Re: [PATCH 40/41] ncpfs: Use set_current_blocked()

Oleg Nesterov
2011-08-16T17:59:39Z

On 08/11, Matt Fleming wrote:
>
> As described in e6fa16ab ("signal: sigprocmask() should do
> retarget_shared_pending()") the modification of current->blocked is
> incorrect as we need to check whether the signal we're about to block
> is pending in the shared queue.

I'd wish I could understand this code but this seems impossible ;)
IOW, "This doesn't seem right at all." looks reasonable, and the
PF_EXITING adds even more confusion.

As for this patch, it looks (almost) fine anyway. But,

> @@ -749,7 +749,7 @@ static int ncp_do_request(struct ncp_server *server, int size,
> return -EIO;
> }
> {
> - sigset_t old_set;
> + sigset_t old_set, blocked;
> unsigned long mask, flags;
>
> spin_lock_irqsave(&current->sighand->siglock, flags);
> @@ -769,16 +769,14 @@ static int ncp_do_request(struct ncp_server *server, int size,
> if (current->sighand->action[SIGQUIT - 1].sa.sa_handler == SIG_DFL)
> mask |= sigmask(SIGQUIT);
> }
> - siginitsetinv(&current->blocked, mask);
> - recalc_sigpending();
> +
> + siginitsetinv(&blocked, mask);
> + __set_task_blocked(current, &blocked);
> spin_unlock_irqrestore(&current->sighand->siglock, flags);

Why do we take ->siglock in the first place?

I think it is not needed. We can calculate mask/blocked lockless and
use set_task_blocked(). This also makes sense because __set_task_blocked
is not exported ;)

the sighand->action[] checks are racy anyway in the mt case, siglock
can't help.

Oleg.