linux-kernel - Re: [PATCH 3/3] sched: Add cond_resched

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Date:   Tue, 27 Oct 2020 19:44:40 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Peter Shier <pshier@...gle.com>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH 3/3] sched: Add cond_resched_rwlock

On Tue, Oct 27, 2020 at 09:49:50AM -0700, Ben Gardon wrote:

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index d2003a7d5ab55..ac58e7829a063 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6152,6 +6152,46 @@ int __cond_resched_lock(spinlock_t *lock)
>  }
>  EXPORT_SYMBOL(__cond_resched_lock);
>  
> +int __cond_resched_rwlock_read(rwlock_t *lock)
> +{
> +	int resched = should_resched(PREEMPT_LOCK_OFFSET);
> +	int ret = 0;
> +
> +	lockdep_assert_held(lock);

	lockdep_assert_held_read(lock);

> +
> +	if (rwlock_needbreak(lock) || resched) {
> +		read_unlock(lock);
> +		if (resched)
> +			preempt_schedule_common();
> +		else
> +			cpu_relax();
> +		ret = 1;
> +		read_lock(lock);
> +	}
> +	return ret;
> +}
> +EXPORT_SYMBOL(__cond_resched_rwlock_read);
> +
> +int __cond_resched_rwlock_write(rwlock_t *lock)
> +{
> +	int resched = should_resched(PREEMPT_LOCK_OFFSET);
> +	int ret = 0;
> +
> +	lockdep_assert_held(lock);

	lockdep_assert_held_write(lock);

> +
> +	if (rwlock_needbreak(lock) || resched) {
> +		write_unlock(lock);
> +		if (resched)
> +			preempt_schedule_common();
> +		else
> +			cpu_relax();
> +		ret = 1;
> +		write_lock(lock);
> +	}
> +	return ret;
> +}
> +EXPORT_SYMBOL(__cond_resched_rwlock_write);

If this is the only feedback (the patches look fine to me), don't bother
resending, I'll edit them when applying.