drm/i915: Keep drm_i915_file_private around under RCU
Ensure that the drm_i915_file_private continues to exist as we attempt
to remove a request from its list, which may race with the destruction
of the file.
<6> [38.380714] [IGT] gem_ctx_create: starting subtest basic-files
<0> [42.201329] BUG: spinlock bad magic on CPU#0, kworker/u16:0/7
<4> [42.201356] general protection fault: 0000 [#1] PREEMPT SMP PTI
<4> [42.201371] CPU: 0 PID: 7 Comm: kworker/u16:0 Tainted: G U 5.3.0-rc5-CI-Patchwork_14169+ #1
<4> [42.201391] Hardware name: Dell Inc. OptiPlex 745 /0GW726, BIOS 2.3.1 05/21/2007
<4> [42.201594] Workqueue: i915 retire_work_handler [i915]
<4> [42.201614] RIP: 0010:spin_dump+0x5a/0x90
<4> [42.201625] Code: 00 48 8d 88 c0 06 00 00 48 c7 c7 00 71 09 82 e8 35 ef 00 00 48 85 db 44 8b 4d 08 41 b8 ff ff ff ff 48 c7 c1 0b cd 0f 82 74 0e <44> 8b 83 e0 04 00 00 48 8d 8b c0 06 00 00 8b 55 04 48 89 ee 48 c7
<4> [42.201660] RSP: 0018:
ffffc9000004bd80 EFLAGS:
00010202
<4> [42.201673] RAX:
0000000000000031 RBX:
6b6b6b6b6b6b6b6b RCX:
ffffffff820fcd0b
<4> [42.201688] RDX:
0000000000000000 RSI:
ffff88803de266f8 RDI:
00000000ffffffff
<4> [42.201703] RBP:
ffff888038381ff8 R08:
00000000ffffffff R09:
000000006b6b6b6b
<4> [42.201718] R10:
0000000041cb0b89 R11:
646162206b636f6c R12:
ffff88802a618500
<4> [42.201733] R13:
ffff88802b32c288 R14:
ffff888038381ff8 R15:
ffff88802b32c250
<4> [42.201748] FS:
0000000000000000(0000) GS:
ffff88803de00000(0000) knlGS:
0000000000000000
<4> [42.201765] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
<4> [42.201778] CR2:
00007f2cefc6d180 CR3:
00000000381ee000 CR4:
00000000000006f0
<4> [42.201793] Call Trace:
<4> [42.201805] do_raw_spin_lock+0x66/0xb0
<4> [42.201898] i915_request_retire+0x548/0x7c0 [i915]
<4> [42.201989] retire_requests+0x4d/0x60 [i915]
<4> [42.202078] i915_retire_requests+0x144/0x2e0 [i915]
<4> [42.202169] retire_work_handler+0x10/0x40 [i915]
Recently, in commit
44c22f3f1a0a ("drm/i915: Serialize insertion into the
file->mm.request_list"), we fixed a race on insertion. Now, it appears
we also have a race with destruction!
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190823181455.31910-1-chris@chris-wilson.co.uk
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