From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756936Ab3EXRpY (ORCPT ); Fri, 24 May 2013 13:45:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16590 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753525Ab3EXRpX (ORCPT ); Fri, 24 May 2013 13:45:23 -0400 Date: Fri, 24 May 2013 19:41:27 +0200 From: Oleg Nesterov To: Al Viro , Andrew Morton Cc: Guy Streeter , Eric Paris , David Woodhouse , linux-kernel@vger.kernel.org Subject: Re: [PATCH] audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE Message-ID: <20130524174127.GA17186@redhat.com> References: <20130524173925.GA17177@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130524173925.GA17177@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/24, Oleg Nesterov wrote: > > audit_log_start() does wait_for_auditd() in a loop until > audit_backlog_wait_time passes or audit_skb_queue has a room. > > If signal_pending() is true this becomes a busy-wait loop, > schedule() in TASK_INTERRUPTIBLE won't block. And the code looks strange imho. I think it should be cleanuped, something like below. But I do not know how can I test this change. Oleg. --- x/kernel/audit.c +++ x/kernel/audit.c @@ -1053,18 +1053,19 @@ static inline void audit_get_stamp(struc /* * Wait for auditd to drain the queue a little */ -static void wait_for_auditd(unsigned long sleep_time) +static bool wait_for_auditd(gfp_t gfp_mask) { - DECLARE_WAITQUEUE(wait, current); - set_current_state(TASK_INTERRUPTIBLE); - add_wait_queue(&audit_backlog_wait, &wait); - - if (audit_backlog_limit && - skb_queue_len(&audit_skb_queue) > audit_backlog_limit) - schedule_timeout(sleep_time); + bool can_wait = gfp_mask & __GFP_WAIT; + int reserve = can_wait ? 0 : 5; - __set_current_state(TASK_RUNNING); - remove_wait_queue(&audit_backlog_wait, &wait); + if (!audit_backlog_limit || + skb_queue_len(&audit_skb_queue) <= audit_backlog_limit + reserve) + return true; + + return can_wait && wait_event_timeout(audit_backlog_wait, + !audit_backlog_limit || + skb_queue_len(&audit_skb_queue) <= audit_backlog_limit, + audit_backlog_wait_time); } /* Obtain an audit buffer. This routine does locking to obtain the @@ -1095,8 +1096,6 @@ struct audit_buffer *audit_log_start(str struct audit_buffer *ab = NULL; struct timespec t; unsigned int uninitialized_var(serial); - int reserve; - unsigned long timeout_start = jiffies; if (audit_initialized != AUDIT_INITIALIZED) return NULL; @@ -1104,23 +1103,7 @@ struct audit_buffer *audit_log_start(str if (unlikely(audit_filter_type(type))) return NULL; - if (gfp_mask & __GFP_WAIT) - reserve = 0; - else - reserve = 5; /* Allow atomic callers to go up to five - entries over the normal backlog limit */ - - while (audit_backlog_limit - && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) { - if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time) { - unsigned long sleep_time; - - sleep_time = timeout_start + audit_backlog_wait_time - - jiffies; - if ((long)sleep_time > 0) - wait_for_auditd(sleep_time); - continue; - } + if (!wait_for_auditd(gfp_mask)) { if (audit_rate_check() && printk_ratelimit()) printk(KERN_WARNING "audit: audit_backlog=%d > "