[PATCH RFC 006/111] staging: etnaviv: fix oops on unbind

[Lucas Stach]

From: Russell King <rmk+kernel at arm.linux.org.uk>

The oops below was found when unbinding the etnaviv drm driver.  This is
caused by using drm_gem_object_unreference() in a region which is not
protected by drm_dev->struct_mutex.  Fix this by using
drm_gem_object_unreference_unlocked() instead.

Kernel BUG at c026cab8 [verbose debug info unavailable]
Internal error: Oops - BUG: 0 [#1] PREEMPT ARM
Modules linked in: etnaviv(C-) ...
task: d41dda80 ti: d63f2000 task.ti: d63f2000
PC is at drm_gem_object_free+0x34/0x38
LR is at etnaviv_gpu_unbind+0x7c/0xb0 [etnaviv]
pc : [<c026cab8>]    lr : [<bf1067a8>]    psr: 600d0013
sp : d63f3da0  ip : d63f3db0  fp : d63f3dac
r10: 00020000  r9 : d63f2000  r8 : c000ece8
r7 : d4386c34  r6 : d4386c00  r5 : d42c4d80  r4 : d621ac10
r3 : d4386c00  r2 : 00000001  r1 : d608c410  r0 : d59da580
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 10c5387d  Table: 14234019  DAC: 00000015
Process rmmod (pid: 1633, stack limit = 0xd63f2250)
[<c026ca84>] (drm_gem_object_free) from [<bf1067a8>] (etnaviv_gpu_unbind+0x7c/0xb0 [etnaviv])
[<bf10672c>] (etnaviv_gpu_unbind [etnaviv]) from [<c028a47c>] (component_unbind+0x38/0x70)
[<c028a444>] (component_unbind) from [<c028a52c>] (component_unbind_all+0x78/0xac)
[<c028a4b4>] (component_unbind_all) from [<bf104560>] (etnaviv_unload+0x68/0x7c [etnaviv])
[<bf1044f8>] (etnaviv_unload [etnaviv]) from [<c0270498>] (drm_dev_unregister+0x2c/0xa0)
[<c0270c90>] (drm_put_dev) from [<bf104058>] (etnaviv_unbind+0x14/0x18 [etnaviv])
[<bf104044>] (etnaviv_unbind [etnaviv]) from [<c028a2a4>] (take_down_master+0x2c/0x4c)
...

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/staging/etnaviv/etnaviv_gpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/etnaviv/etnaviv_gpu.c b/drivers/staging/etnaviv/etnaviv_gpu.c
index e3b93c293dca..8e44493038cb 100644
--- a/drivers/staging/etnaviv/etnaviv_gpu.c
+++ b/drivers/staging/etnaviv/etnaviv_gpu.c
@@ -868,7 +868,7 @@ static void etnaviv_gpu_unbind(struct device *dev, struct device *master,
 	WARN_ON(!list_empty(&gpu->active_list));
 
 	if (gpu->buffer)
-		drm_gem_object_unreference(gpu->buffer);
+		drm_gem_object_unreference_unlocked(gpu->buffer);
 
 	if (gpu->mmu)
 		etnaviv_iommu_destroy(gpu->mmu);
-- 
2.1.4