Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753254AbZJUJdm (ORCPT ); Wed, 21 Oct 2009 05:33:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753193AbZJUJdl (ORCPT ); Wed, 21 Oct 2009 05:33:41 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:34566 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753088AbZJUJdl (ORCPT ); Wed, 21 Oct 2009 05:33:41 -0400 Date: Wed, 21 Oct 2009 11:33:38 +0200 From: Pavel Machek To: Arnd Bergmann Cc: Sukadev Bhattiprolu , linux-kernel@vger.kernel.org, Oren Laadan , serue@us.ibm.com, "Eric W. Biederman" , Alexey Dobriyan , Pavel Emelyanov , Andrew Morton , torvalds@linux-foundation.org, mikew@google.com, mingo@elte.hu, hpa@zytor.com, Nathan Lynch , peterz@infradead.org, Louis.Rilling@kerlabs.com, roland@redhat.com, kosaki.motohiro@jp.fujitsu.com, randy.dunlap@oracle.com, linux-api@vger.kernel.org, Containers , sukadev@us.ibm.com Subject: Re: [RFC][v8][PATCH 10/10]: Document clone3() syscall Message-ID: <20091021093338.GA11670@elf.ucw.cz> References: <20091013044925.GA28181@us.ibm.com> <20091013045556.GJ28435@us.ibm.com> <20091019213636.GB1482@ucw.cz> <200910211037.38413.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200910211037.38413.arnd@arndb.de> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2240 Lines: 65 On Wed 2009-10-21 10:37:38, Arnd Bergmann wrote: > > > > > +struct clone_struct { > > > + u64 flags; > > > + u64 child_stack; > > > > u64 seems wrong on 32 bit platforms. ulong? > > That would make it incompatible between 64 bit kernels and > 32 bit user space, requiring a wrapper. Better leave it at u64. Ok. > > > + If a pid in the @pids list is 0, the kernel will assign the next > > > + available pid in the pid namespace, for the process. > > > + > > > + If a pid in the @pids list is non-zero, the kernel tries to assign > > > + the specified pid in that namespace. If that pid is already in use > > > + by another process, the system call fails with -EBUSY. > > ... > > > + On failure, clone3() returns -1 and sets 'errno' to one of following > > > + values (the child process is not created). > > > > Inconsistent with above. Syscalls really return -ERRCODE, errno is > > glibc magic. > > Quite the opposite is true. Well, it is still inconsistent. Half the docs talks -ERRCODE, half talks -1/errno=ERRCODE. > > > + pid_t pids[] = { 77, 99 }; > > > + struct clone_struct cs; > > > + > > > + cs.flags = (u64) SIGCHLD; > > > + cs.child_stack = (u64) setup_child_stack(); > > > + cs.nr_pids = 2; > > > + cs.parent_tid = 0LL; > > > + cs.child_tid = 0LL; > > > + > > > + rc = syscall(__NR_clone3, &cs, pids); > > > > Hmm, is there reason why pids are not at the end of struct > > clone_struct? Passing most parameters in special structure, then pids > > separately is strange... > > I suggested doing that, it's a lot easier to handle fixed length data > structures than an array at the end. You could still put the something * pids at the end of (fixed length) structure. (Not that I agree with the argument, pid array is variable-length, anyway, and inlining it at the end of structure should not make code more complex). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/