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Fix race between attach_task and cpuset_exit

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Currently cpuset_exit() changes the exiting task's ->cpuset pointer w/o
taking task_lock().  This can lead to ugly races between attach_task and
cpuset_exit.  Details of the races are described at
http://lkml.org/lkml/2007/3/24/132.

Patch below closes those races.

Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Srivatsa Vaddagiri 2007-05-08 00:27:25 -07:00 committed by Linus Torvalds
parent e5f00f42f3
commit dd9037a26a
1 changed files with 2 additions and 4 deletions
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6
kernel/cpuset.c
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@ -2200,10 +2200,6 @@ void cpuset_fork(struct task_struct *child)
* it is holding that mutex while calling check_for_release(),
* which calls kmalloc(), so can't be called holding callback_mutex().
*
* We don't need to task_lock() this reference to tsk->cpuset,
* because tsk is already marked PF_EXITING, so attach_task() won't
* mess with it, or task is a failed fork, never visible to attach_task.
*
* the_top_cpuset_hack:
*
* Set the exiting tasks cpuset to the root cpuset (top_cpuset).
@ -2242,8 +2238,10 @@ void cpuset_exit(struct task_struct *tsk)
{
struct cpuset *cs;
task_lock(current);
cs = tsk->cpuset;
tsk->cpuset = &top_cpuset; /* the_top_cpuset_hack - see above */
task_unlock(current);
if (notify_on_release(cs)) {
char *pathbuf = NULL;