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 <[email protected]>
--- t/fs/exec.c~1_BUG_ON 2007-08-18 17:36:58.000000000 +0400
+++ t/fs/exec.c 2007-08-18 18:19:41.000000000 +0400
@@ -784,7 +784,6 @@ static int de_thread(struct task_struct
* 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,
-
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