Date: Tue, 17 Nov 2009 20:47:32 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: lynx.ripe@gmail.com Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, edwin@FreeBSD.org Subject: Re: svn commit: r194783 - head/lib/libc/stdtime Message-ID: <20091117.204732.1339398361.imp@bsdimp.com> In-Reply-To: <4B01E548.7040708@gmail.com> References: <4B01E548.7040708@gmail.com>
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In message: <4B01E548.7040708@gmail.com> Dmitry Pryanishnikov <lynx.ripe@gmail.com> writes: : : Hello! : : > Author: edwin : > Date: Tue Jun 23 22:28:44 2009 : > New Revision: 194783 : > URL: http://svn.freebsd.org/changeset/base/194783 : > : > Log: : > Remove duplicate if-statement on gmt_is_set in gmtsub(). : > : > MFC after: 1 week : > : > Modified: : > head/lib/libc/stdtime/localtime.c : > : > Modified: head/lib/libc/stdtime/localtime.c : > ============================================================================== : > --- head/lib/libc/stdtime/localtime.c Tue Jun 23 22:22:20 2009 (r194782) : > +++ head/lib/libc/stdtime/localtime.c Tue Jun 23 22:28:44 2009 (r194783) : > @@ -1472,18 +1472,16 @@ struct tm * const tmp; : > { : > register struct tm * result; : > : > + _MUTEX_LOCK(&gmt_mutex); : > if (!gmt_is_set) { : > - _MUTEX_LOCK(&gmt_mutex); : > - if (!gmt_is_set) { : : This change looks like a (small?) pessimization to me: before it, : _MUTEX_LOCK/_MUTEX_UNLOCK pair would be skipped for the case gmt_is_set : == TRUE (all invocations except the first one), now it won't. I'm not : sure whether this is critical here though... I think this is a big pessimization. gmt_is_set code only needs to execute once, and this code was designed to be lockless once gmt_is_set was set... Warner
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