handle_stop_signal: unify partial/full stop handling

Now that handle_stop_signal() doesn't drop ->siglock, we can't see both
->group_stop_count && SIGNAL_STOP_STOPPED.  Merge two "if" branches.

As Roland pointed out, we never actually needed 2 do_notify_parent_cldstop()
calls.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/signal.c b/kernel/signal.c
index ce53ab19c21d99f1ae37c13d6b66b8ac98cca6c9..dee8cc927a63635b61003902dc013deb02d955d6 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -585,33 +585,16 @@ static void handle_stop_signal(int sig, struct task_struct *p)
                        t = next_thread(t);
                } while (t != p);
        } else if (sig == SIGCONT) {
+               unsigned int why;
                /*
                 * Remove all stop signals from all queues,
                 * and wake all threads.
                 */
-               if (unlikely(p->signal->group_stop_count > 0)) {
-                       /*
-                        * There was a group stop in progress.  We'll
-                        * pretend it finished before we got here.  We are
-                        * obliged to report it to the parent: if the
-                        * SIGSTOP happened "after" this SIGCONT, then it
-                        * would have cleared this pending SIGCONT.  If it
-                        * happened "before" this SIGCONT, then the parent
-                        * got the SIGCHLD about the stop finishing before
-                        * the continue happened.  We do the notification
-                        * now, and it's as if the stop had finished and
-                        * the SIGCHLD was pending on entry to this kill.
-                        */
-                       p->signal->group_stop_count = 0;
-                       p->signal->flags = SIGNAL_STOP_CONTINUED |
-                                               SIGNAL_CLD_STOPPED;
-               }
                rm_from_queue(SIG_KERNEL_STOP_MASK, &p->signal->shared_pending);
                t = p;
                do {
                        unsigned int state;
                        rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
-                       
                        /*
                         * If there is a handler for SIGCONT, we must make
                         * sure that no thread returns to user mode before
@@ -621,7 +604,7 @@ static void handle_stop_signal(int sig, struct task_struct *p)
                         * running the handler.  With the TIF_SIGPENDING
                         * flag set, the thread will pause and acquire the
                         * siglock that we hold now and until we've queued
-                        * the pending signal. 
+                        * the pending signal.
                         *
                         * Wake up the stopped thread _after_ setting
                         * TIF_SIGPENDING
@@ -636,13 +619,23 @@ static void handle_stop_signal(int sig, struct task_struct *p)
                        t = next_thread(t);
                } while (t != p);
 
-               if (p->signal->flags & SIGNAL_STOP_STOPPED) {
-                       /*
-                        * We were in fact stopped, and are now continued.
-                        * Notify the parent with CLD_CONTINUED.
-                        */
-                       p->signal->flags = SIGNAL_STOP_CONTINUED |
-                                               SIGNAL_CLD_CONTINUED;
+               /*
+                * Notify the parent with CLD_CONTINUED if we were stopped.
+                *
+                * If we were in the middle of a group stop, we pretend it
+                * was already finished, and then continued. Since SIGCHLD
+                * doesn't queue we report only CLD_STOPPED, as if the next
+                * CLD_CONTINUED was dropped.
+                */
+               why = 0;
+               if (p->signal->flags & SIGNAL_STOP_STOPPED)
+                       why |= SIGNAL_CLD_CONTINUED;
+               else if (p->signal->group_stop_count)
+                       why |= SIGNAL_CLD_STOPPED;
+
+               if (why) {
+                       p->signal->flags = why | SIGNAL_STOP_CONTINUED;
+                       p->signal->group_stop_count = 0;
                        p->signal->group_exit_code = 0;
                } else {
                        /*