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-rw-r--r--kernel/signal.c23
1 files changed, 20 insertions, 3 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 1e199919ae09..2f2c8f6ee01f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1827,10 +1827,27 @@ static int do_signal_stop(int signr)
unlikely(signal_group_exit(sig)))
return 0;
/*
- * There is no group stop already in progress.
- * We must initiate one now.
+ * There is no group stop already in progress. We must
+ * initiate one now.
+ *
+ * While ptraced, a task may be resumed while group stop is
+ * still in effect and then receive a stop signal and
+ * initiate another group stop. This deviates from the
+ * usual behavior as two consecutive stop signals can't
+ * cause two group stops when !ptraced.
+ *
+ * The condition can be distinguished by testing whether
+ * SIGNAL_STOP_STOPPED is already set. Don't generate
+ * group_exit_code in such case.
+ *
+ * This is not necessary for SIGNAL_STOP_CONTINUED because
+ * an intervening stop signal is required to cause two
+ * continued events regardless of ptrace.
*/
- sig->group_exit_code = signr;
+ if (!(sig->flags & SIGNAL_STOP_STOPPED))
+ sig->group_exit_code = signr;
+ else
+ WARN_ON_ONCE(!task_ptrace(current));
current->group_stop &= ~GROUP_STOP_SIGMASK;
current->group_stop |= signr | gstop;
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