From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH V2] lglock: add read-preference local-global rwlock Date: Tue, 5 Mar 2013 17:41:06 +0100 Message-ID: <20130305164106.GA4329@redhat.com> References: <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> <51360ED1.3030104@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <51360ED1.3030104@cn.fujitsu.com> Sender: linux-doc-owner@vger.kernel.org To: Lai Jiangshan 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-pm@vger.kernel.org On 03/05, Lai Jiangshan wrote: > > 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) Yes, I was wrong thanks. Another case when I didn't notice that you re-use the regular lg_ code... > > 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. I am not sure which one should be better too, please check. Again, I forgot that _write_lock/unlock use lg_global_*() code. Oleg.