Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423589Ab3CVXBI (ORCPT ); Fri, 22 Mar 2013 19:01:08 -0400 Received: from mail-ia0-f169.google.com ([209.85.210.169]:64496 "EHLO mail-ia0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423377Ab3CVXBG (ORCPT ); Fri, 22 Mar 2013 19:01:06 -0400 MIME-Version: 1.0 In-Reply-To: <1363809337-29718-8-git-send-email-riel@surriel.com> References: <1363809337-29718-1-git-send-email-riel@surriel.com> <1363809337-29718-8-git-send-email-riel@surriel.com> Date: Fri, 22 Mar 2013 16:01:05 -0700 Message-ID: Subject: Re: [PATCH 7/7] ipc,sem: fine grained locking for semtimedop From: Michel Lespinasse To: Rik van Riel Cc: torvalds@linux-foundation.org, davidlohr.bueso@hp.com, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, hhuang@redhat.com, jason.low2@hp.com, lwoodman@redhat.com, chegu_vinod@hp.com, Rik van Riel Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2205 Lines: 60 Sorry for the late reply; I've been swamped and am behind on my upstream mail. On Wed, Mar 20, 2013 at 12:55 PM, Rik van Riel wrote: > +static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, > + int nsops) > +{ > + int locknum; > + if (nsops == 1 && !sma->complex_count) { > + struct sem *sem = sma->sem_base + sops->sem_num; > + > + /* Lock just the semaphore we are interested in. */ > + spin_lock(&sem->lock); > + > + /* > + * If sma->complex_count was set while we were spinning, > + * we may need to look at things we did not lock here. > + */ > + if (unlikely(sma->complex_count)) { > + spin_unlock(&sma->sem_perm.lock); I believe this should be spin_unlock(&sem->lock) instead ? > + goto lock_all; > + } > + locknum = sops->sem_num; > + } else { > + int i; > + /* Lock the sem_array, and all the semaphore locks */ > + lock_all: > + spin_lock(&sma->sem_perm.lock); > + for (i = 0; i < sma->sem_nsems; i++) { Do we have to lock every sem from the array instead of just the ones that are being operated on in sops ? (I'm not sure either way, as I don't fully understand the queueing of complex ops) If we want to keep the loop as is, then we may at least remove the sops argument to sem_lock() since we only care about nsops. > + struct sem *sem = sma->sem_base + i; > + spin_lock(&sem->lock); > + } > + locknum = -1; > + } > + return locknum; > +} That's all I have. Very nice test results BTW! Reviewed-by: Michel Lespinasse -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies. -- 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/