drm/nouveau: Fix race condition in channel refcount handling.
drm/nouveau: Fix race condition in channel refcount handling.

nouveau_channel_put() can be executed after the 'refcount == 0' check
in nouveau_channel_get() and before the channel reference count is
incremented. In that case CPU0 will take the context down while CPU1
thinks it owns the channel and 'refcount == 1'.

Signed-off-by: Francisco Jerez <5906ff32bdd9fd8db196f6ba5ad3afd6f9257ea5@riseup.net>
Signed-off-by: Ben Skeggs <d9f27fb07c1e9f131223ad827fa5179f3846c30b@redhat.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas