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Date:   Tue, 27 Oct 2020 13:17:30 -0700
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Ben Gardon <bgardon@google.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Peter Shier <pshier@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>
Subject: Re: [PATCH 3/3] sched: Add cond_resched_rwlock
Message-ID: <20201027201730.kyusnssnrict75bh@linux-p48b.lan>
References: <20201027164950.1057601-1-bgardon@google.com>
 <20201027164950.1057601-3-bgardon@google.com>
 <20201027175634.GI1021@linux.intel.com>
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On Tue, 27 Oct 2020, Sean Christopherson wrote:

>On Tue, Oct 27, 2020 at 09:49:50AM -0700, Ben Gardon wrote:
>> Rescheduling while holding a spin lock is essential for keeping long
>> running kernel operations running smoothly. Add the facility to
>> cond_resched rwlocks.

Nit: I would start the paragraph with 'Safely rescheduling ...'
While obvious when reading the code, 'Rescheduling while holding
a spin lock' can throw the reader off.

>
>This adds two new exports and two new macros without any in-tree users, which
>is generally frowned upon.  You and I know these will be used by KVM's new
>TDP MMU, but the non-KVM folks, and more importantly the maintainers of this
>code, are undoubtedly going to ask "why".  I.e. these patches probably belong
>in the KVM series to switch to a rwlock for the TDP MMU.
>
>Regarding the code, it's all copy-pasted from the spinlock code and darn near
>identical.  It might be worth adding builder macros for these.

Agreed, all three could be nicely consolidated. Otherwise this series looks
sane, feel free to add my:

Acked-by: Davidlohr Bueso <dbueso@suse.de>