drm/i915: Verify the engine after acquiring the active.lock

When using virtual engines, the rq->engine is not stable until we hold
the engine->active.lock (as the virtual engine may be exchanged with the
sibling). Since commit 22b7a426 ("drm/i915/execlists: Preempt-to-busy")
we may retire a request concurrently with resubmitting it to HW, we need
to be extra careful to verify we are holding the correct lock for the
request's active list. This is similar to the issue we saw with
rescheduling the virtual requests, see sched_lock_engine().

Or else:

<4> [876.736126] list_add corruption. prev->next should be next (ffff8883f931a1f8), but was dead000000000100. (prev=ffff888361ffa610).
<4> [876.736136] WARNING: CPU: 2 PID: 21 at lib/list_debug.c:28 __list_add_valid+0x4d/0x70
<4> [876.736137] Modules linked in: i915(+) amdgpu gpu_sched ttm vgem snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic mei_hdcp x86_pkg_temp_thermal coretemp crct10dif_pclmul crc32_pclmul snd_intel_nhlt snd_hda_codec snd_hwdep snd_hda_core ghash_clmulni_intel e1000e cdc_ether usbnet mii snd_pcm ptp pps_core mei_me mei prime_numbers btusb btrtl btbcm btintel bluetooth ecdh_generic ecc [last unloaded: i915]
<4> [876.736154] CPU: 2 PID: 21 Comm: ksoftirqd/2 Tainted: G     U            5.3.0-CI-CI_DRM_6898+ #1
<4> [876.736156] Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP TLC, BIOS ICLSFWR1.R00.3183.A00.1905020411 05/02/2019
<4> [876.736157] RIP: 0010:__list_add_valid+0x4d/0x70
<4> [876.736159] Code: c3 48 89 d1 48 c7 c7 20 33 0e 82 48 89 c2 e8 4a 4a bc ff 0f 0b 31 c0 c3 48 89 c1 4c 89 c6 48 c7 c7 70 33 0e 82 e8 33 4a bc ff <0f> 0b 31 c0 c3 48 89 f2 4c 89 c1 48 89 fe 48 c7 c7 c0 33 0e 82 e8
<4> [876.736160] RSP: 0018:ffffc9000018bd30 EFLAGS: 00010082
<4> [876.736162] RAX: 0000000000000000 RBX: ffff888361ffc840 RCX: 0000000000000104
<4> [876.736163] RDX: 0000000080000104 RSI: 0000000000000000 RDI: 00000000ffffffff
<4> [876.736164] RBP: ffffc9000018bd68 R08: 0000000000000000 R09: 0000000000000001
<4> [876.736165] R10: 00000000aed95de3 R11: 000000007fe927eb R12: ffff888361ffca10
<4> [876.736166] R13: ffff888361ffa610 R14: ffff888361ffc880 R15: ffff8883f931a1f8
<4> [876.736168] FS:  0000000000000000(0000) GS:ffff88849fd00000(0000) knlGS:0000000000000000
<4> [876.736169] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4> [876.736170] CR2: 00007f093a9173c0 CR3: 00000003bba08005 CR4: 0000000000760ee0
<4> [876.736171] PKRU: 55555554
<4> [876.736172] Call Trace:
<4> [876.736226]  __i915_request_submit+0x152/0x370 [i915]
<4> [876.736263]  __execlists_submission_tasklet+0x6da/0x1f50 [i915]
<4> [876.736293]  ? execlists_submission_tasklet+0x29/0x50 [i915]
<4> [876.736321]  execlists_submission_tasklet+0x34/0x50 [i915]
<4> [876.736325]  tasklet_action_common.isra.5+0x47/0xb0
<4> [876.736328]  __do_softirq+0xd8/0x4ae
<4> [876.736332]  ? smpboot_thread_fn+0x23/0x280
<4> [876.736334]  ? smpboot_thread_fn+0x6b/0x280
<4> [876.736336]  run_ksoftirqd+0x2b/0x50
<4> [876.736338]  smpboot_thread_fn+0x1d3/0x280
<4> [876.736341]  ? sort_range+0x20/0x20
<4> [876.736343]  kthread+0x119/0x130
<4> [876.736345]  ? kthread_park+0xa0/0xa0
<4> [876.736347]  ret_from_fork+0x24/0x50
<4> [876.736353] irq event stamp: 2290145
<4> [876.736356] hardirqs last  enabled at (2290144): [<ffffffff8123cde8>] __slab_free+0x3e8/0x500
<4> [876.736358] hardirqs last disabled at (2290145): [<ffffffff819cfb4d>] _raw_spin_lock_irqsave+0xd/0x50
<4> [876.736360] softirqs last  enabled at (2290114): [<ffffffff81c0033e>] __do_softirq+0x33e/0x4ae
<4> [876.736361] softirqs last disabled at (2290119): [<ffffffff810b815b>] run_ksoftirqd+0x2b/0x50
<4> [876.736363] WARNING: CPU: 2 PID: 21 at lib/list_debug.c:28 __list_add_valid+0x4d/0x70
<4> [876.736364] ---[ end trace 3e58d6c7356c65bf ]---
<4> [876.736406] ------------[ cut here ]------------
<4> [876.736415] list_del corruption. prev->next should be ffff888361ffca10, but was ffff88840ac2c730
<4> [876.736421] WARNING: CPU: 2 PID: 5490 at lib/list_debug.c:53 __list_del_entry_valid+0x79/0x90
<4> [876.736422] Modules linked in: i915(+) amdgpu gpu_sched ttm vgem snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic mei_hdcp x86_pkg_temp_thermal coretemp crct10dif_pclmul crc32_pclmul snd_intel_nhlt snd_hda_codec snd_hwdep snd_hda_core ghash_clmulni_intel e1000e cdc_ether usbnet mii snd_pcm ptp pps_core mei_me mei prime_numbers btusb btrtl btbcm btintel bluetooth ecdh_generic ecc [last unloaded: i915]
<4> [876.736433] CPU: 2 PID: 5490 Comm: i915_selftest Tainted: G     U  W         5.3.0-CI-CI_DRM_6898+ #1
<4> [876.736435] Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP TLC, BIOS ICLSFWR1.R00.3183.A00.1905020411 05/02/2019
<4> [876.736436] RIP: 0010:__list_del_entry_valid+0x79/0x90
<4> [876.736438] Code: 0b 31 c0 c3 48 89 fe 48 c7 c7 30 34 0e 82 e8 ae 49 bc ff 0f 0b 31 c0 c3 48 89 f2 48 89 fe 48 c7 c7 68 34 0e 82 e8 97 49 bc ff <0f> 0b 31 c0 c3 48 c7 c7 a8 34 0e 82 e8 86 49 bc ff 0f 0b 31 c0 c3
<4> [876.736439] RSP: 0018:ffffc900003ef758 EFLAGS: 00010086
<4> [876.736440] RAX: 0000000000000000 RBX: ffff888361ffc840 RCX: 0000000000000002
<4> [876.736442] RDX: 0000000080000002 RSI: 0000000000000000 RDI: 00000000ffffffff
<4> [876.736443] RBP: ffffc900003ef780 R08: 0000000000000000 R09: 0000000000000001
<4> [876.736444] R10: 000000001418e4b7 R11: 000000007f0ea93b R12: ffff888361ffcab8
<4> [876.736445] R13: ffff88843b6d0000 R14: 000000000000217c R15: 0000000000000001
<4> [876.736447] FS:  00007f4e6f255240(0000) GS:ffff88849fd00000(0000) knlGS:0000000000000000
<4> [876.736448] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4> [876.736449] CR2: 00007f093a9173c0 CR3: 00000003bba08005 CR4: 0000000000760ee0
<4> [876.736450] PKRU: 55555554
<4> [876.736451] Call Trace:
<4> [876.736488]  i915_request_retire+0x224/0x8e0 [i915]
<4> [876.736521]  i915_request_create+0x4b/0x1b0 [i915]
<4> [876.736550]  nop_virtual_engine+0x230/0x4d0 [i915]

