From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Philipp Stephani Newsgroups: gmane.emacs.devel Subject: Re: scratch/sigchld-fd 8f0ce42 1/2: Fix deadlock when receiving SIGCHLD during 'pselect'. Date: Tue, 19 Jan 2021 21:58:26 +0100 Message-ID: References: <20210116184947.2105.45267@vcs0.savannah.gnu.org> <20210116184949.3C17C211A5@vcs0.savannah.gnu.org> <834kjd7yk5.fsf@gnu.org> <83turc7n93.fsf@gnu.org> <871regr6x5.fsf@igel.home> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="35240"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Eli Zaretskii , Philipp Stephani , Emacs developers To: Andreas Schwab Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Jan 19 22:26:51 2021 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1l1yWY-00091M-Oc for ged-emacs-devel@m.gmane-mx.org; Tue, 19 Jan 2021 22:26:50 +0100 Original-Received: from localhost ([::1]:45700 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l1yWX-0003Q8-QW for ged-emacs-devel@m.gmane-mx.org; Tue, 19 Jan 2021 16:26:49 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:32792) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l1y5K-0000LS-RL for emacs-devel@gnu.org; Tue, 19 Jan 2021 15:58:42 -0500 Original-Received: from mail-lf1-x131.google.com ([2a00:1450:4864:20::131]:36406) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1l1y5J-00049f-7C for emacs-devel@gnu.org; Tue, 19 Jan 2021 15:58:42 -0500 Original-Received: by mail-lf1-x131.google.com with SMTP id o13so31094388lfr.3 for ; Tue, 19 Jan 2021 12:58:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=q0/G2A/SRWTACIPldy0Rh7qW/k2HhmtX2jpwitO7US0=; b=ULIyh3jE6Z2umz3U9g8eKyZT2kUFCEEJ8mbUqJ/hlWMf0tKgm+WNUXflMSABgXF3sj qwHM6oN78lBJ++gTr2iUL+96Yionat/BNhq8EWNQXwymsD0CB/bP13DSWnaFd9gGF5Gb xEc32qaGW7CnCLnXYRu9F4K3GIqZE+JBmy8pAuDdPXrCx6G3+mEsexge9xTZaXdAbHoW 5AnAruyachTvOwHe09lPUejCONp4XORPFOnKKlQ8xu3/BR0s6aqBC0XXULP/XCzQP/+E qk8Po8HLtHPXgJofa8aGFJgtLwCghbklg6ETfforuz0XuMcm1cvPTOkC/K/PK1X7l1Oy 9MBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=q0/G2A/SRWTACIPldy0Rh7qW/k2HhmtX2jpwitO7US0=; b=mQi57Muwa2aqWgEA2bd5btJr1l//TIa+zXPawNPuZOiz1gn1ENN9yyJkSD2YQ5fIxP o+eTtn8Mqh0wxRGzIMKd+Fmq+qkbiB3ul0CtcLFs2X55ze++XWpoJ7ONV1xcj/PZ7srI 0VtSVe4fqJgLga4vbvVv+UDaUELpkUVY8szD3RXVcnIC+XKMwM8AZJ6Ud6d68ljTYUmJ bKVxxkrUJcJBCDNC9TYOeHikLVWxetbQG5xzf1FGKt1HznjqyFI1rKFXvERtMHibWiP4 UTHFaLKS6QwA6ElDwA/vep62+6Qk2ikOQT4CN0qg2P6YUTlDJWwSBCiImZCE0IWzZele PjEQ== X-Gm-Message-State: AOAM5308m3GMIz2YR23eJt9bNt1V60kVC0Ol1wuQeYhTsOY4nqodrPaB XUst+BRpc8TQ3MWAKtdnN/hbHWH2+Elv4hUg1nv2HA== X-Google-Smtp-Source: ABdhPJy6pfbHOW0TdvGaRGLCLbPyIvwQUtw761u6LzD2TeHOS+VH5ltM8WdkDR1gscft0kUAYlpvMw+edOYza+4oY2g= X-Received: by 2002:a19:500a:: with SMTP id e10mr2726040lfb.227.1611089917540; Tue, 19 Jan 2021 12:58:37 -0800 (PST) In-Reply-To: <871regr6x5.fsf@igel.home> Received-SPF: pass client-ip=2a00:1450:4864:20::131; envelope-from=phst@google.com; helo=mail-lf1-x131.google.com X-Spam_score_int: -175 X-Spam_score: -17.6 X-Spam_bar: ----------------- X-Spam_report: (-17.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, ENV_AND_HDR_SPF_MATCH=-0.5, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5, USER_IN_DEF_SPF_WL=-7.5 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:263189 Archived-At: Am Di., 19. Jan. 2021 um 21:46 Uhr schrieb Andreas Schwab : > > On Jan 19 2021, Eli Zaretskii wrote: > > > I'd be happier if we had some direct evidence to these effects. I'd > > also be surprised to hear that pselect doesn't return with EINTR when > > SIGCHLD comes in. It is more likely that SIGCHLD is delivered before > > we call pselect, but if that is the case, we should be able to > > reliably detect that, I think. > > If you want reliable detection of SIGCHLD, you need to block the signal > around pselect and let pselect unblock it, atomically. Right. It looks like we're not doing that because we want to support systems that don't have pselect (and it's gnulib emulation can't be race-free).