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Date: Tue, 24 Jan 2012 20:57:49 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: paulmck@...ux.vnet.ibm.com
Cc: Ingo Molnar <mingo@...e.hu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Frédéric Weisbecker <fweisbec@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] RCU changes for v3.3
Le mardi 24 janvier 2012 à 11:41 -0800, Paul E. McKenney a écrit :
> Ah, I see... I need to find one of trace_power_start(),
> trace_power_frequency(), or trace_power_end(). I would have to guess
> that this is either the trace_power_start() or the trace_power_end()
> called from drivers/cpuidle/cpuidle.c lines 97 and 102. Those are
> within cpuidle_idle_call(), which are called from cpu_idle() in
> arch/x86/kernel/process_32.c and arch/x86/kernel/process_64.c, so this
> sounds plausible.
>
> And they are indeed busted -- RCU believes the CPU is idle at the point
> that cpuidle_idle_call() is invoked.
>
> A hacky patch is below. Here are some of my concerns with it:
>
> 1. Is there a configuration in which the scheduler clock gets
> turned off, but in which cpuidle_idle_call() always returns
> zero? If so, we either really need RCU to consider the entire
> inner loop to be idle (thus needing to snapshot the value of
> cpuidle_idle_call() in the outer loop) or we need explicit calls
> to rcu_sched_qs() and friends.
>
> Yes, we could momentarily exit RCU idleness mode, but I would
> need to think that one through...
>
> 2. I am not totally confident that I have the order of operations
> surrounding the call to pm_idle() correct.
>
> 3. This only addresses x86, and it looks like a few other architectures
> have this same problem.
>
> 4. Probably other things that I haven't thought of.
>
> That said, the patch does seem to compile, at least on my 32-bit
> laptop...
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> idle: Avoid using RCU when RCU thinks the CPU is idle
>
> The x86 idle loops invoke cpuidle_idle_call() which uses tracing
> which uses RCU. Unfortunately, these idle loops have already
> told RCU to ignore this CPU when they call it. This patch hacks
> the idle loops to avoid this problem, but probably causing several
> other problems in the process.
>
> Not-yet-signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
Hi Paul
Just tested it on my x86_64 machine, but warnings are still here
Thanks !
[ 61.111559]
[ 61.111563] ===============================
[ 61.111565] [ INFO: suspicious RCU usage. ]
[ 61.111567] 3.3.0-rc1+ #572 Not tainted
[ 61.111569] -------------------------------
[ 61.111571] include/trace/events/power.h:102 suspicious rcu_dereference_check() usage!
[ 61.111573]
[ 61.111574] other info that might help us debug this:
[ 61.111575]
[ 61.111577]
[ 61.111577] rcu_scheduler_active = 1, debug_locks = 1
[ 61.111579] RCU used illegally from extended quiescent state!
[ 61.111582] no locks held by swapper/0/0.
[ 61.111583]
[ 61.111584] stack backtrace:
[ 61.111587] Pid: 0, comm: swapper/0 Not tainted 3.3.0-rc1+ #572
[ 61.111589] Call Trace:
[ 61.111598] [<ffffffff810949ba>] lockdep_rcu_suspicious+0xca/0xf0
[ 61.111604] [<ffffffff8100abb9>] mwait_idle+0x499/0x4c0
[ 61.111609] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.111615] [<ffffffff8174f49f>] rest_init+0x133/0x144
[ 61.111618] [<ffffffff8174f3e5>] ? rest_init+0x79/0x144
[ 61.111623] [<ffffffff81cc2b51>] start_kernel+0x35b/0x366
[ 61.111627] [<ffffffff81cc2321>] x86_64_start_reservations+0x131/0x135
[ 61.111631] [<ffffffff81cc2415>] x86_64_start_kernel+0xf0/0xf7
[ 61.111743] ------------[ cut here ]------------
[ 61.111750] WARNING: at include/linux/rcupdate.h:242 __perf_event_overflow+0x27c/0x2c0()
[ 61.111754] Hardware name: ProLiant BL460c G6
