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authorSrivatsa Vaddagiri <vatsa@in.ibm.com>2007-05-08 00:27:25 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 11:15:05 -0700
commitdd9037a26a1e6ebec9121b4681c414dc77189a90 (patch)
treecbce9dc3406943b0026a5de01bd64d42714a9413 /kernel
parente5f00f42f35e6f4699f105a3bd56874847cbf72f (diff)
downloadlwn-dd9037a26a1e6ebec9121b4681c414dc77189a90.tar.gz
lwn-dd9037a26a1e6ebec9121b4681c414dc77189a90.zip
Fix race between attach_task and cpuset_exit
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cpuset.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index d240349cbf0f..bde714db2b26 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -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;