https://bugs.freedesktop.org/show_bug.cgi?id=29140
--- Comment #9 from steckdenis@yahoo.fr 2010-08-12 09:57:45 PDT --- Hello,
I think I found the problem, but I am unfortunately unable to fix it (I don't know the radeon module enough).
A change between the 2.6.34 and 2.6.35 kernels added a bunch of functions in drivers/gpu/drm/radeon/radeon_pm.c. The function that causes troubles to me is radeon_pm_set_clocks(struct radeon_device *rdev); .
This function begins by locking three mutexes, including rdev->cp.mutex.
My card is a r300, so the code goes through the "else" branch of the if. This branch contains a call to radeon_fence_emit.
Now in radeon_fence.c . I don't know how, but this function happens to call radeon_fence_wait. The problem is that radeon_fence_wait calls r300_gpu_is_lockup, by branching in "if (unlikely(!radeon_fence_signaled(fence))) {".
In r300.c : r300_gpu_is_lockup, called by radeon_fence_wait, calls radeon_ring_lock, because it wants to write in the ring.
In radeon_ring.c : radeon_ring_lock begins by calling "mutex_lock(&rdev->cp.mutex);", the exact same mutex as the one already locked by radeon_pm_set_clocks. That seems to be the problem.
Cheers.