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Commit 31ad9081 authored by Rusty Russell's avatar Rusty Russell Committed by Ingo Molnar
Browse files

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: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarMike Travis <travis@sgi.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c7f8562a

kernel/workqueue.c

+4 −10
Original line number Original line Diff line number Diff line
@@ -991,8 +991,8 @@ static void do_work_for_cpu(struct work_struct *w) 
 * @fn: the function to run

 * @fn: the function to run

 * @arg: the function arg

 * @arg: the function arg

 *

 *

 * This will return -EINVAL in the cpu is not online, or the return value

 * This will return the value @fn returns.

 * of @fn otherwise.

 * 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)

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);

	INIT_WORK(&wfc.work, do_work_for_cpu);

	wfc.fn = fn;

	wfc.fn = fn;

	wfc.arg = arg;

	wfc.arg = arg;

	get_online_cpus();

	if (unlikely(!cpu_online(cpu)))

		wfc.ret = -EINVAL;

	else {

	schedule_work_on(cpu, &wfc.work);

	schedule_work_on(cpu, &wfc.work);

	flush_work(&wfc.work);

	flush_work(&wfc.work);

	}

	put_online_cpus();





	return wfc.ret;

	return wfc.ret;

}

}