On Tue, Aug 01, 2006 at 08:25:12AM -0700, Linus Torvalds wrote:
>
>
> On Tue, 1 Aug 2006, Paul E. McKenney wrote:
> > >
> > > Paul? Should I just revert, or did you have some deeper reason for it?
> >
> > I cannot claim any deep thought on this one, so please do revert it.
>
> Well, I do have to say that I like the notion of trying to have the _same_
> semantics for "force_sig_info()" and "force_sig_specific()", so in that
> way your patch is fine - I just missed the fact that it changed it back to
> the old broken ones (that results in endless SIGSEGV's if the SIGSEGV
> happens when setting up the handler for the SIGSEGV and other
> "interesting" issues, where a bug can result in the user process hanging
> instead of just killing it outright).
>
> However, I wonder if the _proper_ fix is to just either remove
> "force_sig_specific()" entirely, or just make that one match the semantics
> of "force_sig_info()" instead (rather than doing it the other way - change
> for_sig_specific() to match force_sig_info()).
>
> force_sig_info() has only two uses, and both should be ok with the
> force_sig_specific() semantics, since they are for SIGSTOP and SIGKILL
> respectively, and those should not be blockable unless you're a kernel
> thread (and I don't think either of them could validly ever be used with
> kernel threads anyway), so doing it the other way around _should_ be ok.
>
> Paul, Suresh, would something like this work for you instead?
Yes.
Acked-by: Suresh Siddha <[email protected]>
>
> Linus
> ----
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 7fe874d..bfdb568 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -791,22 +791,31 @@ out:
> /*
> * Force a signal that the process can't ignore: if necessary
> * we unblock the signal and change any SIG_IGN to SIG_DFL.
> + *
> + * Note: If we unblock the signal, we always reset it to SIG_DFL,
> + * since we do not want to have a signal handler that was blocked
> + * be invoked when user space had explicitly blocked it.
> + *
> + * We don't want to have recursive SIGSEGV's etc, for example.
> */
> -
> int
> force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
> {
> unsigned long int flags;
> - int ret;
> + int ret, blocked, ignored;
> + struct k_sigaction *action;
>
> spin_lock_irqsave(&t->sighand->siglock, flags);
> - if (t->sighand->action[sig-1].sa.sa_handler == SIG_IGN) {
> - t->sighand->action[sig-1].sa.sa_handler = SIG_DFL;
> - }
> - if (sigismember(&t->blocked, sig)) {
> - sigdelset(&t->blocked, sig);
> + action = &t->sighand->action[sig-1];
> + ignored = action->sa.sa_handler == SIG_IGN;
> + blocked = sigismember(&t->blocked, sig);
> + if (blocked || ignored) {
> + action->sa.sa_handler = SIG_DFL;
> + if (blocked) {
> + sigdelset(&t->blocked, sig);
> + recalc_sigpending_tsk(t);
> + }
> }
> - recalc_sigpending_tsk(t);
> ret = specific_send_sig_info(sig, info, t);
> spin_unlock_irqrestore(&t->sighand->siglock, flags);
>
-
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