5.10-stable review patch. If anyone has any objections, please let me know.
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From: Chengming Zhou zhouchengming@bytedance.com
commit 248cc9993d1cc12b8e9ed716cc3fc09f6c3517dd upstream.
The cpuacct_account_field() is always called by the current task itself, so it's ok to use __this_cpu_add() to charge the tick time.
But cpuacct_charge() maybe called by update_curr() in load_balance() on a random CPU, different from the CPU on which the task is running. So __this_cpu_add() will charge that cputime to a random incorrect CPU.
Fixes: 73e6aafd9ea8 ("sched/cpuacct: Simplify the cpuacct code") Reported-by: Minye Zhu zhuminye@bytedance.com Signed-off-by: Chengming Zhou zhouchengming@bytedance.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Tejun Heo tj@kernel.org Link: https://lore.kernel.org/r/20220220051426.5274-1-zhouchengming@bytedance.com Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/cpuacct.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c index 8a260115a137b..3c59c541dd314 100644 --- a/kernel/sched/cpuacct.c +++ b/kernel/sched/cpuacct.c @@ -328,12 +328,13 @@ static struct cftype files[] = { */ void cpuacct_charge(struct task_struct *tsk, u64 cputime) { + unsigned int cpu = task_cpu(tsk); struct cpuacct *ca;
rcu_read_lock();
for (ca = task_ca(tsk); ca; ca = parent_ca(ca)) - __this_cpu_add(*ca->cpuusage, cputime); + *per_cpu_ptr(ca->cpuusage, cpu) += cputime;
rcu_read_unlock(); }