From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753722AbcJDKRr (ORCPT ); Tue, 4 Oct 2016 06:17:47 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49777 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752139AbcJDKRo (ORCPT ); Tue, 4 Oct 2016 06:17:44 -0400 Subject: Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted To: Pan Xinhui , Boqun Feng References: <1475164265-246160-1-git-send-email-borntraeger@de.ibm.com> <1475164265-246160-2-git-send-email-borntraeger@de.ibm.com> <20160930055236.GB22004@tardis.cn.ibm.com> <99d81ce9-8362-1b6b-15e1-e451ed379d50@linux.vnet.ibm.com> Cc: Peter Zijlstra , Martin Schwidefsky , Heiko Carstens , Pan Xinhui , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, xen-devel-request@lists.xenproject.org, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, mingo@redhat.com, paulmck@linux.vnet.ibm.com, will.deacon@arm.com, kernellwp@gmail.com, jgross@suse.com, pbonzini@redhat.com, bsingharora@gmail.com From: Christian Borntraeger Date: Tue, 4 Oct 2016 12:17:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <99d81ce9-8362-1b6b-15e1-e451ed379d50@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16100410-0008-0000-0000-000002D7D6DB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16100410-0009-0000-0000-00001A34E833 Message-Id: <3195b219-28f3-883a-7f3f-c555860098fb@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-10-04_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1610040179 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/30/2016 08:35 AM, Pan Xinhui wrote: > > > 在 2016/9/30 13:52, Boqun Feng 写道: >> On Fri, Sep 30, 2016 at 12:49:52PM +0800, Pan Xinhui wrote: >>> >>> >>> 在 2016/9/29 23:51, Christian Borntraeger 写道: >>>> this implements the s390 backend for commit >>>> "kernel/sched: introduce vcpu preempted check interface" >>>> by reworking the existing smp_vcpu_scheduled into >>>> arch_vcpu_is_preempted. We can then also get rid of the >>>> local cpu_is_preempted function by moving the >>>> CIF_ENABLED_WAIT test into arch_vcpu_is_preempted. >>>> >>>> Signed-off-by: Christian Borntraeger >>>> --- >>> >>> hi, Christian >>> thanks for your patch! >>> >>>> arch/s390/include/asm/spinlock.h | 3 +++ >>>> arch/s390/kernel/smp.c | 9 +++++++-- >>>> arch/s390/lib/spinlock.c | 25 ++++++++----------------- >>>> 3 files changed, 18 insertions(+), 19 deletions(-) >>>> >>>> diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h >>>> index 63ebf37..e16e02f 100644 >>>> --- a/arch/s390/include/asm/spinlock.h >>>> +++ b/arch/s390/include/asm/spinlock.h >>>> @@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new) >>>> return __sync_bool_compare_and_swap(lock, old, new); >>>> } >>>> >>>> +bool arch_vcpu_is_preempted(int cpu); >>>> +#define vcpu_is_preempted arch_vcpu_is_preempted >>>> + >>>> /* >>>> * Simple spin lock operations. There are two variants, one clears IRQ's >>>> * on the local processor, one does not. >>>> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c >>>> index 7b89a75..4aadd16 100644 >>>> --- a/arch/s390/kernel/smp.c >>>> +++ b/arch/s390/kernel/smp.c >>>> @@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address) >>>> return -1; >>>> } >>>> >>>> -int smp_vcpu_scheduled(int cpu) >>> root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/ >>> arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu); >>> arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int cpu) { return 1; } >>> arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu) >>> arch/s390/lib/spinlock.c:44: if (smp_vcpu_scheduled(cpu)) >>> >>>> +bool arch_vcpu_is_preempted(int cpu) >>>> { >>>> - return pcpu_running(pcpu_devices + cpu); >>>> + if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu)) >>>> + return false; >>>> + if (pcpu_running(pcpu_devices + cpu)) >>>> + return false; >>> I saw smp_vcpu_scheduled() returns true always on !SMP system. >>> >>> maybe we can do somegthing silimar. like below >>> >>> #ifndef CONFIG_SMP >>> static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_flag_of(CIF_ENABLED_WAIT, cpu); } >>> #else >>> ... >>> >>> but I can't help thinking that if this is a!SMP system, maybe we could only >>> #ifndef CONFIG_SMP >>> static inline bool arch_vcpu_is_preempted(int cpu) { return false; } >>> #else >> >> Why do we need a vcpu_is_preempted() implementation for UP? Where will >> you use it? >> > yep, I also wonder that :) > > But there is a definitaion of smp_vcpu_scheduled() for !SMP kernel. > So I am a little worried that some code has included this spinlock.h for UP kernel also. > > Hi, Christian > Could you help confirms that your patch works on UP? :) My patch as is seems to work fine for !SMP. So it looks like the extra define is not necessary and we could simply go with v2