Hi Takashi, > -----Original Message----- > From: Takashi Iwai [mailto:tiwai at suse.de] > Sent: Thursday, May 23, 2013 2:49 PM > To: Wang Xingchao > Cc: alsa-devel at alsa-project.org; intel-gfx at lists.freedesktop.org; > david.henningsson at canonical.com; Girdwood, Liam R; Li, Jocelyn; Wang, > Xingchao; Lin, Mengdong > Subject: Re: [PATCH 4/4 V2] ALSA: hda - Continue probe in work context to avoid > request_module deadlock > > 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 <xingchao.wang at linux.intel.com> > > --- > > 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? > symbol_request() should be the better API in such case but in my test it doesnot really load i915 module, that's why I call request_module(i915) directly here. Please note there's parameter difference: request_module("i915") symbol_request(i915_reauest_power_well)-->request_module("symbol:i915_request_power_well") I donot know why the second one did not really load the module. Thanks --xingchao
