From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Sixt Subject: Re: [RFT PATCH 2/2] win32: optimize pthread_cond_broadcast Date: Tue, 08 Jun 2010 18:30:13 +0200 Message-ID: <4C0E7015.8030504@viscovery.net> References: <1275917892-16437-1-git-send-email-bonzini@gnu.org> <1275917892-16437-3-git-send-email-bonzini@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: git@vger.kernel.org To: Paolo Bonzini X-From: git-owner@vger.kernel.org Tue Jun 08 18:30:23 2010 connect(): No such file or directory Return-path: Envelope-to: gcvg-git-2@lo.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1OM1h0-0006Al-IL for gcvg-git-2@lo.gmane.org; Tue, 08 Jun 2010 18:30:22 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755391Ab0FHQaP (ORCPT ); Tue, 8 Jun 2010 12:30:15 -0400 Received: from bsmtp4.bon.at ([195.3.86.186]:20372 "EHLO bsmtp.bon.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755187Ab0FHQaO (ORCPT ); Tue, 8 Jun 2010 12:30:14 -0400 Received: from [192.168.0.200] (unknown [93.83.142.38]) by bsmtp.bon.at (Postfix) with ESMTP id 762482C4020; Tue, 8 Jun 2010 18:30:13 +0200 (CEST) User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 In-Reply-To: <1275917892-16437-3-git-send-email-bonzini@gnu.org> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Am 07.06.2010 15:38, schrieb Paolo Bonzini: > @@ -172,9 +172,10 @@ int pthread_cond_broadcast(pthread_cond_t *cond) > * As in pthread_cond_signal, access to cond->waiters and > * cond->was_broadcast is locked via the external mutex. > */ > - > - if ((cond->was_broadcast = cond->waiters> 0)) { > + if (cond->waiters> 0) { > BOOLEAN result; > + cond->was_broadcast = cond->waiters> 1; > + It is possible that you set was_broadcast to 1 here, while another thread still sees was_broadcast == 0 in cond_wait. As a consequence, this thread WaitsForSingleObject(), which will never arrive because the other thread does not call SetEvent(). But this is more a problem of your first patch, not of this one, so you better fix the first one first before you go further into this one. That said, as long as this series buys performance only at the expense of clarity, I'm rather opposed to it because we do not call cond_wait and cond_broadcast in time-critical paths. -- Hannes