dma-buf: Update reservation shared_count after adding the new fence
We need to serialise the addition of a new fence into the shared list
such that the fence is visible before we claim it is there. Otherwise a
concurrent reader of the shared fence list will see an uninitialised
fence slot before it is set.
<4> [109.613162] general protection fault: 0000 [#1] PREEMPT SMP PTI
<4> [109.613177] CPU: 1 PID: 1357 Comm: gem_busy Tainted: G U 4.19.0-rc8-CI-CI_DRM_5035+ #1
<4> [109.613189] Hardware name: Dell Inc. XPS 8300 /0Y2MRG, BIOS A06 10/17/2011
<4> [109.613252] RIP: 0010:i915_gem_busy_ioctl+0x146/0x380 [i915]
<4> [109.613261] Code: 0b 43 04 49 83 c6 08 4d 39 e6 89 43 04 74 6d 4d 8b 3e e8 5d 54 f4 e0 85 c0 74 0d 80 3d 08 71 1d 00 00
0f 84 bb 00 00 00 31 c0 <49> 81 7f 08 20 3a 2c a0 75 cc 41 8b 97 50 02 00 00 49 8b 8f a8 00
<4> [109.613283] RSP: 0018:
ffffc9000044bcf8 EFLAGS:
00010246
<4> [109.613292] RAX:
0000000000000000 RBX:
ffffc9000044bdc0 RCX:
0000000000000001
<4> [109.613302] RDX:
0000000000000000 RSI:
00000000ffffffff RDI:
ffffffff822474a0
<4> [109.613311] RBP:
ffffc9000044bd28 R08:
ffff88021e158680 R09:
0000000000000001
<4> [109.613321] R10:
0000000000000040 R11:
0000000000000000 R12:
ffff88021e1641b8
<4> [109.613331] R13:
0000000000000003 R14:
ffff88021e1641b0 R15:
6b6b6b6b6b6b6b6b
<4> [109.613341] FS:
00007f9c9fc84980(0000) GS:
ffff880227a40000(0000) knlGS:
0000000000000000
<4> [109.613352] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
<4> [109.613360] CR2:
00007f9c9fcb8000 CR3:
00000002247d4005 CR4:
00000000000606e0
Fixes:
27836b641c1b ("dma-buf: remove shared fence staging in reservation object")
Testcase: igt/gem_busy/close-race
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Christian König <christian.koenig@amd.com>
Cc: Junwei Zhang <Jerry.Zhang@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181026080302.11507-1-chris@chris-wilson.co.uk
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