From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753620AbcI3Gf4 (ORCPT ); Fri, 30 Sep 2016 02:35:56 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:56828 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751712AbcI3Gfy (ORCPT ); Fri, 30 Sep 2016 02:35:54 -0400 Subject: Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted To: 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> Cc: Christian Borntraeger , 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: Pan Xinhui Date: Fri, 30 Sep 2016 14:35:38 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160930055236.GB22004@tardis.cn.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16093006-0028-0000-0000-000005B70022 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00005829; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000186; SDB=6.00762975; UDB=6.00363756; IPR=6.00538108; BA=6.00004771; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00012827; XFM=3.00000011; UTC=2016-09-30 06:35:52 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16093006-0029-0000-0000-00002FA8D0D8 Message-Id: <99d81ce9-8362-1b6b-15e1-e451ed379d50@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-09-30_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=8.0.1-1609280000 definitions=main-1609300119 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? :) thanks xinhui > Regards, > Boqun > >> ... >> >> >> thanks >> xinhui >> >>> + return true; >>> } >>> +EXPORT_SYMBOL(arch_vcpu_is_preempted); >>> >>> void smp_yield_cpu(int cpu) >>> { >>> diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c >>> index e5f50a7..e48a48e 100644 >>> --- a/arch/s390/lib/spinlock.c >>> +++ b/arch/s390/lib/spinlock.c >>> @@ -37,15 +37,6 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old) >>> asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock)); >>> } >>> >>> -static inline int cpu_is_preempted(int cpu) >>> -{ >>> - if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu)) >>> - return 0; >>> - if (smp_vcpu_scheduled(cpu)) >>> - return 0; >>> - return 1; >>> -} >>> - >>> void arch_spin_lock_wait(arch_spinlock_t *lp) >>> { >>> unsigned int cpu = SPINLOCK_LOCKVAL; >>> @@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) >>> continue; >>> } >>> /* First iteration: check if the lock owner is running. */ >>> - if (first_diag && cpu_is_preempted(~owner)) { >>> + if (first_diag && arch_vcpu_is_preempted(~owner)) { >>> smp_yield_cpu(~owner); >>> first_diag = 0; >>> continue; >>> @@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) >>> * yield the CPU unconditionally. For LPAR rely on the >>> * sense running status. >>> */ >>> - if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) { >>> + if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) { >>> smp_yield_cpu(~owner); >>> first_diag = 0; >>> } >>> @@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) >>> continue; >>> } >>> /* Check if the lock owner is running. */ >>> - if (first_diag && cpu_is_preempted(~owner)) { >>> + if (first_diag && arch_vcpu_is_preempted(~owner)) { >>> smp_yield_cpu(~owner); >>> first_diag = 0; >>> continue; >>> @@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) >>> * yield the CPU unconditionally. For LPAR rely on the >>> * sense running status. >>> */ >>> - if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) { >>> + if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) { >>> smp_yield_cpu(~owner); >>> first_diag = 0; >>> } >>> @@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw) >>> owner = 0; >>> while (1) { >>> if (count-- <= 0) { >>> - if (owner && cpu_is_preempted(~owner)) >>> + if (owner && arch_vcpu_is_preempted(~owner)) >>> smp_yield_cpu(~owner); >>> count = spin_retry; >>> } >>> @@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev) >>> owner = 0; >>> while (1) { >>> if (count-- <= 0) { >>> - if (owner && cpu_is_preempted(~owner)) >>> + if (owner && arch_vcpu_is_preempted(~owner)) >>> smp_yield_cpu(~owner); >>> count = spin_retry; >>> } >>> @@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw) >>> owner = 0; >>> while (1) { >>> if (count-- <= 0) { >>> - if (owner && cpu_is_preempted(~owner)) >>> + if (owner && arch_vcpu_is_preempted(~owner)) >>> smp_yield_cpu(~owner); >>> count = spin_retry; >>> } >>> @@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu) >>> { >>> if (!cpu) >>> return; >>> - if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu)) >>> + if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu)) >>> return; >>> smp_yield_cpu(~cpu); >>> } >>> >>