From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-35557-1526662819-5-7642031917127365744 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-charsets: plain='utf-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: linux@kroah.com X-Delivered-to: linux@kroah.com X-Mail-from: linux-fsdevel-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1526662819; b=SoeF3EwlgUJ8VP+PgOugw8shNYtsTg7WUunOxiEm5vVaATzHH4 OLtqLuxD2uvsuZdcu1gyg0DF2yMUvW07AsbJV0G/awgjl3oiWjXApLX3y5JqMFPB 0w9sBD1lbUQGeaO+snfh1rQoH31nfkVEXZapaF668MR4K8Ie0lE3jNwfdlO7w98A CTfIymaC1Ywz4s8io8JSKpNQjUEEYxuS0KIroJRm3j9HwfdU6Jgbzmf73dVS6+JV Y3XubYP4baFDqq03MMKXCKyHg9/umivazgkpQXC+PMyOMY7ihHmtEl2jpB5cjdUd SdaGt+MLSwO+acB6x/yzHBi6ydCVJzMVRDBg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=subject:to:cc:references:from:message-id :date:mime-version:in-reply-to:content-type :content-transfer-encoding:sender:list-id; s=fm2; t=1526662819; bh=4/7IIFAuMzh5nKRY4S/yW5HBnNxsF2nJpz4f+XX/PDo=; b=nd41hbDw5/XV eL+isoNoZWpliNtQTdWCkRyFmiryF4qC8Vs8XvZ594ci8dO3PqXb3m1uhoa46B01 tUnANhC1xLBb2Qe8zW5EOPPTp83ZKa+9j+SWw0wCf4uskFaQr2gRarR5HQHAKVFo eekfo3A3r0DOwMdbMXMF8VZacJ7h8Kb0G7c0DhE413ER6obqg0RVcjvpDKwlmaVG zxncTuItBuaT85y0WGgw/tDT7q5ybRXKSZLBisVNytmRQMnpKlkfV2yYRShrGjXj HvWb8RaPTHeHfTqipeaHqTqd12bhEly9JLPK9RX9OlyhMqPMFuraO75qd69cZtha klhDd+QbCw== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=redhat.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-fsdevel-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=redhat.com header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=redhat.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-fsdevel-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=redhat.com header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfNyorLTRkfL8RpHZ/xEsjqkoNfGQC/Fjg+GmaMYOpwNW43Vg4Nv2bYy1+trhaepyjsaJGwgfP0Rk6+YsnT1EkpQCtTtbr+Gr2H/DRsACYlzVkh9DYCpq UDTTX9dAoNQsDCeA2Nqhwx1RKrZOGmn0qYqUnryct8JxdGb7OOF/jFAkuAQATI3fr97N24u/IdJ1OXA5C3VRRFYmwc5j8YEVmM0M5Zqa+IHzDeG0uVM0gYNr X-CM-Analysis: v=2.3 cv=JLoVTfCb c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=IkcTkHD0fZMA:10 a=VUJBJC2UJ8kA:10 a=20KFwNOVAAAA:8 a=CkAG0TsrSNbMCQj8eOYA:9 a=QEXdDO2ut3YA:10 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752536AbeERRAQ (ORCPT ); Fri, 18 May 2018 13:00:16 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42150 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751488AbeERRAN (ORCPT ); Fri, 18 May 2018 13:00:13 -0400 Subject: Re: [PATCH] locking/rwsem: simplify the is-owner-spinnable checks To: Oleg Nesterov , Ingo Molnar Cc: Matthew Wilcox , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Davidlohr Bueso , "Theodore Y. Ts'o" , Amir Goldstein , Jan Kara References: <1526420991-21213-1-git-send-email-longman@redhat.com> <1526420991-21213-2-git-send-email-longman@redhat.com> <20180516121947.GE20670@bombadil.infradead.org> <20180518070258.GA20971@gmail.com> <20180518084122.GA14307@redhat.com> <20180518094052.GA26150@gmail.com> <20180518165534.GA22348@redhat.com> From: Waiman Long Organization: Red Hat Message-ID: Date: Fri, 18 May 2018 13:00:11 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180518165534.GA22348@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-fsdevel-owner@vger.kernel.org X-Mailing-List: linux-fsdevel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 05/18/2018 12:55 PM, Oleg Nesterov wrote: > Add the trivial owner_on_cpu() helper for rwsem_can_spin_on_owner() and > rwsem_spin_on_owner(), it also allows to make rwsem_can_spin_on_owner() > a bit more clear. > > Signed-off-by: Oleg Nesterov > --- > kernel/locking/rwsem-xadd.c | 25 +++++++++++++------------ > 1 file changed, 13 insertions(+), 12 deletions(-) > > diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c > index a903367..3064c50 100644 > --- a/kernel/locking/rwsem-xadd.c > +++ b/kernel/locking/rwsem-xadd.c > @@ -347,6 +347,15 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem) > } > } > > +static inline bool owner_on_cpu(struct task_struct *owner) > +{ > + /* > + * As lock holder preemption issue, we both skip spinning if > + * task is not on cpu or its cpu is preempted > + */ > + return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner)); > +} > + > static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) > { > struct task_struct *owner; > @@ -359,17 +368,10 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) > > rcu_read_lock(); > owner = READ_ONCE(sem->owner); > - if (!owner || !is_rwsem_owner_spinnable(owner)) { > - ret = !owner; /* !owner is spinnable */ > - goto done; > + if (owner) { > + ret = is_rwsem_owner_spinnable(owner) && > + owner_on_cpu(owner); > } > - > - /* > - * As lock holder preemption issue, we both skip spinning if task is not > - * on cpu or its cpu is preempted > - */ > - ret = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner)); > -done: > rcu_read_unlock(); > return ret; > } > @@ -398,8 +400,7 @@ static noinline bool rwsem_spin_on_owner(struct rw_semaphore *sem) > * abort spinning when need_resched or owner is not running or > * owner's cpu is preempted. > */ > - if (!owner->on_cpu || need_resched() || > - vcpu_is_preempted(task_cpu(owner))) { > + if (need_resched() || !owner_on_cpu(owner)) { > rcu_read_unlock(); > return false; > } Acked-by: Waiman Long