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 23:41:48 +0800 Message-ID: <5136123C.3040508@cn.fujitsu.com> References: <512BBAD8.8010006@linux.vnet.ibm.com> <512C7A38.8060906@linux.vnet.ibm.com> <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> <513232B6.9060905@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <513232B6.9060905@linux.vnet.ibm.com> Sender: linux-pm-owner@vger.kernel.org To: "Srivatsa S. Bhat" Cc: Michel Lespinasse , Oleg Nesterov , 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 01:11, Srivatsa S. Bhat wrote: > On 03/02/2013 06:44 PM, Lai Jiangshan wrote: >> From 345a7a75c314ff567be48983e0892bc69c4452e7 Mon Sep 17 00:00:00 2001 >> From: Lai Jiangshan >> Date: Sat, 2 Mar 2013 20:33:14 +0800 >> Subject: [PATCH] lglock: add read-preference local-global rwlock >> >> Current lglock is not read-preference, so it can't be used on some cases >> which read-preference rwlock can do. Example, get_cpu_online_atomic(). >> > [...] >> diff --git a/kernel/lglock.c b/kernel/lglock.c >> index 6535a66..52e9b2c 100644 >> --- a/kernel/lglock.c >> +++ b/kernel/lglock.c >> @@ -87,3 +87,71 @@ void lg_global_unlock(struct lglock *lg) >> preempt_enable(); >> } >> EXPORT_SYMBOL(lg_global_unlock); >> + >> +#define FALLBACK_BASE (1UL << 30) >> + >> +void lg_rwlock_local_read_lock(struct lgrwlock *lgrw) >> +{ >> + struct lglock *lg = &lgrw->lglock; >> + >> + preempt_disable(); >> + if (likely(!__this_cpu_read(*lgrw->reader_refcnt))) { >> + rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_); >> + if (unlikely(!arch_spin_trylock(this_cpu_ptr(lg->lock)))) { >> + read_lock(&lgrw->fallback_rwlock); >> + __this_cpu_write(*lgrw->reader_refcnt, FALLBACK_BASE); >> + return; >> + } >> + } >> + >> + __this_cpu_inc(*lgrw->reader_refcnt); >> +} >> +EXPORT_SYMBOL(lg_rwlock_local_read_lock); >> + >> +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; > > This should be a break, instead of a return, right? > Otherwise, there will be a preempt imbalance... "lockdep" and "preempt" are handled in lg_local_unlock(&lgrw->lglock); Thanks, Lai > >> + case FALLBACK_BASE: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + read_unlock(&lgrw->fallback_rwlock); >> + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); >> + break; >> + default: >> + __this_cpu_dec(*lgrw->reader_refcnt); >> + break; >> + } >> + >> + preempt_enable(); >> +} > > > Regards, > Srivatsa S. Bhat > > -- > 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 78CF62C032B for ; Wed, 6 Mar 2013 02:39:45 +1100 (EST) Message-ID: <5136123C.3040508@cn.fujitsu.com> Date: Tue, 05 Mar 2013 23:41:48 +0800 From: Lai Jiangshan MIME-Version: 1.0 To: "Srivatsa S. Bhat" Subject: Re: [PATCH V2] lglock: add read-preference local-global rwlock References: <512BBAD8.8010006@linux.vnet.ibm.com> <512C7A38.8060906@linux.vnet.ibm.com> <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> <513232B6.9060905@linux.vnet.ibm.com> In-Reply-To: <513232B6.9060905@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Cc: Lai Jiangshan , linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, 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, Oleg Nesterov , vincent.guittot@linaro.org, sbw@mit.edu, 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 01:11, Srivatsa S. Bhat wrote: > On 03/02/2013 06:44 PM, Lai Jiangshan wrote: >> From 345a7a75c314ff567be48983e0892bc69c4452e7 Mon Sep 17 00:00:00 2001 >> From: Lai Jiangshan >> Date: Sat, 2 Mar 2013 20:33:14 +0800 >> Subject: [PATCH] lglock: add read-preference local-global rwlock >> >> Current lglock is not read-preference, so it can't be used on some cases >> which read-preference rwlock can do. Example, get_cpu_online_atomic(). >> > [...] >> diff --git a/kernel/lglock.c b/kernel/lglock.c >> index 6535a66..52e9b2c 100644 >> --- a/kernel/lglock.c >> +++ b/kernel/lglock.c >> @@ -87,3 +87,71 @@ void lg_global_unlock(struct lglock *lg) >> preempt_enable(); >> } >> EXPORT_SYMBOL(lg_global_unlock); >> + >> +#define FALLBACK_BASE (1UL << 30) >> + >> +void lg_rwlock_local_read_lock(struct lgrwlock *lgrw) >> +{ >> + struct lglock *lg = &lgrw->lglock; >> + >> + preempt_disable(); >> + if (likely(!