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@xxxxxxxxxxxxx> AuthorDate: Sun, 20 Feb 2022 13:14:25 +08:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220220051426.5274-2-zhouchengming@xxxxxxxxxxxxx --- 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(); } /*
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