Messages in this thread | | | Date | Tue, 12 Oct 2021 15:15:50 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] locking/mutex: remove rcu_read_lock/unlock as we already disabled preemption |
| |
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();
> - 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?
| |