Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752872AbaDWIuk (ORCPT ); Wed, 23 Apr 2014 04:50:40 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:43837 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752709AbaDWIuf (ORCPT ); Wed, 23 Apr 2014 04:50:35 -0400 Date: Wed, 23 Apr 2014 10:50:31 +0200 From: Peter Zijlstra To: Sebastian Andrzej Siewior Cc: Steven Rostedt , Stanislav Meduna , "linux-rt-users@vger.kernel.org" , Linux ARM Kernel , "linux-kernel@vger.kernel.org" , Thomas Gleixner Subject: Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25 Message-ID: <20140423085031.GI11096@twins.programming.kicks-ass.net> References: <534C3606.7010206@meduna.org> <534C731F.1050406@meduna.org> <534DADF1.6060608@meduna.org> <20140422115439.GA20669@linutronix.de> <20140422094657.5b6ca1e2@gandalf.local.home> <20140422140918.GE11096@twins.programming.kicks-ass.net> <53577559.9090501@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53577559.9090501@linutronix.de> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 23, 2014 at 10:10:01AM +0200, Sebastian Andrzej Siewior wrote: > On 04/22/2014 04:09 PM, Peter Zijlstra wrote: > > On Tue, Apr 22, 2014 at 09:46:57AM -0400, Steven Rostedt wrote: > >>> According to lockdep a trylock should not fail on UP. > > > > Oh!? Where does it say that? A trylock can fail at all times. > > kernel/locking/spinlock_debug.c: > > int do_raw_spin_trylock(raw_spinlock_t *lock) > { > int ret = arch_spin_trylock(&lock->raw_lock); > > if (ret) > debug_spin_lock_after(lock); > #ifndef CONFIG_SMP > /* > * Must not happen on UP: > */ > SPIN_BUG_ON(!ret, lock, "trylock failure on UP"); > #endif > return ret; > } > > How can a trylock (spinlock, not mutex) fail on UP? That would mean the > lock is not interrupt safe. > Unless, you attempt to take the lock from interrupt context via trylock > while in general you take the spinlock in process context with > interrupts enabled. But that's not lockdep. That's the spinlock debugging code, entirely different beasts. -- 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/