X-Recipient: archive-cygwin@delorie.com DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:subject:to:references:from:message-id:date :mime-version:in-reply-to:content-type :content-transfer-encoding; q=dns; s=default; b=YxYrcLa/vJflewBC cechFsZoolblIS6f3HvgqvVfxerg9IgFSOK/jcTxY4Jtfgkxqd3p/PEQJkfq0XBg viULvcqGMuKNH2K0UkMEdO/mOBfkagZAh2JMnX/xMJwYgw8a35vxN0gH1v4a7rTt GC+r5PdR596KMmWEFtHcTMZWkcU= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:subject:to:references:from:message-id:date :mime-version:in-reply-to:content-type :content-transfer-encoding; s=default; bh=X5sRV/wG4+LiUfCz7kvxLL 5rcP0=; b=ZauG12Wg6/nrPvEmVa48QBaf3mhH/OmFoO0OOa9WUy6aoN+WatSDp4 EZG67NLHEYMdIJ/Ixq6mpLF6Jjj0AMvlJV/oYLXhOXdZf6eW+LgJFnvZNojQxAoy kwFWpIPd0yDMuNeaGxesjkDA2X7E65n5Wg93Aox6hqKtxay/UoTYc= Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.7 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY autolearn=no version=3.3.2 spammy=H*r:8.12.11, H*UA:Firefox, awaiting X-HELO: m0.truegem.net Subject: Re: long I/O delays when strace is running To: cygwin@cygwin.com References: <91DCAC3CB99C724EB365BB64677FBE7B16EBBD@MX204CL04.corp.emc.com> <46e39bce-9782-5c74-c196-35ee97ebbc64@pobox.com>

<58F9D314.2000100@maxrnd.com> <7d56e728-32a3-9179-b002-e83880e297d0@pobox.com> From: Mark Geisert Message-ID: <58FA83DB.3000209@maxrnd.com> Date: Fri, 21 Apr 2017 15:12:43 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0 SeaMonkey/2.40 MIME-Version: 1.0 In-Reply-To: <7d56e728-32a3-9179-b002-e83880e297d0@pobox.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Daniel Santos wrote: > Thanks for the help Mark. My current suspicion is that the _pinfo isn't getting > initialized when the process is exec-ed by strace, but I haven't proved that. I > added a dump() member function to _pinfo, but it crashes and I can't seem to > debug that in gdb (it makes a stacktrace file instead of letting me debug). So > the cygpid. shared object is there, but I'm suspecting that it's either all > zeros or just not fully initialized -- and this is for the pid of the strace > process. So for each strace process, there's a 2-3 second delay when trying to > read the process list. Re debugging strace itself, you may not realize that strace is not a Cygwin-native program. It's a Windows-native program. So debugging it with Cygwin gdb is problematic. I can tell you roughly how strace operates. It launches the target program with CreateProcess(), not with exec(). It acts as the debugger of the target in order to receive Windows DEBUG_EVENTs for things like DLL loads, thread creation, etc. etc. The Cygwin DLL in the target can tell when it's being run under strace and generates trace lines with OutputDebugString() calls that strace receives as DEBUG_EVENTs. strace then just outputs the trace line. strace does have to explicitly ContinueDebugEvent() on each DEBUG_EVENT it receives, and if there's some issue with that then the target program will remain suspended awaiting that continue. I've never seen an issue with this but it's another possible place to look, I suppose. Why strace appears to interact badly with /proc accesses, I have no idea. ..mark -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple