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Subject: Re: [PATCH 3/3] sched: Add cond_resched_rwlock
To:     Peter Zijlstra <peterz@infradead.org>,
        Ben Gardon <bgardon@google.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Peter Shier <pshier@google.com>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>,
        Davidlohr Bueso <dave@stgolabs.net>
References: <20201027164950.1057601-1-bgardon@google.com>
 <20201027164950.1057601-3-bgardon@google.com>
 <20201027184440.GN2628@hirez.programming.kicks-ass.net>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <31db67e0-bd9f-ff6d-2cee-b60ad52f71b2@redhat.com>
Date:   Tue, 27 Oct 2020 19:50:14 +0100
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On 27/10/20 19:44, Peter Zijlstra wrote:
> 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.
> 

If that is an Acked-by, I'll merge them through the KVM tree when time
comes.

Paolo