From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thiago Macieira Subject: Re: [PATCH v2 0/7] CLONE_FD: Task exit notification via file descriptor Date: Mon, 16 Mar 2015 15:14:14 -0700 Message-ID: <2381173.VxaIO6vGG3@tjmaciei-mobl4> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Kees Cook Cc: Josh Triplett , Al Viro , Andrew Morton , Andy Lutomirski , Ingo Molnar , Oleg Nesterov , "Paul E. McKenney" , "H. Peter Anvin" , Rik van Riel , Thomas Gleixner , Michael Kerrisk , LKML , Linux API , "linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" List-Id: linux-api@vger.kernel.org On Monday 16 March 2015 14:44:20 Kees Cook wrote: > > O_CLOEXEC > > Set the close-on-exec flag on the new file > >descriptor. See the description of the O_CLOEXEC flag in open(2) for > >reasons why this may be useful. > > This begs the question: what happens when all CLONE_FD fds for a > process are closed? Will the parent get SIGCHLD instead, will it > auto-reap, or will it be un-wait-able (I assume not this...) Depends on CLONE_AUTOREAP. If it's on, then no one gets SIGCHLD, no one can wait() on it and the process autoreaps itself. If it's no active, then the old rules apply: parent gets SIGCHILD and can wait(). If the parent exited first, then the child gets reparented to init, which can do the wait(). A child without CLONE_AUTOREAP should be wait()able. If it gets wait()ed before the clonefd is read, the clonefd() will return a 0 read. If it gets read before wait, then wait() reaps another child or returns -ECHILD. That's no different than two threads doing simultaneous wait() on the same child. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center