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Message-ID: <20190805144318.GA972@tardis>
Date: Mon, 5 Aug 2019 22:43:18 +0800
From: Boqun Feng <boqun.feng@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Will Deacon <will@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, bigeasy@...utronix.de,
juri.lelli@...hat.com, williams@...hat.com, bristot@...hat.com,
longman@...hat.com, dave@...olabs.net, jack@...e.com
Subject: Re: [PATCH] locking/percpu_rwsem: Rewrite to not use rwsem
On Mon, Aug 05, 2019 at 04:02:41PM +0200, Peter Zijlstra wrote:
[...]
>
> static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
> {
> + rwsem_release(&sem->dep_map, 1, _RET_IP_);
> +
> preempt_disable();
> /*
> * Same as in percpu_down_read().
> */
> - if (likely(rcu_sync_is_idle(&sem->rss)))
> + if (likely(rcu_sync_is_idle(&sem->rss))) {
> __this_cpu_dec(*sem->read_count);
> - else
> - __percpu_up_read(sem); /* Unconditional memory barrier */
> - preempt_enable();
> + preempt_enable();
> + return;
> + }
>
> - rwsem_release(&sem->rw_sem.dep_map, 1, _RET_IP_);
Missing a preempt_enable() here?
Regards,
Boqun
> + __percpu_up_read(sem); /* Unconditional memory barrier */
> }
>
[...]
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