tracehook: force signal_pending()

This defines a new hook tracehook_force_sigpending() that lets tracing
code decide to force TIF_SIGPENDING on in recalc_sigpending().

This is not used yet, so it compiles away to nothing for now.  It lays the
groundwork for new tracing code that can interrupt a task synthetically
without actually sending a signal.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 0e862d3130ff..954f77d7e3bc 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -134,7 +134,9 @@ void recalc_sigpending_and_wake(struct task_struct *t)
 
 void recalc_sigpending(void)
 {
-        if (!recalc_sigpending_tsk(current) && !freezing(current))
+        if (unlikely(tracehook_force_sigpending()))
+                set_thread_flag(TIF_SIGPENDING);
+        else if (!recalc_sigpending_tsk(current) && !freezing(current))
                 clear_thread_flag(TIF_SIGPENDING);
 
 }