diff options
author | Liao Chang <liaochang1@huawei.com> | 2023-08-29 10:03:18 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-09-13 10:42:59 +0300 |
commit | 4927edc23edccc55284a8c929323e9fa6c5ce71f (patch) | |
tree | ede5c48e5fd4758ae40c00902dee7234d2efec76 /drivers/cpufreq | |
parent | 96db43aced395844a7abc9a0a5cc702513e3534a (diff) | |
download | linux-4927edc23edccc55284a8c929323e9fa6c5ce71f.tar.xz |
cpufreq: Fix the race condition while updating the transition_task of policy
[ Upstream commit 61bfbf7951ba561dcbdd5357702d3cbc2d447812 ]
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: ca654dc3a93d ("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>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r-- | drivers/cpufreq/cpufreq.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 285ba51b31f6..c8912756fc06 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -450,8 +450,10 @@ void cpufreq_freq_transition_end(struct cpufreq_policy *policy, policy->cur, policy->cpuinfo.max_freq); + spin_lock(&policy->transition_lock); policy->transition_ongoing = false; policy->transition_task = NULL; + spin_unlock(&policy->transition_lock); wake_up(&policy->transition_wait); } |