From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lai Jiangshan Subject: Re: [PATCH V2] lglock: add read-preference local-global rwlock Date: Tue, 05 Mar 2013 23:27:13 +0800 Message-ID: <51360ED1.3030104@cn.fujitsu.com> References: <512CC509.1050000@linux.vnet.ibm.com> <512D0D67.9010609@linux.vnet.ibm.com> <512E7879.20109@linux.vnet.ibm.com> <5130E8E2.50206@cn.fujitsu.com> <20130301182854.GA3631@redhat.com> <5131FB4C.7070408@cn.fujitsu.com> <20130302172003.GC29769@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130302172003.GC29769@redhat.com> Sender: linux-pm-owner@vger.kernel.org To: Oleg Nesterov Cc: Michel Lespinasse , "Srivatsa S. Bhat" , Lai Jiangshan , linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, namhyung@kernel.org, mingo@kernel.org, linux-arch@vger.kernel.org, linux@arm.linux.org.uk, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, paulmck@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, rostedt@goodmis.org, rjw@sisk.pl, vincent.guittot@linaro.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, sbw@mit.edu, tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org List-Id: linux-arch.vger.kernel.org On 03/03/13 01:20, Oleg Nesterov wrote: > On 03/02, Lai Jiangshan wrote: >> >> +void lg_rwlock_local_read_unlock(struct lgrwlock *lgrw) >> +{ >> + switch (__this_cpu_read(*lgrw->reader_refcnt)) { >> + case 1: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + lg_local_unlock(&lgrw->lglock); >> + return; >> + case FALLBACK_BASE: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + read_unlock(&lgrw->fallback_rwlock); >> + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); > > I guess "case 1:" should do rwlock_release() too. Already do it in "lg_local_unlock(&lgrw->lglock);" before it returns. (I like reuse old code) > > Otherwise, at first glance looks correct... > > However, I still think that FALLBACK_BASE only adds the unnecessary > complications. But even if I am right this is subjective of course, please > feel free to ignore. OK, I kill FALLBACK_BASE in later patch. > > And btw, I am not sure about lg->lock_dep_map, perhaps we should use > fallback_rwlock->dep_map ? Use either one is OK. > > We need rwlock_acquire_read() even in the fast-path, and this acquire_read > should be paired with rwlock_acquire() in _write_lock(), but it does > spin_acquire(lg->lock_dep_map). Yes, currently this is the same (afaics) > but perhaps fallback_rwlock->dep_map would be more clean. > I can't tell which one is better. I try to use fallback_rwlock->dep_map later. > Oleg. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from song.cn.fujitsu.com (unknown [222.73.24.84]) by ozlabs.org (Postfix) with ESMTP id A0A7A2C0320 for ; Wed, 6 Mar 2013 02:25:13 +1100 (EST) Message-ID: <51360ED1.3030104@cn.fujitsu.com> Date: Tue, 05 Mar 2013 23:27:13 +0800 From: Lai Jiangshan MIME-Version: 1.0 To: Oleg Nesterov Subject: Re: [PATCH V2] lglock: add read-preference local-global rwlock References: <512CC509.1050000@linux.vnet.ibm.com> <512D0D67.9010609@linux.vnet.ibm.com> <512E7879.20109@linux.vnet.ibm.com> <5130E8E2.50206@cn.fujitsu.com> <20130301182854.GA3631@redhat.com> <5131FB4C.7070408@cn.fujitsu.com> <20130302172003.GC29769@redhat.com> In-Reply-To: <20130302172003.GC29769@redhat.com> Content-Type: text/plain; charset=UTF-8 Cc: Lai Jiangshan , linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, Michel Lespinasse , mingo@kernel.org, linux-arch@vger.kernel.org, linux@arm.linux.org.uk, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, paulmck@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, rostedt@goodmis.org, rjw@sisk.pl, namhyung@kernel.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, vincent.guittot@linaro.org, sbw@mit.edu, "Srivatsa S. Bhat" , tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 03/03/13 01:20, Oleg Nesterov wrote: > On 03/02, Lai Jiangshan wrote: >> >> +void lg_rwlock_local_read_unlock(struct lgrwlock *lgrw) >> +{ >> + switch (__this_cpu_read(*lgrw->reader_refcnt)) { >> + case 1: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + lg_local_unlock(&lgrw->lglock); >> + return; >> + case FALLBACK_BASE: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + read_unlock(&lgrw->fallback_rwlock); >> + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); > > I guess "case 1:" should do rwlock_release() too. Already do it in "lg_local_unlock(&lgrw->lglock);" before it returns. (I like reuse old code) > > Otherwise, at first glance looks correct... > > However, I still think that FALLBACK_BASE only adds the unnecessary > complications. But even if I am right this is subjective of course, please > feel free to ignore. OK, I kill FALLBACK_BASE in later patch. > > And btw, I am not sure about lg->lock_dep_map, perhaps we should use > fallback_rwlock->dep_map ? Use either one is OK. > > We need rwlock_acquire_read() even in the fast-path, and this acquire_read > should be paired with rwlock_acquire() in _write_lock(), but it does > spin_acquire(lg->lock_dep_map). Yes, currently this is the same (afaics) > but perhaps fallback_rwlock->dep_map would be more clean. > I can't tell which one is better. I try to use fallback_rwlock->dep_map later. > Oleg. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > From mboxrd@z Thu Jan 1 00:00:00 1970 From: laijs@cn.fujitsu.com (Lai Jiangshan) Date: Tue, 05 Mar 2013 23:27:13 +0800 Subject: [PATCH V2] lglock: add read-preference local-global rwlock In-Reply-To: <20130302172003.GC29769@redhat.com> References: <512CC509.1050000@linux.vnet.ibm.com> <512D0D67.9010609@linux.vnet.ibm.com> <512E7879.20109@linux.vnet.ibm.com> <5130E8E2.50206@cn.fujitsu.com> <20130301182854.GA3631@redhat.com> <5131FB4C.7070408@cn.fujitsu.com> <20130302172003.GC29769@redhat.com> Message-ID: <51360ED1.3030104@cn.fujitsu.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/03/13 01:20, Oleg Nesterov wrote: > On 03/02, Lai Jiangshan wrote: >> >> +void lg_rwlock_local_read_unlock(struct lgrwlock *lgrw) >> +{ >> + switch (__this_cpu_read(*lgrw->reader_refcnt)) { >> + case 1: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + lg_local_unlock(&lgrw->lglock); >> + return; >> + case FALLBACK_BASE: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + read_unlock(&lgrw->fallback_rwlock); >> + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); > > I guess "case 1:" should do rwlock_release() too. Already do it in "lg_local_unlock(&lgrw->lglock);" before it returns. (I like reuse old code) > > Otherwise, at first glance looks correct... > > However, I still think that FALLBACK_BASE only adds the unnecessary > complications. But even if I am right this is subjective of course, please > feel free to ignore. OK, I kill FALLBACK_BASE in later patch. > > And btw, I am not sure about lg->lock_dep_map, perhaps we should use > fallback_rwlock->dep_map ? Use either one is OK. > > We need rwlock_acquire_read() even in the fast-path, and this acquire_read > should be paired with rwlock_acquire() in _write_lock(), but it does > spin_acquire(lg->lock_dep_map). Yes, currently this is the same (afaics) > but perhaps fallback_rwlock->dep_map would be more clean. > I can't tell which one is better. I try to use fallback_rwlock->dep_map later. > Oleg. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >