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authorOleg Nesterov <oleg@tv-sign.ru>2007-10-16 23:27:23 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-17 08:42:54 -0700
commit6db840fa7887980ef68a649640d506fe069eef0c (patch)
tree6248c1e65b572f1c2b14c46848e5a18df003f60e /kernel
parent356d6d5058c8082b9e811838ab2fa27825c947e4 (diff)
exec: RT sub-thread can livelock and monopolize CPU on exec
de_thread() yields waiting for ->group_leader to be a zombie. This deadlocks if an rt-prio execer shares the same cpu with ->group_leader. Change the code to use ->group_exit_task/notify_count mechanics. This patch certainly uglifies the code, perhaps someone can suggest something better. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> 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 'kernel')
-rw-r--r--kernel/exit.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 25f6805be5f..4c108df88a3 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -92,10 +92,9 @@ static void __exit_signal(struct task_struct *tsk)
* If there is any task waiting for the group exit
* then notify it:
*/
- if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
+ if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
wake_up_process(sig->group_exit_task);
- sig->group_exit_task = NULL;
- }
+
if (tsk == sig->curr_target)
sig->curr_target = next_thread(tsk);
/*
@@ -827,6 +826,11 @@ static void exit_notify(struct task_struct *tsk)
state = EXIT_DEAD;
tsk->exit_state = state;
+ if (thread_group_leader(tsk) &&
+ tsk->signal->notify_count < 0 &&
+ tsk->signal->group_exit_task)
+ wake_up_process(tsk->signal->group_exit_task);
+
write_unlock_irq(&tasklist_lock);
list_for_each_safe(_p, _n, &ptrace_dead) {