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signal: do_sigtimedwait() needs retarget_shared_pending()
do_sigtimedwait() changes current->blocked and thus it needs set_current_blocked()->retarget_shared_pending(). We could use set_current_blocked() 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> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>
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@ -2299,6 +2299,18 @@ long do_no_restart_syscall(struct restart_block *param)
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return -EINTR;
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}
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static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
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{
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if (signal_pending(tsk) && !thread_group_empty(tsk)) {
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sigset_t newblocked;
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/* A set of now blocked but previously unblocked signals. */
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signandsets(&newblocked, newset, ¤t->blocked);
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retarget_shared_pending(tsk, &newblocked);
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}
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tsk->blocked = *newset;
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recalc_sigpending();
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}
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/**
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* set_current_blocked - change current->blocked mask
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* @newset: new mask
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@ -2311,14 +2323,7 @@ void set_current_blocked(const sigset_t *newset)
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struct task_struct *tsk = current;
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spin_lock_irq(&tsk->sighand->siglock);
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if (signal_pending(tsk) && !thread_group_empty(tsk)) {
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sigset_t newblocked;
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/* A set of now blocked but previously unblocked signals. */
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signandsets(&newblocked, newset, ¤t->blocked);
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retarget_shared_pending(tsk, &newblocked);
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}
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tsk->blocked = *newset;
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recalc_sigpending();
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__set_task_blocked(tsk, newset);
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spin_unlock_irq(&tsk->sighand->siglock);
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}
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@ -2541,7 +2546,8 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
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/*
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* None ready, temporarily unblock those we're interested
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* while we are sleeping in so that we'll be awakened when
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* they arrive.
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* they arrive. Unblocking is always fine, we can avoid
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* set_current_blocked().
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*/
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tsk->real_blocked = tsk->blocked;
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sigandsets(&tsk->blocked, &tsk->blocked, &mask);
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@ -2551,10 +2557,9 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
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timeout = schedule_timeout_interruptible(timeout);
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spin_lock_irq(&tsk->sighand->siglock);
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sig = dequeue_signal(tsk, &mask, info);
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tsk->blocked = tsk->real_blocked;
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__set_task_blocked(tsk, &tsk->real_blocked);
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siginitset(&tsk->real_blocked, 0);
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recalc_sigpending();
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sig = dequeue_signal(tsk, &mask, info);
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}
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spin_unlock_irq(&tsk->sighand->siglock);
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