Commit b182801a authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarMatt Fleming <matt.fleming@linux.intel.com>
parent 943df148

kernel/signal.c

+17 −12
Original line number Diff line number Diff line
@@ -2299,6 +2299,18 @@ long do_no_restart_syscall(struct restart_block *param) 
	return -EINTR;

}



static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)

{

	if (signal_pending(tsk) && !thread_group_empty(tsk)) {

		sigset_t newblocked;

		/* A set of now blocked but previously unblocked signals. */

		signandsets(&newblocked, newset, &current->blocked);

		retarget_shared_pending(tsk, &newblocked);

	}

	tsk->blocked = *newset;

	recalc_sigpending();

}



/**

 * set_current_blocked - change current->blocked mask

 * @newset: new mask
@@ -2311,14 +2323,7 @@ void set_current_blocked(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;

		/* A set of now blocked but previously unblocked signals. */

		signandsets(&newblocked, newset, &current->blocked);

		retarget_shared_pending(tsk, &newblocked);

	}

	tsk->blocked = *newset;

	recalc_sigpending();

	__set_task_blocked(tsk, newset);

	spin_unlock_irq(&tsk->sighand->siglock);

}
@@ -2541,7 +2546,8 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info, 
		/*

		 * None ready, temporarily unblock those we're interested

		 * while we are sleeping in so that we'll be awakened when

		 * they arrive.

		 * they arrive. Unblocking is always fine, we can avoid

		 * set_current_blocked().

		 */

		tsk->real_blocked = tsk->blocked;

		sigandsets(&tsk->blocked, &tsk->blocked, &mask);
@@ -2551,10 +2557,9 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info, 
		timeout = schedule_timeout_interruptible(timeout);



		spin_lock_irq(&tsk->sighand->siglock);

		sig = dequeue_signal(tsk, &mask, info);

		tsk->blocked = tsk->real_blocked;

		__set_task_blocked(tsk, &tsk->real_blocked);

		siginitset(&tsk->real_blocked, 0);

		recalc_sigpending();

		sig = dequeue_signal(tsk, &mask, info);

	}

	spin_unlock_irq(&tsk->sighand->siglock);

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