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authorOleg Nesterov <oleg@tv-sign.ru>2007-08-22 14:01:58 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-08-22 19:52:47 -0700
commitabd96ecb298675a21c412a29f5de2f80174d5f18 (patch)
tree5fb722fcfc224bf3e69a06a9e87d8fe56e1a6548
parent5c076fce2e217240b44bc753a5ec8ecd379c6eb9 (diff)
exec: kill unsafe BUG_ON(sig->count) checks
de_thread: if (atomic_read(&oldsighand->count) <= 1) BUG_ON(atomic_read(&sig->count) != 1); This is not safe without the rmb() in between. The results of two correctly ordered __exit_signal()->atomic_dec_and_test()'s could be seen out of order on our CPU. The same is true for the "thread_group_empty()" case, __unhash_process()'s changes could be seen before atomic_dec_and_test(&sig->count). On some platforms (including i386) atomic_read() doesn't provide even the compiler barrier, in that case these checks are simply racy. Remove these BUG_ON()'s. Alternatively, we can do something like BUG_ON( ({ smp_rmb(); atomic_read(&sig->count) != 1; }) ); Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/exec.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/fs/exec.c b/fs/exec.c
index af4361c927a..c21a8cc0627 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -784,7 +784,6 @@ static int de_thread(struct task_struct *tsk)
* and we can just re-use it all.
*/
if (atomic_read(&oldsighand->count) <= 1) {
- BUG_ON(atomic_read(&sig->count) != 1);
signalfd_detach(tsk);
exit_itimers(sig);
return 0;
@@ -929,8 +928,6 @@ no_thread_group:
if (leader)
release_task(leader);
- BUG_ON(atomic_read(&sig->count) != 1);
-
if (atomic_read(&oldsighand->count) == 1) {
/*
* Now that we nuked the rest of the thread group,