At Thu, 23 May 2013 19:41:58 +0200, David Henningsson wrote:
On 05/23/2013 12:29 PM, Wang, Xingchao wrote:
-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Thursday, May 23, 2013 6:27 PM To: Wang, Xingchao Cc: Wang Xingchao; alsa-devel@alsa-project.org; intel-gfx@lists.freedesktop.org; david.henningsson@canonical.com; Girdwood, Liam R; Li, Jocelyn; 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 10:19:27 +0000, Wang, Xingchao wrote:
Hi Takashi,
-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Thursday, May 23, 2013 2:49 PM To: Wang Xingchao Cc: alsa-devel@alsa-project.org; intel-gfx@lists.freedesktop.org; david.henningsson@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@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 getfail\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 symbolget
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.
Well, something is really fishy. The patch can't be accepted only because it just works by moon phase...
I will continue to figure out the reason it doesnot work. :(
To the rescue!
I've tried to track this down, and I think this is a problem in modprobe with blacklisted modules. I've just emailed the kmod maintainer (with Wang Xingchao in cc) and asked for clarification.
Thanks for figuring out!
Takashi