Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760349AbYG1Ut6 (ORCPT ); Mon, 28 Jul 2008 16:49:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752446AbYG1Utu (ORCPT ); Mon, 28 Jul 2008 16:49:50 -0400 Received: from ns2.gothnet.se ([82.193.160.251]:7217 "EHLO GOTHNET-SMTP2.gothnet.se" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753906AbYG1Uts (ORCPT ); Mon, 28 Jul 2008 16:49:48 -0400 X-Greylist: delayed 956 seconds by postgrey-1.27 at vger.kernel.org; Mon, 28 Jul 2008 16:49:48 EDT Message-ID: <488E2CED.1040207@tungstengraphics.com> Date: Mon, 28 Jul 2008 22:32:45 +0200 From: =?ISO-8859-1?Q?Thomas_Hellstr=F6m?= User-Agent: Thunderbird 2.0.0.12 (X11/20080306) MIME-Version: 1.0 To: Dave Airlie CC: Jiri Slaby , airlied@linux.ie, Andrew Morton , dri-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1 repost #1] DRM: don't enable irqs in locking References: <1216975369-6749-1-git-send-email-jirislaby@gmail.com> <21d7e9970807250154q4a1958f5k45f62408e97ae3c7@mail.gmail.com> In-Reply-To: <21d7e9970807250154q4a1958f5k45f62408e97ae3c7@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-BitDefender-Scanner: Mail not scanned due to license constraints Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4400 Lines: 115 Dave Airlie wrote: > On Fri, Jul 25, 2008 at 6:42 PM, Jiri Slaby wrote: > >> drm_lock_take(); and drm_lock_free(); are called from >> drm_locked_tasklet_func(); which disables interrupts when grabbing its >> spinlock. >> >> Don't allow these locking functions to re-enable interrupts when >> the tasklet expects them disabled. I.e. use spin_lock_irqsave instead of >> spin_lock_bh (with their unlock opposites). >> > > Hmm this has bounced through 2-3 variations.. Thomas any ideas what > the final correct answer is? > > Dave. > Hmm, Yes, this bug could occur, but the remedy is not to use spin_lock_irqsave() for lock_data::spinlock but to avoid calling drm_lock_take with the drm_device::tasklet_lock held with irqs disabled. I'll see if I can come up with a patch. /Thomas >> We will get such a warnings otherwise: >> ------------[ cut here ]------------ >> WARNING: at kernel/softirq.c:136 local_bh_enable_ip+0x8b/0xb0() >> Modules linked in: arc4 ecb crypto_blkcipher cryptomgr crypto_algapi ath5k usbhid mac80211 ohci1394 hid led_class floppy cfg80211 ff_memless ieee1394 rtc_cmos evdev [last unloaded: freq_table] >> Pid: 0, comm: swapper Not tainted 2.6.26-rc8-mm1_64 #427 >> >> Call Trace: >> [] warn_on_slowpath+0x5f/0x90 >> [...] >> [] local_bh_enable_ip+0x8b/0xb0 >> [] _spin_unlock_bh+0xf/0x20 >> [] drm_lock_take+0x81/0xe0 >> [] drm_locked_tasklet_func+0x4b/0xb0 >> [] tasklet_hi_action+0x69/0xf0 >> [] __do_softirq+0x84/0xf0 >> [stack snipped] >> >> Signed-off-by: Jiri Slaby >> Cc: David Airlie >> --- >> drivers/gpu/drm/drm_lock.c | 12 +++++++----- >> 1 files changed, 7 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_lock.c b/drivers/gpu/drm/drm_lock.c >> index 0998723..79943e4 100644 >> --- a/drivers/gpu/drm/drm_lock.c >> +++ b/drivers/gpu/drm/drm_lock.c >> @@ -196,10 +196,11 @@ int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) >> int drm_lock_take(struct drm_lock_data *lock_data, >> unsigned int context) >> { >> + unsigned long flags; >> unsigned int old, new, prev; >> volatile unsigned int *lock = &lock_data->hw_lock->lock; >> >> - spin_lock_bh(&lock_data->spinlock); >> + spin_lock_irqsave(&lock_data->spinlock, flags); >> do { >> old = *lock; >> if (old & _DRM_LOCK_HELD) >> @@ -211,7 +212,7 @@ int drm_lock_take(struct drm_lock_data *lock_data, >> } >> prev = cmpxchg(lock, old, new); >> } while (prev != old); >> - spin_unlock_bh(&lock_data->spinlock); >> + spin_unlock_irqrestore(&lock_data->spinlock, flags); >> >> if (_DRM_LOCKING_CONTEXT(old) == context) { >> if (old & _DRM_LOCK_HELD) { >> @@ -270,17 +271,18 @@ static int drm_lock_transfer(struct drm_lock_data *lock_data, >> */ >> int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context) >> { >> + unsigned long flags; >> unsigned int old, new, prev; >> volatile unsigned int *lock = &lock_data->hw_lock->lock; >> >> - spin_lock_bh(&lock_data->spinlock); >> + spin_lock_irqsave(&lock_data->spinlock, flags); >> if (lock_data->kernel_waiters != 0) { >> drm_lock_transfer(lock_data, 0); >> lock_data->idle_has_lock = 1; >> - spin_unlock_bh(&lock_data->spinlock); >> + spin_unlock_irqrestore(&lock_data->spinlock, flags); >> return 1; >> } >> - spin_unlock_bh(&lock_data->spinlock); >> + spin_unlock_irqrestore(&lock_data->spinlock, flags); >> >> do { >> old = *lock; >> -- >> 1.5.6.2 >> >> -- >> 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/ >> >> -- 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/