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recalc_sigpending_tsk fixes

Browse source 
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
Show stats Download patch file Download diff file Expand all files Collapse all files

12
include/linux/sched.h
View file

@ -1616,11 +1616,13 @@ static inline int lock_need_resched(spinlock_t *lock)
return 0;
}
/* Reevaluate whether the task has signals pending delivery.
This is required every time the blocked sigset_t changes.
callers must hold sighand->siglock. */
extern FASTCALL(void recalc_sigpending_tsk(struct task_struct *t));
/*
* Reevaluate whether the task has signals pending delivery.
* Wake the task if so.
* This is required every time the blocked sigset_t changes.
* callers must hold sighand->siglock.
*/
extern void recalc_sigpending_and_wake(struct task_struct *t);
extern void recalc_sigpending(void);
extern void signal_wake_up(struct task_struct *t, int resume_stopped);

7
kernel/exit.c
View file

@ -762,11 +762,8 @@ static void exit_notify(struct task_struct *tsk)
read_lock(&tasklist_lock);
spin_lock_irq(&tsk->sighand->siglock);
for (t = next_thread(tsk); t != tsk; t = next_thread(t))
if (!signal_pending(t) && !(t->flags & PF_EXITING)) {
recalc_sigpending_tsk(t);
if (signal_pending(t))
signal_wake_up(t, 0);
}
if (!signal_pending(t) && !(t->flags & PF_EXITING))
recalc_sigpending_and_wake(t);
spin_unlock_irq(&tsk->sighand->siglock);
read_unlock(&tasklist_lock);
}

2
kernel/power/process.c
View file

@ -101,7 +101,7 @@ static void cancel_freezing(struct task_struct *p)
pr_debug(" clean up: %s\n", p->comm);
do_not_freeze(p);
spin_lock_irqsave(&p->sighand->siglock, flags);
recalc_sigpending_tsk(p);
recalc_sigpending_and_wake(p);
spin_unlock_irqrestore(&p->sighand->siglock, flags);
}
}

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);
}