From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH 4/5] pidfd: add CLONE_WAIT_PID Date: Thu, 25 Jul 2019 13:25:03 +0200 Message-ID: <20190725112503.GG4707@redhat.com> References: <20190724144651.28272-1-christian@brauner.io> <20190724144651.28272-5-christian@brauner.io> <20190725103543.GF4707@redhat.com> <20190725104006.7myahvjtnbcgu3in@brauner.io> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190725104006.7myahvjtnbcgu3in@brauner.io> Sender: linux-kernel-owner@vger.kernel.org To: Christian Brauner Cc: linux-kernel@vger.kernel.org, arnd@arndb.de, ebiederm@xmission.com, keescook@chromium.org, joel@joelfernandes.org, tglx@linutronix.de, tj@kernel.org, dhowells@redhat.com, jannh@google.com, luto@kernel.org, akpm@linux-foundation.org, cyphar@cyphar.com, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, kernel-team@android.com, Ingo Molnar , Peter Zijlstra , linux-api@vger.kernel.org List-Id: linux-api@vger.kernel.org On 07/25, Christian Brauner wrote: > > On Thu, Jul 25, 2019 at 12:35:44PM +0200, Oleg Nesterov wrote: > > > > I have to admit this feature looks a bit exotic to me... > > It might look like it from the kernels perspective but from the feedback > on this when presenting on this userspace has real usecases for this. OK... but then perhaps we can make PF_WAIT_PID more flexible. Say, we can add the new WXXX wait option and change eligible_child() if ((p->flags & PF_WAIT_PID) && (wo->options & WXXX)) return 0; this way the parent can tell waitid() whether the PF_WAIT_PID tasks should be filtered or not. And if we do this we can even add PR_SET_WAIT_PID/PR_CLR_WAIT_PID instead of the new CLONE_ flag. Oleg.