freezer: do not send signals to kernel threads

The freezer should not send signals to kernel threads, since that may lead to
subtle problems.  In particular, commit
b74d0deb968e1f85942f17080eace015ce3c332c has changed recalc_sigpending_tsk()
so that it doesn't clear TIF_SIGPENDING.  For this reason, if the freezer
continues to send fake signals to kernel threads and the freezing of kernel
threads fails, some of them may be running with TIF_SIGPENDING set forever.

Accordingly, recalc_sigpending_tsk() shouldn't set the task's TIF_SIGPENDING
flag if TIF_FREEZE is set.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 1 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 2124ffadcfd..e4f059cd986 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -99,7 +99,6 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
 static int recalc_sigpending_tsk(struct task_struct *t)
 {
         if (t->signal->group_stop_count > 0 ||
-            (freezing(t)) ||
             PENDING(&t->pending, &t->blocked) ||
             PENDING(&t->signal->shared_pending, &t->blocked)) {
                 set_tsk_thread_flag(t, TIF_SIGPENDING);