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recalc_sigpending_tsk fixes

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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 <roland@redhat.com>
Cc: <Steve.Hawkes@motorola.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2007-05-23 13:57:44 -07:00 • committed by Linus Torvalds
parent 3c6df2a917
commit 7bb44adef3
4 changed files with 28 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

24
kernel/signal.c
View file

@ -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);
}