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signal: sigprocmask: narrow the scope of ->siglock

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No functional changes, preparation to simplify the review of the next change.

1. We can read current->block lockless, nobody else can ever change this mask.

2. Calculate the resulting sigset_t outside of ->siglock into the temporary
   variable, then take ->siglock and change ->blocked.

Also, kill the stale comment about BKL.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Oleg Nesterov 2011-04-27 19:54:20 +02:00
parent fec9993db0
commit 73ef4aeb61
1 changed files with 14 additions and 17 deletions
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31
kernel/signal.c
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@ -2299,12 +2299,6 @@ long do_no_restart_syscall(struct restart_block *param)
return -EINTR;
}
/*
* We don't need to get the kernel lock - this is all local to this
* particular thread.. (and that's good, because this is _heavily_
* used by various programs)
*/
/*
* This is also useful for kernel threads that want to temporarily
* (or permanently) block certain signals.
@ -2315,30 +2309,33 @@ long do_no_restart_syscall(struct restart_block *param)
*/
int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
{
int error;
struct task_struct *tsk = current;
sigset_t newset;
spin_lock_irq(&current->sighand->siglock);
/* Lockless, only current can change ->blocked, never from irq */
if (oldset)
*oldset = current->blocked;
*oldset = tsk->blocked;
error = 0;
switch (how) {
case SIG_BLOCK:
sigorsets(&current->blocked, &current->blocked, set);
sigorsets(&newset, &tsk->blocked, set);
break;
case SIG_UNBLOCK:
signandsets(&current->blocked, &current->blocked, set);
signandsets(&newset, &tsk->blocked, set);
break;
case SIG_SETMASK:
current->blocked = *set;
newset = *set;
break;
default:
error = -EINVAL;
return -EINVAL;
}
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
return error;
spin_lock_irq(&tsk->sighand->siglock);
tsk->blocked = newset;
recalc_sigpending();
spin_unlock_irq(&tsk->sighand->siglock);
return 0;
}
/**