From 31ad9081200c06ccc350625d41d1f8b2d1cef29f Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 16 Jan 2009 15:31:15 -0800 Subject: work_on_cpu: don't try to get_online_cpus() in work_on_cpu. Impact: remove potential circular lock dependency with cpu hotplug lock This has caused more problems than it solved, with a pile of cpu hotplug locking issues. Followup patches will get_online_cpus() in callers that need it, but if they don't do it they're no worse than before when they were using set_cpus_allowed without locking. Signed-off-by: Rusty Russell Signed-off-by: Mike Travis Signed-off-by: Ingo Molnar --- kernel/workqueue.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) (limited to 'kernel') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 2f445833ae37..a35afdbc0161 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -991,8 +991,8 @@ static void do_work_for_cpu(struct work_struct *w) * @fn: the function to run * @arg: the function arg * - * This will return -EINVAL in the cpu is not online, or the return value - * of @fn otherwise. + * This will return the value @fn returns. + * It is up to the caller to ensure that the cpu doesn't go offline. */ long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) { @@ -1001,14 +1001,8 @@ long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) INIT_WORK(&wfc.work, do_work_for_cpu); wfc.fn = fn; wfc.arg = arg; - get_online_cpus(); - if (unlikely(!cpu_online(cpu))) - wfc.ret = -EINVAL; - else { - schedule_work_on(cpu, &wfc.work); - flush_work(&wfc.work); - } - put_online_cpus(); + schedule_work_on(cpu, &wfc.work); + flush_work(&wfc.work); return wfc.ret; } -- cgit v1.2.3 From 8ccad40df8d314f786fdb06bdbedd4f43f3257cd Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 16 Jan 2009 15:31:15 -0800 Subject: work_on_cpu: Use our own workqueue. Impact: remove potential clashes with generic kevent workqueue Annoyingly, some places we want to use work_on_cpu are already in workqueues. As per Ingo's suggestion, we create a different workqueue for work_on_cpu. Signed-off-by: Rusty Russell Signed-off-by: Mike Travis Signed-off-by: Ingo Molnar --- kernel/workqueue.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index a35afdbc0161..1f0c509b40d3 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -971,6 +971,8 @@ undo: } #ifdef CONFIG_SMP +static struct workqueue_struct *work_on_cpu_wq __read_mostly; + struct work_for_cpu { struct work_struct work; long (*fn)(void *); @@ -1001,7 +1003,7 @@ long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) INIT_WORK(&wfc.work, do_work_for_cpu); wfc.fn = fn; wfc.arg = arg; - schedule_work_on(cpu, &wfc.work); + queue_work_on(cpu, work_on_cpu_wq, &wfc.work); flush_work(&wfc.work); return wfc.ret; @@ -1019,4 +1021,8 @@ void __init init_workqueues(void) hotcpu_notifier(workqueue_cpu_callback, 0); keventd_wq = create_workqueue("events"); BUG_ON(!keventd_wq); +#ifdef CONFIG_SMP + work_on_cpu_wq = create_workqueue("work_on_cpu"); + BUG_ON(!work_on_cpu_wq); +#endif } -- cgit v1.2.3