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Umesh Nerlige Ramappa 7d73c60215 drm/i915/pmu: Fix KMD and GuC race on accessing busyness 
GuC updates shared memory and KMD reads it. Since this is not
synchronized, we run into a race where the value read is inconsistent.
Sometimes the inconsistency is in reading the upper MSB bytes of the
last_switch_in value. 2 types of cases are seen - upper 8 bits are zero
and upper 24 bits are zero. Since these are non-zero values, it is
not trivial to determine validity of these values. Instead we read the
values multiple times until they are consistent. In test runs, 3
attempts results in consistent values. The upper bound is set to 6
attempts and may need to be tuned as per any new occurences.

Since the duration that gt is parked can vary, the patch also updates
the gt timestamp on unpark before starting the worker.

v2:
- Initialize i
- Use READ_ONCE to access engine record

Fixes: 77cdd054dd ("drm/i915/pmu: Connect engine busyness stats from GuC to pmu")
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220125020124.788679-2-umesh.nerlige.ramappa@intel.com
(cherry picked from commit 512712a824)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
2022-02-01 08:59:25 +00:00
arch - Add another Intel CPU model to the list of CPUs supporting the 2022-01-30 12:55:06 +02:00
block block: add bio_start_io_acct_time() to control start_time 2022-01-28 12:28:15 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto lib/crypto: add prompts back to crypto libraries 2022-01-18 13:03:55 +01:00
Documentation - Drop an unused private data field in the AIC driver 2022-01-30 15:12:02 +02:00
drivers drm/i915/pmu: Fix KMD and GuC race on accessing busyness 2022-02-01 08:59:25 +00:00
fs ocfs2: fix a deadlock when commit trans 2022-01-30 09:56:58 +02:00
include psi: fix "no previous prototype" warnings when CONFIG_CGROUPS=n 2022-01-30 09:56:58 +02:00
init lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() 2022-01-22 08:33:37 +02:00
ipc proc: remove PDE_DATA() completely 2022-01-22 08:33:37 +02:00
kernel - Prevent accesses to the per-CPU cgroup context list from another CPU 2022-01-30 15:02:32 +02:00
lib kasan: test: fix compatibility with FORTIFY_SOURCE 2022-01-30 09:56:58 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm memory-failure: fetch compound_head after pgmap_pfn_valid() 2022-01-30 09:56:58 +02:00
net \n 2022-01-28 17:51:31 +02:00
samples Merge branch 'akpm' (patches from Andrew) 2022-01-20 10:41:01 +02:00
scripts ftrace: Have architectures opt-in for mcount build time sorting 2022-01-27 19:15:44 -05:00
security Fix NULL pointer crash in LSM via Ceph, from Vivek Goyal <vgoyal@redhat.com>. 2022-01-29 08:52:27 +02:00
sound proc: remove PDE_DATA() completely 2022-01-22 08:33:37 +02:00
tools tools/testing/scatterlist: add missing defines 2022-01-30 09:56:58 +02:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt Two larger x86 series: 2022-01-28 19:00:26 +02:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address of Brian Silverman 2022-01-24 18:27:23 +01:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Removing Ohad from remoteproc/rpmsg maintenance 2021-12-08 10:09:40 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Networking fixes for 5.17-rc2, including fixes from netfilter and can. 2022-01-27 20:58:39 +02:00
Makefile Linux 5.17-rc2 2022-01-30 15:37:07 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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 Restructured Text 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.