From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752719AbaFCIrw (ORCPT ); Tue, 3 Jun 2014 04:47:52 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:49981 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752274AbaFCIru (ORCPT ); Tue, 3 Jun 2014 04:47:50 -0400 Date: Tue, 3 Jun 2014 10:47:35 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: Sasha Levin , Jan Kara , "linux-mm@kvack.org" , Andrew Morton , LKML , Dave Jones , Ingo Molnar Subject: Re: mm,console: circular dependency between console_sem and zone lock Message-ID: <20140603084735.GO11096@twins.programming.kicks-ass.net> References: <536AE5DC.6070307@oracle.com> <20140512162811.GD3685@quack.suse.cz> <538B33D5.8070002@oracle.com> <20140602215529.0c13f91b@gandalf.local.home> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="AXVeTwB1tCcD1nEH" Content-Disposition: inline In-Reply-To: <20140602215529.0c13f91b@gandalf.local.home> 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 --AXVeTwB1tCcD1nEH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 02, 2014 at 09:55:29PM -0400, Steven Rostedt wrote: > Hmm, it failed on a try lock, but on the spinlock within the trylock. I > wonder if we should add this. >=20 > Peter? >=20 > -- Steve >=20 > diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c > index 6815171..6579f84 100644 > --- a/kernel/locking/semaphore.c > +++ b/kernel/locking/semaphore.c > @@ -132,7 +132,9 @@ int down_trylock(struct semaphore *sem) > unsigned long flags; > int count; > =20 > - raw_spin_lock_irqsave(&sem->lock, flags); > + if (!raw_spin_trylock_irqsave(&sem->lock, flags)) > + return 1; > + > count =3D sem->count - 1; > if (likely(count >=3D 0)) > sem->count =3D count; I prefer not to, there is no reason the down_trylock() will fail if that spinlock is contended. We might have just hit the release in progress. But let me stare at the original problem.. --AXVeTwB1tCcD1nEH Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTjYumAAoJEHZH4aRLwOS6T/kP/RbtlCdesCyjgceJgf75Pgz+ DV75gfHHjh2fvJ9opE5sdSvkHHsWwpiqACZ0jWq/2X1ZO49WfJAl/G/7VoX7Xn4G FjVdUHV7/U0KvNwdlo9BYU7yUHTlEuPtYbRmdA19YdoCOCRwq9FQrqRLBvS+vbGA F06YnVIg4jwIFWVf8ZOWinNWvZCgQg95+xg6dgjfbzbW8BwdLXC+JrNvAcmU4ISJ OL8iWBkq4XpREAh41GdHXkkd4GaPAibOKxd/1lj3oaXrbMfWZ2h8nKPzkFhF9zaR SaENdcOBUjj4TcuI0/Oe2XzJRZzNjL7nXZULFaO5YmhqM0Agoli/M0kyra2T2IT2 Orxn5OLenAm8tgmqpWga356/KwbDY1HjDcg8UcztARt388YZ/87IIk3yTECrSVM4 SEjguvyzOL0v04ps554JhqLB8JFojMTPd16hmkFqlcKS2ympBT/mAy1JF5zodmcp zyMW3fnShWWdea+3d76/OmWkCa12PqIkd826nZep/SS+1cRojr+mtxI0xckM0CvH Mdru8mepK/Vgty0/fY0dRr//W6fcUlbsdgBGubjpF54EHC7HcMKrw1nriuK9rfMW 7inBKcX5EVZEbLAm1119pBq0KVbMZ2OOd/rzg3YbmEWIw+kmPvi6GYks0z2i+gLp 7GeVBZElJUHzybHW1Leb =pf/j -----END PGP SIGNATURE----- --AXVeTwB1tCcD1nEH--