Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752405AbbEAVJH (ORCPT ); Fri, 1 May 2015 17:09:07 -0400 Received: from mail-vn0-f49.google.com ([209.85.216.49]:41714 "EHLO mail-vn0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbbEAVJF (ORCPT ); Fri, 1 May 2015 17:09:05 -0400 MIME-Version: 1.0 In-Reply-To: References: <1430502057.4472.255.camel@redhat.com> Date: Fri, 1 May 2015 23:09:04 +0200 Message-ID: Subject: Re: [GIT PULL] VFIO fixes for v4.1-rc2 From: Richard Weinberger To: Linus Torvalds Cc: Alex Williamson , Oleg Nesterov , linux-kernel , kvm Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1981 Lines: 59 ...of course I meant t-> and not current-> On 5/1/15, Richard Weinberger wrote: > On Fri, May 1, 2015 at 8:37 PM, Linus Torvalds > wrote: >> "flush_signals()" is only for kernel threads, where it's a hacky >> alternative to actually handling them (since kernel threads never >> rreturn to user space and cannot really "handle" a signal). But you're >> doing it in the ->remove handler for the device, which can be called >> by arbitrary system processes. This is not a kernel thread thing, as >> far as I can see. >> >> If you cannot handle signals, you damn well shouldn't be using >> "wait_event_interruptible_timeout()" to begin with. Get rid of the >> "interruptible", since it apparently *isn't* interruptible. >> >> So I'm not pulling this. >> >> Now I'm worried that other drivers do insane things like this. I >> wonder if we should add some sanity test to flush_signals() to make >> sure that it can only ever get called from a kernel thread. > > Hmm, a quick grep exposes some questionable users. > At least w1 looks fishy. > drivers/w1/w1_family.c:w1_unregister_family > drivers/w1/w1_int.c:__w1_remove_master_device > > What do you think about a WARN_ON like: > > diff --git a/kernel/signal.c b/kernel/signal.c > index d51c5dd..b4079c3 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -427,6 +427,8 @@ void flush_signals(struct task_struct *t) > { > unsigned long flags; > > + WARN_ON((current->flags & PF_KTHREAD) == 0); > + > spin_lock_irqsave(&t->sighand->siglock, flags); > __flush_signals(t); > spin_unlock_irqrestore(&t->sighand->siglock, flags); > > -- > Thanks, > //richard > -- Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/