Messages in this thread | | | Subject | Re: [PATCH v2] locking/mutex: remove rcu_read_lock/unlock as we already disabled preemption | From | "Xu, Yanfei" <> | Date | Wed, 13 Oct 2021 15:54:02 +0800 |
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On 10/12/21 9:15 PM, Peter Zijlstra wrote: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > On Fri, Oct 08, 2021 at 11:25:18AM +0800, Yanfei Xu wrote: >> preempt_disable/enable() is equal to RCU read-side crital section, >> and the mutex lock slowpath disabled the preemption for the optimistic >> spinning code. Let's remove the rcu_read_lock/unlock for saving some >> cycles in hot codes. >> >> Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com> >> --- >> v1->v2: fix the incorrect comment in code and commit message. >> thanks for WaiMan's suggestion. >> >> BTW, sorry for this late v2 due to a long vocation. >> >> kernel/locking/mutex.c | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c >> index 2fede72b6af5..2f654cfb10d9 100644 >> --- a/kernel/locking/mutex.c >> +++ b/kernel/locking/mutex.c >> @@ -351,13 +351,14 @@ bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner, >> { >> bool ret = true; > > lockdep_assert_preemption_disabled();
Agree.
> >> - rcu_read_lock(); >> while (__mutex_owner(lock) == owner) { >> /* >> * Ensure we emit the owner->on_cpu, dereference _after_ > > And did you check the other code in locking/ for similar things? >
I did a check, rwsem also has the similar things. Will do it for rwsem in v3.
Thanks, Yanfei
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