fede