Messages in this thread Patch in this message | | | Date | Sat, 23 Apr 2011 20:00:00 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 3/3] signal: do_sigtimedwait() needs retarget_shared_pending() |
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do_sigtimedwait() changes current->blocked and thus it needs set_current_bloked()->retarget_shared_pending().
We could use set_current_bloked() directly. It is fine to change ->real_blocked from all-zeroes to ->blocked and vice versa lockless, but this is not immediately clear, looks racy, and needs a huge comment to explain why this is correct.
To keep the things simple this patch adds the new static helper, __set_task_blocked() which should be called with ->siglock held. This way we can change both ->real_blocked and ->blocked atomically under ->siglock as the current code does. This is more understandable.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> ---
kernel/signal.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-)
--- sigprocmask/kernel/signal.c~3_sigtimedwait_retarget 2011-04-22 20:57:06.000000000 +0200 +++ sigprocmask/kernel/signal.c 2011-04-22 21:49:11.000000000 +0200 @@ -2115,11 +2115,8 @@ long do_no_restart_syscall(struct restar return -EINTR; } -void set_current_blocked(const sigset_t *newset) +static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset) { - struct task_struct *tsk = current; - - spin_lock_irq(&tsk->sighand->siglock); if (signal_pending(tsk) && !thread_group_empty(tsk)) { sigset_t newblocked; signandsets(&newblocked, newset, ¤t->blocked); @@ -2127,6 +2124,14 @@ void set_current_blocked(const sigset_t } tsk->blocked = *newset; recalc_sigpending(); +} + +void set_current_blocked(const sigset_t *newset) +{ + struct task_struct *tsk = current; + + spin_lock_irq(&tsk->sighand->siglock); + __set_task_blocked(tsk, newset); spin_unlock_irq(&tsk->sighand->siglock); } @@ -2322,7 +2327,8 @@ int do_sigtimedwait(sigset_t *these, sig /* * None ready -- temporarily unblock those we're * interested while we are sleeping in so that we'll - * be awakened when they arrive. + * be awakened when they arrive. Unblocking is always + * fine, we can avoid set_current_blocked(). */ tsk->real_blocked = tsk->blocked; sigandsets(&tsk->blocked, &tsk->blocked, these); @@ -2332,10 +2338,9 @@ int do_sigtimedwait(sigset_t *these, sig timeout = schedule_timeout_interruptible(timeout); spin_lock_irq(&tsk->sighand->siglock); - sig = dequeue_signal(tsk, these, info); - tsk->blocked = tsk->real_blocked; + __set_task_blocked(tsk, &tsk->real_blocked); siginitset(&tsk->real_blocked, 0); - recalc_sigpending(); + sig = dequeue_signal(tsk, these, info); } spin_unlock_irq(&tsk->sighand->siglock);
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