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| author | Oleg Nesterov <oleg@tv-sign.ru> | 2007-08-22 14:01:58 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-08-22 19:52:47 -0700 |
| commit | abd96ecb298675a21c412a29f5de2f80174d5f18 (patch) | |
| tree | 5fb722fcfc224bf3e69a06a9e87d8fe56e1a6548 /fs | |
| parent | 5c076fce2e217240b44bc753a5ec8ecd379c6eb9 (diff) | |
| download | blackbird-op-linux-abd96ecb298675a21c412a29f5de2f80174d5f18.tar.gz blackbird-op-linux-abd96ecb298675a21c412a29f5de2f80174d5f18.zip | |
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>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/exec.c | 3 |
1 files changed, 0 insertions, 3 deletions
diff --git a/fs/exec.c b/fs/exec.c index af4361c927a9..c21a8cc06277 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, |
