From: Paolo Bonzini <pbonzini@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Yuki Shibuya <shibuya.yk@ncos.nec.co.jp>
Subject: Re: [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard policy
Date: Fri, 19 Feb 2016 16:06:10 +0100 [thread overview]
Message-ID: <56C72F62.5060307@redhat.com> (raw)
In-Reply-To: <20160219150434.GA25910@potion.brq.redhat.com>
On 19/02/2016 16:04, Radim Krčmář wrote:
>> >
>> > ... 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?
> There was/is no harm in having reinject non-atomic. This patch added
> notifiers, which is the reason for re-introducing a mutex.
>
> Userspace can (and SHOULDN'T) call this function multiple times,
> concurrently, so the mutex prevents a situations where, e.g. only one
> notifier is registered in the end.
Yes, I understand why you added the mutex here; good catch indeed. The
atomic_t is just to show that it's okay to read it outside the lock.
It's just for a bit of extra documentation.
Paolo
next prev parent reply other threads:[~2016-02-19 15:06 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-17 19:14 [PATCH v2 00/14] KVM: x86: change PIT discard policy and untangle related code Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 01/14] KVM: x86: change PIT discard tick policy Radim Krčmář
2016-02-18 16:13 ` Paolo Bonzini
2016-02-18 16:56 ` Radim Krčmář
2016-02-18 17:33 ` Paolo Bonzini
2016-02-18 17:55 ` Paolo Bonzini
2016-02-19 14:44 ` Radim Krčmář
2016-02-25 12:34 ` Peter Krempa
2016-02-25 13:38 ` Paolo Bonzini
2016-02-25 17:36 ` Radim Krčmář
2016-02-25 19:11 ` Paolo Bonzini
2016-02-26 13:44 ` Radim Krčmář
2016-02-18 18:49 ` Paolo Bonzini
2016-02-17 19:14 ` [PATCH v2 02/14] KVM: x86: simplify atomics in kvm_pit_ack_irq Radim Krčmář
2016-02-18 18:04 ` Paolo Bonzini
2016-02-19 15:51 ` Radim Krčmář
2016-02-19 15:56 ` Paolo Bonzini
2016-02-17 19:14 ` [PATCH v2 03/14] KVM: x86: add kvm_pit_reset_reinject Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 04/14] KVM: x86: use atomic_t instead of pit.inject_lock Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 05/14] KVM: x86: tone down WARN_ON pit.state_lock Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 06/14] KVM: x86: pass struct kvm_pit instead of kvm in PIT Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 07/14] KVM: x86: remove unnecessary uses of PIT state lock Radim Krčmář
2016-02-18 18:03 ` Paolo Bonzini
2016-02-19 14:45 ` Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard policy Radim Krčmář
2016-02-18 18:05 ` Paolo Bonzini
2016-02-18 18:08 ` Paolo Bonzini
2016-02-19 15:04 ` Radim Krčmář
2016-02-19 15:06 ` Paolo Bonzini [this message]
2016-02-19 15:09 ` Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 09/14] KVM: x86: refactor kvm_create_pit Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 10/14] KVM: x86: refactor kvm_free_pit Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 11/14] KVM: x86: remove pit and kvm from kvm_kpit_state Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 12/14] KVM: x86: remove pointless dereference of PIT Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 13/14] KVM: x86: don't assume layout of kvm_kpit_state Radim Krčmář
2016-02-17 19:14 ` [PATCH v2 14/14] KVM: x86: move PIT timer function initialization Radim Krčmář
2016-02-18 18:11 ` [PATCH v2 00/14] KVM: x86: change PIT discard policy and untangle related code Paolo Bonzini
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