From 7bb44adef39ad3bda2be40bb34686bc56bd563a5 Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Wed, 23 May 2007 13:57:44 -0700 Subject: recalc_sigpending_tsk fixes Steve Hawkes discovered a problem where recalc_sigpending_tsk was called in do_sigaction but no signal_wake_up call was made, preventing later signals from waking up blocked threads with TIF_SIGPENDING already set. In fact, the few other calls to recalc_sigpending_tsk outside the signals code are also subject to this problem in other race conditions. This change makes recalc_sigpending_tsk private to the signals code. It changes the outside calls, as well as do_sigaction, to use the new recalc_sigpending_and_wake instead. Signed-off-by: Roland McGrath Cc: Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 364fc95bf97c..acdfc0549c6f 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -96,15 +96,27 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked) #define PENDING(p,b) has_pending_signals(&(p)->signal, (b)) -fastcall void recalc_sigpending_tsk(struct task_struct *t) +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)) + PENDING(&t->signal->shared_pending, &t->blocked)) { set_tsk_thread_flag(t, TIF_SIGPENDING); - else - clear_tsk_thread_flag(t, TIF_SIGPENDING); + return 1; + } + clear_tsk_thread_flag(t, TIF_SIGPENDING); + return 0; +} + +/* + * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up. + * This is superfluous when called on current, the wakeup is a harmless no-op. + */ +void recalc_sigpending_and_wake(struct task_struct *t) +{ + if (recalc_sigpending_tsk(t)) + signal_wake_up(t, 0); } void recalc_sigpending(void) @@ -744,7 +756,7 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t) action->sa.sa_handler = SIG_DFL; if (blocked) { sigdelset(&t->blocked, sig); - recalc_sigpending_tsk(t); + recalc_sigpending_and_wake(t); } } ret = specific_send_sig_info(sig, info, t); @@ -2273,7 +2285,7 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) rm_from_queue_full(&mask, &t->signal->shared_pending); do { rm_from_queue_full(&mask, &t->pending); - recalc_sigpending_tsk(t); + recalc_sigpending_and_wake(t); t = next_thread(t); } while (t != current); } -- cgit v1.2.3