linux-kernel - Re: [PATCH] KVM: avoid using rcu_dereference

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Message-ID: <20170802201633.GA32403@flask>
Date:   Wed, 2 Aug 2017 22:16:33 +0200
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        borntraeger@...ibm.com
Subject: Re: [PATCH] KVM: avoid using rcu_dereference_protected

2017-08-02 17:55+0200, Paolo Bonzini:
> During teardown, accesses to memslots and buses are using
> rcu_dereference_protected with an always-true condition because
> these accesses are done outside the usual mutexes.  This
> is because the last reference is gone and there cannot be any
> concurrent modifications, but rcu_dereference_protected is
> ugly and unobvious.
> 
> Instead, check the refcount in kvm_get_bus and __kvm_memslots.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---

Probably looks nicer than temporarily taking the slots_lock.
Queued for 4.13,

thanks.