Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933026AbaJXQU2 (ORCPT ); Fri, 24 Oct 2014 12:20:28 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:57616 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752680AbaJXQU0 (ORCPT ); Fri, 24 Oct 2014 12:20:26 -0400 Date: Fri, 24 Oct 2014 09:16:34 -0700 From: "Paul E. McKenney" To: Eric B Munson Cc: linux-kernel@vger.kernel.org Subject: Re: Commit 35ce7f29a breaks hibernation for XPS 13 Message-ID: <20141024161634.GR4977@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20141024160815.GA2968@akamai.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141024160815.GA2968@akamai.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14102416-0033-0000-0000-000000D50B71 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 24, 2014 at 12:08:15PM -0400, Eric B Munson wrote: > Paul, > > As of 3.18-rc1 I can no longer hibernate my Dell XPS-13. Bisect points > the finger at 35ce7f29a. A revert of that commit confirms, I can once > again hibernate my machine without it. > > When the hibernation fails I see this in dmesg: > [ 37.953313] PM: Syncing filesystems ... done. > [ 37.963694] Freezing user space processes ... (elapsed 0.001 seconds) done. > [ 37.965297] PM: Marking nosave pages: [mem 0x00000000-0x00000fff] > [ 37.965299] PM: Marking nosave pages: [mem 0x00058000-0x00058fff] > [ 37.965301] PM: Marking nosave pages: [mem 0x0009d000-0x000fffff] > [ 37.965304] PM: Marking nosave pages: [mem 0xc496a000-0xc4b6bfff] > [ 37.965315] PM: Marking nosave pages: [mem 0xdadb7000-0xdcffefff] > [ 37.965479] PM: Marking nosave pages: [mem 0xdd000000-0xffffffff] > [ 37.966000] PM: Basic memory bitmaps created > [ 37.966046] PM: Preallocating image memory... done (allocated 181989 pages) > [ 38.141524] PM: Allocated 727956 kbytes in 0.17 seconds (4282.09 MB/s) > [ 38.141525] Freezing remaining freezable tasks ... > [ 58.151863] Freezing of tasks failed after 20.004 seconds (0 tasks refusing to freeze, wq_busy=1): > [ 58.151894] > [ 58.151896] Restarting kernel threads ... done. > [ 58.181915] PM: Basic memory bitmaps freed > [ 58.181917] Restarting tasks ... done. > > > I am not sure what else I can provide that might be useful, but I did > see the thread on net-dev about this same commit. Please CC me on any > fixes and I will be happy to test. Thank you for the bug report! Does the following patch help? Thanx, Paul ------------------------------------------------------------------------ rcu: More on deadlock between CPU hotplug and expedited grace periods Commit dd56af42bd82 (rcu: Eliminate deadlock between CPU hotplug and expedited grace periods) was incomplete. Although it did eliminate deadlocks involving synchronize_sched_expedited()'s acquisition of cpu_hotplug.lock via get_online_cpus(), it did nothing about the similar deadlock involving acquisition of this same lock via put_online_cpus(). This deadlock became apparent with testing involving hibernation. This commit therefore changes put_online_cpus() acquisition of this lock to be conditional, and increments a new cpu_hotplug.puts_pending field in case of acquisition failure. Then cpu_hotplug_begin() checks for this new field being non-zero, and applies any changes to cpu_hotplug.refcount. Reported-by: Jiri Kosina Signed-off-by: Paul E. McKenney Tested-by: Jiri Kosina Tested-by: Borislav Petkov diff --git a/kernel/cpu.c b/kernel/cpu.c index 356450f09c1f..90a3d017b90c 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -64,6 +64,8 @@ static struct { * an ongoing cpu hotplug operation. */ int refcount; + /* And allows lockless put_online_cpus(). */ + atomic_t puts_pending; #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; @@ -113,7 +115,11 @@ void put_online_cpus(void) { if (cpu_hotplug.active_writer == current) return; - mutex_lock(&cpu_hotplug.lock); + if (!mutex_trylock(&cpu_hotplug.lock)) { + atomic_inc(&cpu_hotplug.puts_pending); + cpuhp_lock_release(); + return; + } if (WARN_ON(!cpu_hotplug.refcount)) cpu_hotplug.refcount++; /* try to fix things up */ @@ -155,6 +161,12 @@ void cpu_hotplug_begin(void) cpuhp_lock_acquire(); for (;;) { mutex_lock(&cpu_hotplug.lock); + if (atomic_read(&cpu_hotplug.puts_pending)) { + int delta; + + delta = atomic_xchg(&cpu_hotplug.puts_pending, 0); + cpu_hotplug.refcount -= delta; + } if (likely(!cpu_hotplug.refcount)) break; __set_current_state(TASK_UNINTERRUPTIBLE); -- 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/