From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id Fa8qIt9712DSWQAAWB0awg (envelope-from ) for ; Sat, 26 Jun 2021 15:11:27 -0400 Received: by simark.ca (Postfix, from userid 112) id 843271F1F2; Sat, 26 Jun 2021 15:11:27 -0400 (EDT) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-0.7 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,RDNS_DYNAMIC,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id DBABE1E01F for ; Sat, 26 Jun 2021 15:11:26 -0400 (EDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 42EB7383981F for ; Sat, 26 Jun 2021 19:11:26 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 42EB7383981F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1624734686; bh=Ehu54px/wM/TQKTZrJxo+PQWyqkE8NoTEVl2Bl8AUiA=; h=Subject:To:References:Date:In-Reply-To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=gxyYREIeAR4zFNd+D3Fq2dFdQZ6Ha6NfSFX5YJuegAteW9Dpl9LchqWo4zQqzdVq1 6VXDFtMVuvDpwH/kfzQIeeXzXg6ybFDlSY5J7Oa5B4zOva+NwhMgtlTCNO+1gPSUr4 9lRpNmVt8M+X0qHxRswBEeLCugbDsRrouSFoH53w= Received: from smtp.polymtl.ca (smtp.polymtl.ca [132.207.4.11]) by sourceware.org (Postfix) with ESMTPS id 29EE5385042B for ; Sat, 26 Jun 2021 19:11:07 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 29EE5385042B Received: from simark.ca (simark.ca [158.69.221.121]) (authenticated bits=0) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id 15QJAw6n004385 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 26 Jun 2021 15:11:03 -0400 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp.polymtl.ca 15QJAw6n004385 Received: from [10.0.0.11] (192-222-157-6.qc.cable.ebox.net [192.222.157.6]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id 130241E01F; Sat, 26 Jun 2021 15:10:58 -0400 (EDT) Subject: Re: [PATCH 3/4] scoped_ignore_signal: Use sigprocmask+sigtimedwait instead of signal To: John Baldwin , Pedro Alves , gdb-patches@sourceware.org References: <20210615111429.1879286-1-pedro@palves.net> <20210615111429.1879286-4-pedro@palves.net> <6dca033a-1b6f-05df-8dd0-e1cc2c7d85d2@FreeBSD.org> Message-ID: <3e2f4788-84c3-1ef3-e346-7630a6e550bb@polymtl.ca> Date: Sat, 26 Jun 2021 15:10:57 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <6dca033a-1b6f-05df-8dd0-e1cc2c7d85d2@FreeBSD.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Poly-FromMTA: (simark.ca [158.69.221.121]) at Sat, 26 Jun 2021 19:10:58 +0000 X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Simon Marchi via Gdb-patches Reply-To: Simon Marchi Errors-To: gdb-patches-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb-patches" On 2021-06-26 9:41 a.m., John Baldwin wrote: > On 6/26/21 5:35 AM, Simon Marchi via Gdb-patches wrote: >> On 2021-06-15 7:14 a.m., Pedro Alves wrote: >>> The problem with using signal(...) to temporarily ignore a signal, is >>> that that changes the the signal disposition for the whole process. >>> If multiple threads do it at the same time, you have a race. >>> >>> Fix this by using sigprocmask + sigtimedwait to implement the ignoring >>> instead, if available, which I think probably means everywhere except >>> Windows nowadays. This way, we only change the signal mask for the >>> current thread, so there's no race. >> >> I tried to build on macOS today and got: >> >> >> CXX compile/compile.o >> In file included from /Users/smarchi/src/binutils-gdb/gdb/compile/compile.c:46: >> /Users/smarchi/src/binutils-gdb/gdb/../gdbsupport/scoped_ignore_signal.h:69:4: error: use of undeclared identifier 'sigtimedwait' >> sigtimedwait (&set, nullptr, &zero_timeout); >> ^ >> >> I didn't have time to dig yet. > > It looks like macOS doesn't implement either sigtimedwait() or sigwaitinfo() > which are part of POSIX from 1996 (*sigh*); however, macOS does provide > sigpending() and sigwait(), so perhaps we can do something like: > > if (ConsumePending) > { > #ifdef HAVE_SIGTIMEDWAIT > const timespec zero_timeout = {}; > > sigtimedwait (&set, nullptr, &zero_timeout); > #else > sigset_t pending; > > sigpending (&pending); > if (sigismember (&pending, SIG)) SIG -> Sig > sigwait (&set, nullptr); > #endif > } > > (Ironically, sigwait() was added to POSIX in the same version of the spec as > sigtimedwait().) > Thanks. At least that change fixes that particular build issue, but I can't tell if it has the correct behavior though (I haven't looked at what sigtimedwait / sigwait do yet...). Simon