__this_cpu_read(*lgrw->reader_refcnt))) { >> + rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_); >> + if (unlikely(!arch_spin_trylock(this_cpu_ptr(lg->lock)))) { >> + read_lock(&lgrw->fallback_rwlock); >> + __this_cpu_write(*lgrw->reader_refcnt, FALLBACK_BASE); >> + return; >> + } >> + } >> + >> + __this_cpu_inc(*lgrw->reader_refcnt); >> +} >> +EXPORT_SYMBOL(lg_rwlock_local_read_lock); >> + >> +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; > > This should be a break, instead of a return, right? > Otherwise, there will be a preempt imbalance... "lockdep" and "preempt" are handled in lg_local_unlock(&lgrw->lglock); Thanks, Lai > >> + case FALLBACK_BASE: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + read_unlock(&lgrw->fallback_rwlock); >> + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); >> + break; >> + default: >> + __this_cpu_dec(*lgrw->reader_refcnt); >> + break; >> + } >> + >> + preempt_enable(); >> +} > > > Regards, > Srivatsa S. Bhat > > -- > 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 23:41:48 +0800 Subject: [PATCH V2] lglock: add read-preference local-global rwlock In-Reply-To: <513232B6.9060905@linux.vnet.ibm.com> References: <512BBAD8.8010006@linux.vnet.ibm.com> <512C7A38.8060906@linux.vnet.ibm.com> <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> <513232B6.9060905@linux.vnet.ibm.com> Message-ID: <5136123C.3040508@cn.fujitsu.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/03/13 01:11, Srivatsa S. Bhat wrote: > On 03/02/2013 06:44 PM, Lai Jiangshan wrote: >> From 345a7a75c314ff567be48983e0892bc69c4452e7 Mon Sep 17 00:00:00 2001 >> From: Lai Jiangshan >> Date: Sat, 2 Mar 2013 20:33:14 +0800 >> Subject: [PATCH] lglock: add read-preference local-global rwlock >> >> Current lglock is not read-preference, so it can't be used on some cases >> which read-preference rwlock can do. Example, get_cpu_online_atomic(). >> > [...] >> diff --git a/kernel/lglock.c b/kernel/lglock.c >> index 6535a66..52e9b2c 100644 >> --- a/kernel/lglock.c >> +++ b/kernel/lglock.c >> @@ -87,3 +87,71 @@ void lg_global_unlock(struct lglock *lg) >> preempt_enable(); >> } >> EXPORT_SYMBOL(lg_global_unlock); >> + >> +#define FALLBACK_BASE (1UL << 30) >> + >> +void lg_rwlock_local_read_lock(struct lgrwlock *lgrw) >> +{ >> + struct lglock *lg = &lgrw->lglock; >> + >> + preempt_disable(); >> + if (likely(!__this_cpu_read(*lgrw->reader_refcnt))) { >> + rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_); >> + if (unlikely(!arch_spin_trylock(this_cpu_ptr(lg->lock)))) { >> + read_lock(&lgrw->fallback_rwlock); >> + __this_cpu_write(*lgrw->reader_refcnt, FALLBACK_BASE); >> + return; >> + } >> + } >> + >> + __this_cpu_inc(*lgrw->reader_refcnt); >> +} >> +EXPORT_SYMBOL(lg_rwlock_local_read_lock); >> + >> +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; > > This should be a break, instead of a return, right? > Otherwise, there will be a preempt imbalance... "lockdep" and "preempt" are handled in lg_local_unlock(&lgrw->lglock); Thanks, Lai > >> + case FALLBACK_BASE: >> + __this_cpu_write(*lgrw->reader_refcnt, 0); >> + read_unlock(&lgrw->fallback_rwlock); >> + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); >> + break; >> + default: >> + __this_cpu_dec(*lgrw->reader_refcnt); >> + break; >> + } >> + >> + preempt_enable(); >> +} > > > Regards, > Srivatsa S. Bhat > > -- > 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/ >