linux-kernel - Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.02.1405022134380.6261@ionos.tec.linutronix.de>
Date:	Fri, 2 May 2014 21:36:15 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
cc:	Steven Rostedt <rostedt@...dmis.org>,
	Stanislav Meduna <stano@...una.org>,
	"linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>,
	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25

On Fri, 2 May 2014, Thomas Gleixner wrote:
> On Fri, 2 May 2014, Sebastian Andrzej Siewior wrote:
> > * Steven Rostedt | 2014-04-22 14:16:50 [-0400]:
> > > /*
> > >  * Called by the local, per-CPU timer interrupt on SMP.
> > >  */
> > >@@ -1467,7 +1473,7 @@ void run_local_timers(void)
> > > 		return;
> > > 	}
> > > 
> > >-	if (!spin_do_trylock(&base->lock)) {
> > >+	if (timer_should_raise_softirq(&base->lock)) {
> > > 		raise_softirq(TIMER_SOFTIRQ);
> > > 		return;
> > > 	}
> > 
> > Okay. So Peter said that it is okay to apply this since FULL_NO_HZ users
> > wouldn't complain on UP. I still wouldn't say it is broken but that is a
> > different story.
> > We have two users of this trylock. run_local_timers() which pops up
> > quite often (and you patched here) and the other is
> > get_next_timer_interrupt(). What do you suggest we do here? It is
> > basically the same thing.
> 
> It's different as it CANNOT fail on UP. That's called from the idle
> code and there is no way that anything holds that lock on UP when idle
> runs.

So yeah, you are right, that it's called from irq_exit() so it needs
an annotation at least. Maybe it's really cleaner to make it #if SMP
as well just for clarity raisins.

Thanks,

	tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/