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signal: do_sigtimedwait() needs retarget_shared_pending()

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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>
This commit is contained in:
Oleg Nesterov 2011-04-27 21:56:14 +02:00
parent 943df1485a
commit b182801ab3
1 changed files with 17 additions and 12 deletions
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29
kernel/signal.c
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@ -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);