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Originally, with strict in order execution, we could complete execution
only when the queue was empty. Preempt-to-busy allows replacement of an
active request that may complete before the preemption is processed by
HW. If that happens, the request is retired from the queue, but the
queue_priority_hint remains set, preventing direct submission until
after the next CS interrupt is processed.
This preempt-to-busy race can be triggered by the heartbeat, which will
also act as the power-management barrier and upon completion allow us to
idle the HW. We may process the completion of the heartbeat, and begin
parking the engine before the CS event that restores the
queue_priority_hint, causing us to fail the assertion that it is MIN.
<3>[ 166.210729] __engine_park:283 GEM_BUG_ON(engine->sched_engine->queue_priority_hint != (-((int)(~0U >> 1)) - 1))
<0>[ 166.210781] Dumping ftrace buffer:
<0>[ 166.210795] ---------------------------------
...
<0>[ 167.302811] drm_fdin-1097 2..s1. 165741070us : trace_ports: 0000:00:02.0 rcs0: promote { ccid:20 1217:2 prio 0 }
<0>[ 167.302861] drm_fdin-1097 2d.s2. 165741072us : execlists_submission_tasklet: 0000:00:02.0 rcs0: preempting last=1217:2, prio=0, hint=2147483646
<0>[ 167.302928] drm_fdin-1097 2d.s2. 165741072us : __i915_request_unsubmit: 0000:00:02.0 rcs0: fence 1217:2, current 0
<0>[ 167.302992] drm_fdin-1097 2d.s2. 165741073us : __i915_request_submit: 0000:00:02.0 rcs0: fence 3:4660, current 4659
<0>[ 167.303044] drm_fdin-1097 2d.s1. 165741076us : execlists_submission_tasklet: 0000:00:02.0 rcs0: context:3 schedule-in, ccid:40
<0>[ 167.303095] drm_fdin-1097 2d.s1. 165741077us : trace_ports: 0000:00:02.0 rcs0: submit { ccid:40 3:4660* prio 2147483646 }
<0>[ 167.303159] kworker/-89 11..... 165741139us : i915_request_retire.part.0: 0000:00:02.0 rcs0: fence c90:2, current 2
<0>[ 167.303208] kworker/-89 11..... 165741148us : __intel_context_do_unpin: 0000:00:02.0 rcs0: context:c90 unpin
<0>[ 167.303272] kworker/-89 11..... 165741159us : i915_request_retire.part.0: 0000:00:02.0 rcs0: fence 1217:2, current 2
<0>[ 167.303321] kworker/-89 11..... 165741166us : __intel_context_do_unpin: 0000:00:02.0 rcs0: context:1217 unpin
<0>[ 167.303384] kworker/-89 11..... 165741170us : i915_request_retire.part.0: 0000:00:02.0 rcs0: fence 3:4660, current 4660
<0>[ 167.303434] kworker/-89 11d..1. 165741172us : __intel_context_retire: 0000:00:02.0 rcs0: context:1216 retire runtime: { total:56028ns, avg:56028ns }
<0>[ 167.303484] kworker/-89 11..... 165741198us : __engine_park: 0000:00:02.0 rcs0: parked
<0>[ 167.303534] <idle>-0 5d.H3. 165741207us : execlists_irq_handler: 0000:00:02.0 rcs0: semaphore yield: 00000040
<0>[ 167.303583] kworker/-89 11..... 165741397us : __intel_context_retire: 0000:00:02.0 rcs0: context:1217 retire runtime: { total:325575ns, avg:0ns }
<0>[ 167.303756] kworker/-89 11..... 165741777us : __intel_context_retire: 0000:00:02.0 rcs0: context:c90 retire runtime: { total:0ns, avg:0ns }
<0>[ 167.303806] kworker/-89 11..... 165742017us : __engine_park: __engine_park:283 GEM_BUG_ON(engine->sched_engine->queue_priority_hint != (-((int)(~0U >> 1)) - 1))
<0>[ 167.303811] ---------------------------------
<4>[ 167.304722] ------------[ cut here ]------------
<2>[ 167.304725] kernel BUG at drivers/gpu/drm/i915/gt/intel_engine_pm.c:283!
<4>[ 167.304731] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
<4>[ 167.304734] CPU: 11 PID: 89 Comm: kworker/11:1 Tainted: G W 6.8.0-rc2-CI_DRM_14193-gc655e0fd2804+ #1
<4>[ 167.304736] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022
<4>[ 167.304738] Workqueue: i915-unordered retire_work_handler [i915]
<4>[ 167.304839] RIP: 0010:__engine_park+0x3fd/0x680 [i915]
<4>[ 167.304937] Code: 00 48 c7 c2 b0 e5 86 a0 48 8d 3d 00 00 00 00 e8 79 48 d4 e0 bf 01 00 00 00 e8 ef 0a d4 e0 31 f6 bf 09 00 00 00 e8 03 49 c0 e0 <0f> 0b 0f 0b be 01 00 00 00 e8 f5 61 fd ff 31 c0 e9 34 fd ff ff 48
<4>[ 167.304940] RSP: 0018:ffffc9000059fce0 EFLAGS: 00010246
<4>[ 167.304942] RAX: 0000000000000200 RBX: 0000000000000000 RCX: 0000000000000006
<4>[ 167.304944] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000009
<4>[ 167.304946] RBP: ffff8881330ca1b0 R08: 0000000000000001 R09: 0000000000000001
<4>[ 167.304947] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8881330ca000
<4>[ 167.304948] R13: ffff888110f02aa0 R14: ffff88812d1d0205 R15: ffff88811277d4f0
<4>[ 167.304950] FS: 0000000000000000(0000) GS:ffff88844f780000(0000) knlGS:0000000000000000
<4>[ 167.304952] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[ 167.304953] CR2: 00007fc362200c40 CR3: 000000013306e003 CR4: 0000000000770ef0
<4>[ 167.304955] PKRU: 55555554
<4>[ 167.304957] Call Trace:
<4>[ 167.304958] <TASK>
<4>[ 167.305573] ____intel_wakeref_put_last+0x1d/0x80 [i915]
<4>[ 167.305685] i915_request_retire.part.0+0x34f/0x600 [i915]
<4>[ 167.305800] retire_requests+0x51/0x80 [i915]
<4>[ 167.305892] intel_gt_retire_requests_timeout+0x27f/0x700 [i915]
<4>[ 167.305985] process_scheduled_works+0x2db/0x530
<4>[ 167.305990] worker_thread+0x18c/0x350
<4>[ 167.305993] kthread+0xfe/0x130
<4>[ 167.305997] ret_from_fork+0x2c/0x50
<4>[ 167.306001] ret_from_fork_asm+0x1b/0x30
<4>[ 167.306004] </TASK>
It is necessary for the queue_priority_hint to be lower than the next
request submission upon waking up, as we rely on the hint to decide when
to kick the tasklet to submit that first request.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.