lkml.org 
[lkml]   [2011]   [Dec]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [BUG] TASK_DEAD task is able to be woken up in special condition
On 12/26, Yasunori Goto wrote:
>
> >
> > IIRC, this was already discussed a bit. Say, try_to_wake_up(TASK_INTERRUPTIBLE)
> > can wakeup a TASK_UNINTERRUPTIBLE task if it temporary sets INTERRUPTIBLE but
> > doesn't call schedule() in this state.
>
> Oleg-san,
>
> Could you point the discussion?
> I don't understand yet how it occurred...

Suppose that the task T does

set_current_state(TASK_INTERRUPTIBLE);

set_current_state(TASK_UNINTERRUPTIBLE);
schedule();

try_to_wake_up(TASK_UNINTERRUPTIBLE) in between can observe this task
in TASK_INTERRUPTIBLE state. Then it can set RUNNING/WAKING after T
sets ->state = TASK_UNINTERRUPTIBLE.

For example, this is possibly if T simply does wait_event() twice when
the the 1st wait_event() doesn't sleep.

Basically this is the same race you described, but I think you found
the case when we can't tolerate the spurious wakeup.

Oleg.



\
 
 \ /
  Last update: 2011-12-26 18:19    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site