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authorOleg Nesterov <oleg@redhat.com>2009-06-17 16:27:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-18 13:03:53 -0700
commitf95d39d10fe7d47336e65172f52bf64e0096f983 (patch)
tree14b469b68455968dfd707695083ece72287dfaab /kernel
parenta3f6dfb7295facb0505b5beca5a7ce48b0612379 (diff)
downloadlinux-2.6.34-ux500-f95d39d10fe7d47336e65172f52bf64e0096f983.tar.gz
do_wait: fix the theoretical race with stop/trace/cont
do_wait: current->state = TASK_INTERRUPTIBLE; read_lock(&tasklist_lock); ... search for the task to reap ... In theory, the ->state changing can leak into the critical section. Since the child can change its status under read_lock(tasklist) in parallel (finish_stop/ptrace_stop), we can miss the wakeup if __wake_up_parent() sees us in TASK_RUNNING state. Add the barrier. Also, use __set_current_state() to set TASK_RUNNING. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Roland McGrath <roland@redhat.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/exit.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index dd83c841910..7ef355dd3dc 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1581,7 +1581,7 @@ repeat:
(!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
goto notask;
- current->state = TASK_INTERRUPTIBLE;
+ set_current_state(TASK_INTERRUPTIBLE);
read_lock(&tasklist_lock);
tsk = current;
do {
@@ -1608,7 +1608,7 @@ notask:
}
}
end:
- current->state = TASK_RUNNING;
+ __set_current_state(TASK_RUNNING);
remove_wait_queue(&current->signal->wait_chldexit,&wait);
if (wo->wo_info) {
struct siginfo __user *infop = wo->wo_info;