linux-kernel - Re: [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard policy

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Date:	Thu, 18 Feb 2016 19:08:10 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krčmář <rkrcmar@...hat.com>,
	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Yuki Shibuya <shibuya.yk@...s.nec.co.jp>
Subject: Re: [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard
 policy



On 17/02/2016 20:14, Radim Krčmář wrote:
> +	/* pit->pit_state.lock was overloaded to prevent userspace from getting
> +	 * an inconsistent state after running multiple KVM_REINJECT_CONTROL
> +	 * ioctls in parallel.  Use a separate lock if that ioctl isn't rare.
> +	 */
> +	mutex_lock(&pit->pit_state.lock);
> +	kvm_pit_set_reinject(pit, control->pit_reinject);
> +	mutex_unlock(&pit->pit_state.lock);

... so in patch 7 concurrent _writes_ of reinject are protected by the
lock, but reads are done outside it (in pit_timer_fn).  WDYT about
making reinject an atomic_t?

Paolo