The following commit has been merged into the sched/core branch of tip:
Commit-ID: dc6e0818bc9a0336d9accf3ea35d146d72aa7a18
Gitweb: https://git.kernel.org/tip/dc6e0818bc9a0336d9accf3ea35d146d72aa7a18
Author: Chengming Zhou <zhouchengming@bytedance.com>
AuthorDate: Sun, 20 Feb 2022 13:14:25 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 01 Mar 2022 16:18:38 +01:00
sched/cpuacct: Optimize away RCU read lock
Since cpuacct_charge() is called from the scheduler update_curr(),
we must already have rq lock held, then the RCU read lock can
be optimized away.
And do the same thing in it's wrapper cgroup_account_cputime(),
but we can't use lockdep_assert_rq_held() there, which defined
in kernel/sched/sched.h.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220220051426.5274-2-zhouchengming@bytedance.com
---
include/linux/cgroup.h | 2 --
kernel/sched/cpuacct.c | 4 +---
2 files changed, 1 insertion(+), 5 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 75c1514..9a109c6 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -791,11 +791,9 @@ static inline void cgroup_account_cputime(struct task_struct *task,
cpuacct_charge(task, delta_exec);
- rcu_read_lock();
cgrp = task_dfl_cgroup(task);
if (cgroup_parent(cgrp))
__cgroup_account_cputime(cgrp, delta_exec);
- rcu_read_unlock();
}
static inline void cgroup_account_cputime_field(struct task_struct *task,
diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 3078005..f79f884 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -337,12 +337,10 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
unsigned int cpu = task_cpu(tsk);
struct cpuacct *ca;
- rcu_read_lock();
+ lockdep_assert_rq_held(cpu_rq(cpu));
for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
*per_cpu_ptr(ca->cpuusage, cpu) += cputime;
-
- rcu_read_unlock();
}
/*