5.15-stable review patch. If anyone has any objections, please let me know.
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From: Cheng Yu serein.chengyu@huawei.com
[ Upstream commit 49217ea147df7647cb89161b805c797487783fc0 ]
In the cgroup v2 CPU subsystem, assuming we have a cgroup named 'test', and we set cpu.max and cpu.max.burst:
# echo 1000000 > /sys/fs/cgroup/test/cpu.max # echo 1000000 > /sys/fs/cgroup/test/cpu.max.burst
then we check cpu.max and cpu.max.burst:
# cat /sys/fs/cgroup/test/cpu.max 1000000 100000 # cat /sys/fs/cgroup/test/cpu.max.burst 1000000
Next we set cpu.max again and check cpu.max and cpu.max.burst:
# echo 2000000 > /sys/fs/cgroup/test/cpu.max # cat /sys/fs/cgroup/test/cpu.max 2000000 100000
# cat /sys/fs/cgroup/test/cpu.max.burst 1000
... we find that the cpu.max.burst value changed unexpectedly.
In cpu_max_write(), the unit of the burst value returned by tg_get_cfs_burst() is microseconds, while in cpu_max_write(), the burst unit used for calculation should be nanoseconds, which leads to the bug.
To fix it, get the burst value directly from tg->cfs_bandwidth.burst.
Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller") Reported-by: Qixin Liao liaoqixin@huawei.com Signed-off-by: Cheng Yu serein.chengyu@huawei.com Signed-off-by: Zhang Qiao zhangqiao22@huawei.com Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Vincent Guittot vincent.guittot@linaro.org Tested-by: Vincent Guittot vincent.guittot@linaro.org Link: https://lore.kernel.org/r/20240424132438.514720-1-serein.chengyu@huawei.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 25b8ea91168ea..b43da6201b9aa 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -10828,7 +10828,7 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of, { struct task_group *tg = css_tg(of_css(of)); u64 period = tg_get_cfs_period(tg); - u64 burst = tg_get_cfs_burst(tg); + u64 burst = tg->cfs_bandwidth.burst; u64 quota; int ret;