mirror of
https://github.com/torvalds/linux.git
synced 2026-07-31 03:27:03 +02:00
Linux kernel source tree
38fafa9f39
Customer is reporting a really subtle issue where we get random DMAR
faults, hangs and other nasties for kernel migration jobs when stressing
stuff like s2idle/s3/s4. The explosions seems to happen somewhere
after resuming the system with splats looking something like:
PM: suspend exit
rfkill: input handler disabled
xe 0000:00:02.0: [drm] GT0: Engine reset: engine_class=bcs, logical_mask: 0x2, guc_id=0
xe 0000:00:02.0: [drm] GT0: Timedout job: seqno=24496, lrc_seqno=24496, guc_id=0, flags=0x13 in no process [-1]
xe 0000:00:02.0: [drm] GT0: Kernel-submitted job timed out
The likely cause appears to be a race between suspend cancelling the
worker that processes the free_job()'s, such that we still have pending
jobs to be freed after the cancel. Following from this, on resume the
pending_list will now contain at least one already complete job, but it
looks like we call drm_sched_resubmit_jobs(), which will then call
run_job() on everything still on the pending_list. But if the job was
already complete, then all the resources tied to the job, like the bb
itself, any memory that is being accessed, the iommu mappings etc. might
be long gone since those are usually tied to the fence signalling.
This scenario can be seen in ftrace when running a slightly modified
xe_pm IGT (kernel was only modified to inject artificial latency into
free_job to make the race easier to hit):
xe_sched_job_run: dev=0000:00:02.0, fence=0xffff888276cc8540, seqno=0, lrc_seqno=0, gt=0, guc_id=0, batch_addr=0x000000146910 ...
xe_exec_queue_stop: dev=0000:00:02.0, 3:0x2, gt=0, width=1, guc_id=0, guc_state=0x0, flags=0x13
xe_exec_queue_stop: dev=0000:00:02.0, 3:0x2, gt=0, width=1, guc_id=1, guc_state=0x0, flags=0x4
xe_exec_queue_stop: dev=0000:00:02.0, 4:0x1, gt=1, width=1, guc_id=0, guc_state=0x0, flags=0x3
xe_exec_queue_stop: dev=0000:00:02.0, 1:0x1, gt=1, width=1, guc_id=1, guc_state=0x0, flags=0x3
xe_exec_queue_stop: dev=0000:00:02.0, 4:0x1, gt=1, width=1, guc_id=2, guc_state=0x0, flags=0x3
xe_exec_queue_resubmit: dev=0000:00:02.0, 3:0x2, gt=0, width=1, guc_id=0, guc_state=0x0, flags=0x13
xe_sched_job_run: dev=0000:00:02.0, fence=0xffff888276cc8540, seqno=0, lrc_seqno=0, gt=0, guc_id=0, batch_addr=0x000000146910 ...
.....
xe_exec_queue_memory_cat_error: dev=0000:00:02.0, 3:0x2, gt=0, width=1, guc_id=0, guc_state=0x3, flags=0x13
So the job_run() is clearly triggered twice for the same job, even
though the first must have already signalled to completion during
suspend. We can also see a CAT error after the re-submit.
To prevent this only resubmit jobs on the pending_list that have not yet
signalled.
v2:
- Make sure to re-arm the fence callbacks with sched_start().
v3 (Matt B):
- Stop using drm_sched_resubmit_jobs(), which appears to be deprecated
and just open-code a simple loop such that we skip calling run_job()
on anything already signalled.
Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4856
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 | ||
| .clippy.toml | ||
| .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.