Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753696Ab1FOTIh (ORCPT ); Wed, 15 Jun 2011 15:08:37 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:43271 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752248Ab1FOTIf (ORCPT ); Wed, 15 Jun 2011 15:08:35 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Oleg Nesterov Cc: Greg Kurz , akpm@linux-foundation.org, containers@lists.osdl.org, linux-kernel@vger.kernel.org, serge@hallyn.com, daniel.lezcano@free.fr, xemul@openvz.org References: <20110615145527.4016.70157.stgit@bahia.local> <20110615184625.GA15573@redhat.com> Date: Wed, 15 Jun 2011 12:08:23 -0700 In-Reply-To: <20110615184625.GA15573@redhat.com> (Oleg Nesterov's message of "Wed, 15 Jun 2011 20:46:25 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=98.207.153.68;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/Ve5f0JnfMVYuVc1cpAUuU1k8WfxdtLlM= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Oleg Nesterov X-Spam-Relay-Country: Subject: Re: [PATCH] Introduce ActivePid: in /proc/self/status (v2, was Vpid:) X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1136 Lines: 32 Oleg Nesterov writes: > On 06/15, Greg Kurz wrote: >> >> @@ -176,6 +177,17 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, >> if (tracer) >> tpid = task_pid_nr_ns(tracer, ns); >> } >> + actpid = 0; >> + sighand = rcu_dereference(p->sighand); >> + if (sighand) { >> + struct pid_namespace *pid_ns; >> + unsigned long flags; >> + spin_lock_irqsave(&sighand->siglock, flags); > > Well. This is not exactly right. We have lock_task_sighand() for this. > > But. Why do you need ->siglock? Why rcu_read_lock() is not enough? > > Hmm. You don't even need pid_ns afaics, you could simply look at > pid->numbers[pid->level]. I got this moving in that direction, but I admit I probably didn't look close enough. I just remember it is always tricky when accessing a process and dealing with races with things like unhash_process(). Eric -- 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/