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authorTejun Heo <tj@kernel.org>2011-06-02 11:14:00 +0200
committerOleg Nesterov <oleg@redhat.com>2011-06-04 18:17:11 +0200
commit6dfca32984237a8a011b5bf367e53341a265b2a4 (patch)
treea879c682f00921959ee28b563b9024c0ac54f861 /kernel/signal.c
parent3759a0d94c18764247b66511d1038f2b93aa95de (diff)
job control: make task_clear_jobctl_pending() clear TRAPPING automatically
JOBCTL_TRAPPING indicates that ptracer is waiting for tracee to (re)transit into TRACED. task_clear_jobctl_pending() must be called when either tracee enters TRACED or the transition is cancelled for some reason. The former is achieved by explicitly calling task_clear_jobctl_pending() in ptrace_stop() and the latter by calling it at the end of do_signal_stop(). Calling task_clear_jobctl_trapping() at the end of do_signal_stop() limits the scope TRAPPING can be used and is fragile in that seemingly unrelated changes to tracee's control flow can lead to stuck TRAPPING. We already have task_clear_jobctl_pending() calls on those cancelling events to clear JOBCTL_STOP_PENDING. Cancellations can be handled by making those call sites use JOBCTL_PENDING_MASK instead and updating task_clear_jobctl_pending() such that task_clear_jobctl_trapping() is called automatically if no stop/trap is pending. This patch makes the above changes and removes the fallback task_clear_jobctl_trapping() call from do_signal_stop(). Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'kernel/signal.c')
-rw-r--r--kernel/signal.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 288d952fa3b..637a171b65b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -253,6 +253,9 @@ static void task_clear_jobctl_trapping(struct task_struct *task)
* %JOBCTL_PENDING_MASK. If %JOBCTL_STOP_PENDING is being cleared, other
* STOP bits are cleared together.
*
+ * If clearing of @mask leaves no stop or trap pending, this function calls
+ * task_clear_jobctl_trapping().
+ *
* CONTEXT:
* Must be called with @task->sighand->siglock held.
*/
@@ -264,6 +267,9 @@ void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask)
mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED;
task->jobctl &= ~mask;
+
+ if (!(task->jobctl & JOBCTL_PENDING_MASK))
+ task_clear_jobctl_trapping(task);
}
/**
@@ -933,7 +939,7 @@ static void complete_signal(int sig, struct task_struct *p, int group)
signal->group_stop_count = 0;
t = p;
do {
- task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
+ task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
} while_each_thread(p, t);
@@ -1168,7 +1174,7 @@ int zap_other_threads(struct task_struct *p)
p->signal->group_stop_count = 0;
while_each_thread(p, t) {
- task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
+ task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
count++;
/* Don't bother with already dead threads */
@@ -1964,9 +1970,6 @@ retry:
goto retry;
}
- /* PTRACE_ATTACH might have raced with task killing, clear trapping */
- task_clear_jobctl_trapping(current);
-
spin_unlock_irq(&current->sighand->siglock);
tracehook_finish_jctl();