From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [patch 050/160] prctl: add PR_SET_PROCTITLE_AREA option for prctl() Date: Sun, 7 Mar 2010 20:28:26 +0100 Message-ID: <20100307192826.GA18616@redhat.com> References: <201003052142.o25Lgbpg029522@imap1.linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Linus Torvalds Cc: akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org, bdonlan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, drepper-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, tss-X3B1VOXEql0@public.gmane.org, xiyou.wangcong-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org List-Id: linux-api@vger.kernel.org On 03/06, Linus Torvalds wrote: > > On Fri, 5 Mar 2010, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org wrote: > > > > This patch makes it possible for userspace to implement setproctitle() > > cleanly. It adds a new PR_SET_PROCTITLE_AREA option for prctl(), which > > updates task's mm_struct->arg_start and arg_end to the given area. > > This looks overly complicated. Why do you change the whole locking rules, > instead of protecting _only_ the "arg_start/arg_end" case? > > The thing is, there's no reason to hold the mmap_sem over the whole thing, > and I don't think this is important enough to be a valid reason for > exposing a whole new "locked" access variant, when a simple "protect just > the arg_start/end" would handle it. It was me who suggested to re-use mm->mmap_sem instead of adding the new lock, but looking at this patch again I do not understand the reason this lock should be held throughout in proc_pid_cmdline(). If there is no such a reason, then the new access_process_vm_locked (cough, also suggested by me ;) is not needed. Oleg.