From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932525AbZKBWaZ (ORCPT ); Mon, 2 Nov 2009 17:30:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932408AbZKBWaY (ORCPT ); Mon, 2 Nov 2009 17:30:24 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:40857 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932387AbZKBWaY (ORCPT ); Mon, 2 Nov 2009 17:30:24 -0500 Date: Mon, 2 Nov 2009 14:30:28 -0800 From: "Paul E. McKenney" To: Tetsuo Handa Cc: nhorman@tuxdriver.com, linux-kernel@vger.kernel.org Subject: Re: [2.6.32-rc5-git5] synchronize_sched() inside spin_lock()? Message-ID: <20091102223028.GB6795@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <200911022100.EAC21893.OMFFJVOSOQHLtF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200911022100.EAC21893.OMFFJVOSOQHLtF@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 02, 2009 at 09:00:06PM +0900, Tetsuo Handa wrote: > Commit: 4ea7e38696c7e798c47ebbecadfd392f23f814f9 > > tracepoint_synchronize_unregister() calls synchronize_sched(), but it is > between spin_lock() and spin_unlock(). Is it OK? Calling synchronize_sched() while holding a spinlock would indeed be very bad, but the code below seems to instead be invoking call_rcu(), which is no problem. Or am I missing something here? Thanx, Paul > static int set_all_monitor_traces(int state) > { > int rc = 0; > struct dm_hw_stat_delta *new_stat = NULL; > struct dm_hw_stat_delta *temp; > > spin_lock(&trace_state_lock); > > switch (state) { > case TRACE_ON: > rc |= register_trace_kfree_skb(trace_kfree_skb_hit); > rc |= register_trace_napi_poll(trace_napi_poll_hit); > break; > case TRACE_OFF: > rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit); > rc |= unregister_trace_napi_poll(trace_napi_poll_hit); > > tracepoint_synchronize_unregister(); > > /* > * Clean the device list > */ > list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) { > if (new_stat->dev == NULL) { > list_del_rcu(&new_stat->list); > call_rcu(&new_stat->rcu, free_dm_hw_stat); > } > } > break; > default: > rc = 1; > break; > } > > if (!rc) > trace_state = state; > > spin_unlock(&trace_state_lock); > > if (rc) > return -EINPROGRESS; > return rc; > } > -- > 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/