From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [PATCH 4/4 V2] ALSA: hda - Continue probe in work context to avoid request_module deadlock Date: Thu, 23 May 2013 08:49:20 +0200 Message-ID: References: <1369273867-2067-1-git-send-email-xingchao.wang@linux.intel.com> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1369273867-2067-1-git-send-email-xingchao.wang@linux.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Wang Xingchao Cc: alsa-devel@alsa-project.org, jocelyn.li@intel.com, mengdong.lin@intel.com, intel-gfx@lists.freedesktop.org, liam.r.girdwood@intel.com, david.henningsson@canonical.com List-Id: alsa-devel@alsa-project.org At Thu, 23 May 2013 09:51:07 +0800, Wang Xingchao wrote: > > There's deadlock when request_module(i915) in azx_probe. > It looks like: > device_lock(audio pci device) -> azx_probe -> module_request > (or symbol_request) -> modprobe (userspace) -> i915 init -> > drm_pci_init -> pci_register_driver -> bus_add_driver -> driver_attach -> > which in turn tries all locks on pci bus, and when it tries the one on the > audio device, it will deadlock. > > This patch introduce a work to store remaining probe stuff, and let > request_module run in safe work context. > > Signed-off-by: Wang Xingchao > --- > sound/pci/hda/hda_i915.c | 13 ++++-- > sound/pci/hda/hda_intel.c | 105 +++++++++++++++++++++++++++------------------- > 2 files changed, 71 insertions(+), 47 deletions(-) > > diff --git a/sound/pci/hda/hda_i915.c b/sound/pci/hda/hda_i915.c > index 76c13d5..7547b20 100644 > --- a/sound/pci/hda/hda_i915.c > +++ b/sound/pci/hda/hda_i915.c > @@ -42,13 +42,18 @@ int hda_i915_init(void) > { > int err = 0; > > - get_power = symbol_request(i915_request_power_well); > + get_power = symbol_get(i915_request_power_well); > if (!get_power) { > - snd_printk(KERN_WARNING "hda-i915: get_power symbol get fail\n"); > - return -ENODEV; > + request_module("i915"); > + get_power = symbol_get(i915_request_power_well); > + if (!get_power) { > + snd_printk(KERN_WARNING "hda-i915: get_power symbol get fail\n"); > + return -ENODEV; > + } > + snd_printdd("hda-i915: get_power symbol get successful\n"); Why do you need this change? Takashi