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Liao Chang d6f80ddb9e cpufreq: Fix the race condition while updating the transition_task of policy 
[ Upstream commit 61bfbf7951 ]

The field 'transition_task' of policy structure is used to track the
task which is performing the frequency transition. Using this field to
print a warning once detect a case where the same task is calling
_begin() again before completing the preivous frequency transition via
the _end().

However, there is a potential race condition in _end() and _begin() APIs
while updating the field 'transition_task' of policy, the scenario is
depicted below:

             Task A                            Task B

        /* 1st freq transition */
        Invoke _begin() {
                ...
                ...
        }
                                        /* 2nd freq transition */
                                        Invoke _begin() {
                                                ... //waiting for A to
                                                ... //clear
                                                ... //transition_ongoing
                                                ... //in _end() for
                                                ... //the 1st transition
                                                        |
        Change the frequency                            |
                                                        |
        Invoke _end() {                                 |
                ...                                     |
                ...                                     |
                transition_ongoing = false;             V
                                                transition_ongoing = true;
                                                transition_task = current;
                transition_task = NULL;
                ... //A overwrites the task
                ... //performing the transition
                ... //result in error warning.
        }

To fix this race condition, the transition_lock of policy structure is
now acquired before updating policy structure in _end() API. Which ensure
that only one task can update the 'transition_task' field at a time.

Link: https://lore.kernel.org/all/b3c61d8a-d52d-3136-fbf0-d1de9f1ba411@huawei.com/
Fixes: ca654dc3a9 ("cpufreq: Catch double invocations of cpufreq_freq_transition_begin/end")
Signed-off-by: Liao Chang <liaochang1@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-09-19 12:22:49 +02:00
arch um: Fix hostaudio build errors 2023-09-19 12:22:49 +02:00
block block/partition: fix signedness issue for Amiga partitions 2023-07-23 13:47:37 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: api - Use work queue in crypto_destroy_instance 2023-09-19 12:22:33 +02:00
Documentation ACPI: thermal: Drop nocrt parameter 2023-09-02 09:17:07 +02:00
drivers cpufreq: Fix the race condition while updating the transition_task of policy 2023-09-19 12:22:49 +02:00
fs pNFS: Fix assignment of xprtdata.cred 2023-09-19 12:22:43 +02:00
include scsi: core: Use 32-bit hostnum in scsi_host_lookup() 2023-09-19 12:22:47 +02:00
init x86/mm: Initialize text poking earlier 2023-08-08 19:58:33 +02:00
io_uring io_uring: fix drain stalls by invalid SQE 2023-09-19 12:22:39 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel tracing: Fix race issue between cpu buffer write and swap 2023-09-19 12:22:48 +02:00
lib radix tree: remove unused variable 2023-08-30 16:18:18 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm net-memcg: Fix scope of sockmem pressure indicators 2023-09-19 12:22:33 +02:00
net netrom: Deny concurrent connect(). 2023-09-19 12:22:35 +02:00
samples samples/bpf: fix broken map lookup probe 2023-09-19 12:22:34 +02:00
scripts kbuild: Disable GCOV for *.mod.o 2023-07-23 13:47:17 +02:00
security smackfs: Prevent underflow in smk_set_cipso() 2023-09-19 12:22:39 +02:00
sound um: Fix hostaudio build errors 2023-09-19 12:22:49 +02:00
tools selftests/bpf: Clean up fmod_ret in bench_rename test script 2023-09-19 12:22:33 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:22:40 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.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: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 iio: stx104: Move to addac subdirectory 2023-08-26 14:23:27 +02:00
Makefile Linux 5.15.131 2023-09-06 21:28:41 +01:00
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.