-----Original Message----- From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] Sent: Thursday, December 18, 2014 19:21 To: Thierry Reding Cc: Cheng, Yao; intel-gfx@lists.freedesktop.org; dri- devel@lists.freedesktop.org; Kelley, Sean V; Chehab, John; emil.l.velikov@gmail.com; Jiang, Fei Subject: Re: [RFC PATCH v3 4/4] tests/drv_module_reload: add ipvr support
On Thu, Dec 18, 2014 at 11:04 AM, Thierry Reding thierry.reding@gmail.com wrote:
I double checked the symptom and found it was a deadlock on
drm_global_mutex.
When i915_driver_load() registers the platform device while ipvr module
is in the system, ipvr's probe() function tries to lock drm_global_mutex which was already held by i915.
I think either of the following 2 actions need to be moved to a bottom half
e.g. a work queue:
platform_device_add () call in i915_ved.c (called duringi915_driver_load())
drm_dev_register() call during ipvr's probe() Which one makesmore sense? pls kindly advise (I personally prefer the former one.).
Yes, that's somewhat ugly, but I don't see a way around that. I'd also think that moving platform_device_add() to a workqueue would be the best option here.
Or we simply kill drm_global_mutex for platform drivers that don't use the -
probe hook. It should work when they have a correct order betwen
drm_dev_alloc and _register and all the code in between. So just ditch the -
load callback in teh ipvr driver and rework the load sequence as suggested
somewhere else and this is fixed already. No need for bottom halfs I think.
Daniel, sorry I didn't quite understand "platform drivers that don't use the probe hook". For initialization, the ipvr platform driver's probe() is called in following 2 possible paths: 1. ipvr installed before i915. In this case, ipvr's probe() is called inside i915_driver_load() and falls into the drm_global_mutex dead lock. 2. i915 installed before ipvr. In this case, ipvr's probe() is called without drm_global_mutex held by i915 and no dead lock issue. If we kill drm_global_mutex, will path 2 run into issue? And in your suggestion, how to rework the load sequence? Do you mean calling ipvr's load() callback directly during platform driver probe()?
-Daniel
Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch