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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 <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Rusty Russell 2009-01-16 15:31:15 -08:00 committed by Ingo Molnar
parent c7f8562a51
commit 31ad908120
1 changed files with 4 additions and 10 deletions
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14
kernel/workqueue.c
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@ -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;
}