Fixes: 22b7a426 ("drm/i915/execlists: Preempt-to-busy")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111695Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190918145453.8800-1-chris@chris-wilson.co.uk
(cherry picked from commit 37fa0de3)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/i915_request.c

@@ -194,6 +194,27 @@ static void free_capture_list(struct i915_request *request)
 	}
 }
 
+static void remove_from_engine(struct i915_request *rq)
+{
+	struct intel_engine_cs *engine, *locked;
+
+	/*
+	 * Virtual engines complicate acquiring the engine timeline lock,
+	 * as their rq->engine pointer is not stable until under that
+	 * engine lock. The simple ploy we use is to take the lock then
+	 * check that the rq still belongs to the newly locked engine.
+	 */
+	locked = READ_ONCE(rq->engine);
+	spin_lock(&locked->active.lock);
+	while (unlikely(locked != (engine = READ_ONCE(rq->engine)))) {
+		spin_unlock(&locked->active.lock);
+		spin_lock(&engine->active.lock);
+		locked = engine;
+	}
+	list_del(&rq->sched.link);
+	spin_unlock(&locked->active.lock);
+}
+
 static bool i915_request_retire(struct i915_request *rq)
 {
 	struct i915_active_request *active, *next;
@@ -259,9 +280,7 @@ static bool i915_request_retire(struct i915_request *rq)
 	 * request that we have removed from the HW and put back on a run
 	 * queue.
 	 */
-	spin_lock(&rq->engine->active.lock);
-	list_del(&rq->sched.link);
-	spin_unlock(&rq->engine->active.lock);
+	remove_from_engine(rq);
 
 	spin_lock(&rq->lock);
 	i915_request_mark_complete(rq);