From: Colin Walters Subject: Re: [PATCH] nextfd(2) Date: Tue, 03 Apr 2012 15:21:13 -0400 Message-ID: <1333480873.10230.35.camel@lenny> References: <20120401125741.GA7484@p183.telecom.by> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Alexey Dobriyan , akpm@linux-foundation.org, viro@zeniv.linux.org.uk, torvalds@linux-foundation.org, drepper@gmail.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: KOSAKI Motohiro Return-path: Received: from out1-smtp.messagingengine.com ([66.111.4.25]:50663 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751413Ab2DCTVp (ORCPT ); Tue, 3 Apr 2012 15:21:45 -0400 Received: from compute2.internal (compute2.nyi.mail.srv.osa [10.202.2.42]) by gateway1.nyi.mail.srv.osa (Postfix) with ESMTP id 8321321843 for ; Tue, 3 Apr 2012 15:21:44 -0400 (EDT) In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 2012-04-02 at 16:17 -0700, KOSAKI Motohiro wrote: > we can only call async-signal-safe functions after fork() when multi threads and > opendir() call malloc() internally. > > As far as I know, OpenJDK has a such fork-readdir-exec code and it can > make deadlock > when spawnning a new process. Unfortunately Java language perfeter to > make a lot of threads rather than other language. > > This patch can solve such multi threaded case. > > offtopic, glibc malloc is a slightly clever. It reinitialize its > internal lock when fork by > using thread_atfork() hook. It mean glibc malloc can be used after > fork() and the > technique can avoid this issue. Yeah, a *lot* of code out there depends on this glibc malloc implementation detail. We uncovered our dependency on this in GNOME a while back while investigating getenv/setenv/fork and threads: https://bugzilla.gnome.org/show_bug.cgi?id=659326