[ 61.111756] Modules linked in: ipmi_devintf nfsd exportfs hpilo ipmi_si bnx2x crc32c libcrc32c mdio [last unloaded: scsi_wait_scan]
[ 61.111770] Pid: 0, comm: swapper/0 Not tainted 3.3.0-rc1+ #572
[ 61.111772] Call Trace:
[ 61.111777] [<ffffffff81038eaf>] warn_slowpath_common+0x7f/0xc0
[ 61.111781] [<ffffffff81038f0a>] warn_slowpath_null+0x1a/0x20
[ 61.111784] [<ffffffff810f8ebc>] __perf_event_overflow+0x27c/0x2c0
[ 61.111788] [<ffffffff817711ae>] ? printk+0x41/0x43
[ 61.111794] [<ffffffff810a1f86>] ? __module_text_address+0x16/0x80
[ 61.111798] [<ffffffff810f8fa9>] perf_swevent_overflow+0xa9/0xc0
[ 61.111801] [<ffffffff810f902f>] perf_swevent_event+0x6f/0x90
[ 61.111804] [<ffffffff810f90c6>] perf_tp_event+0x76/0xf0
[ 61.111809] [<ffffffff810f14ce>] perf_trace_power+0xbe/0xe0
[ 61.111812] [<ffffffff8100ab2f>] ? mwait_idle+0x40f/0x4c0
[ 61.111815] [<ffffffff8100ab2f>] mwait_idle+0x40f/0x4c0
[ 61.111819] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.111822] [<ffffffff8174f49f>] rest_init+0x133/0x144
[ 61.111825] [<ffffffff8174f3e5>] ? rest_init+0x79/0x144
[ 61.111828] [<ffffffff81cc2b51>] start_kernel+0x35b/0x366
[ 61.111831] [<ffffffff81cc2321>] x86_64_start_reservations+0x131/0x135
[ 61.111834] [<ffffffff81cc2415>] x86_64_start_kernel+0xf0/0xf7
[ 61.111837] ---[ end trace 18a36211154afbbb ]---
[ 61.111839] ------------[ cut here ]------------
[ 61.111843] WARNING: at include/linux/rcupdate.h:242 perf_output_begin+0x2f6/0x330()
[ 61.111845] Hardware name: ProLiant BL460c G6
[ 61.111848] Modules linked in: ipmi_devintf nfsd exportfs hpilo ipmi_si bnx2x crc32c libcrc32c mdio [last unloaded: scsi_wait_scan]
[ 61.111859] Pid: 0, comm: swapper/0 Tainted: G W 3.3.0-rc1+ #572
[ 61.111861] Call Trace:
[ 61.111864] [<ffffffff81038eaf>] warn_slowpath_common+0x7f/0xc0
[ 61.111868] [<ffffffff81038f0a>] warn_slowpath_null+0x1a/0x20
[ 61.111871] [<ffffffff810fc286>] perf_output_begin+0x2f6/0x330
[ 61.111875] [<ffffffff81076975>] ? sched_clock_cpu+0xc5/0x120
[ 61.111879] [<ffffffff8109371d>] ? trace_hardirqs_off+0xd/0x10
[ 61.111882] [<ffffffff81076a1f>] ? local_clock+0x4f/0x60
[ 61.111886] [<ffffffff810f21cd>] ? __perf_event_header__init_id+0xad/0xf0
[ 61.111889] [<ffffffff810f8b93>] ? perf_prepare_sample+0x63/0x110
[ 61.111892] [<ffffffff810f8dcd>] __perf_event_overflow+0x18d/0x2c0
[ 61.111895] [<ffffffff810f8d85>] ? __perf_event_overflow+0x145/0x2c0
[ 61.111898] [<ffffffff817711ae>] ? printk+0x41/0x43
[ 61.111901] [<ffffffff810f8fa9>] perf_swevent_overflow+0xa9/0xc0
[ 61.111904] [<ffffffff810f902f>] perf_swevent_event+0x6f/0x90
[ 61.111907] [<ffffffff810f90c6>] perf_tp_event+0x76/0xf0
[ 61.111911] [<ffffffff810f14ce>] perf_trace_power+0xbe/0xe0
[ 61.111915] [<ffffffff8100ab2f>] ? mwait_idle+0x40f/0x4c0
[ 61.111918] [<ffffffff8100ab2f>] mwait_idle+0x40f/0x4c0
[ 61.111922] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.111926] [<ffffffff8174f49f>] rest_init+0x133/0x144
[ 61.111929] [<ffffffff8174f3e5>] ? rest_init+0x79/0x144
[ 61.111933] [<ffffffff81cc2b51>] start_kernel+0x35b/0x366
[ 61.111937] [<ffffffff81cc2321>] x86_64_start_reservations+0x131/0x135
[ 61.111940] [<ffffffff81cc2415>] x86_64_start_kernel+0xf0/0xf7
[ 61.111943] ---[ end trace 18a36211154afbbc ]---
[ 61.111946]
[ 61.111947] ===============================
[ 61.111949] [ INFO: suspicious RCU usage. ]
[ 61.111950] 3.3.0-rc1+ #572 Tainted: G W
[ 61.111952] -------------------------------
[ 61.111954] kernel/events/ring_buffer.c:120 suspicious rcu_dereference_check() usage!
[ 61.111956]
[ 61.111957] other info that might help us debug this:
[ 61.111958]
[ 61.111960]
[ 61.111960] rcu_scheduler_active = 1, debug_locks = 1
[ 61.111962] RCU used illegally from extended quiescent state!
[ 61.111964] 2 locks held by swapper/0/0:
[ 61.111966] #0: (rcu_read_lock){.+.+..}, at: [<ffffffff810f8d85>] __perf_event_overflow+0x145/0x2c0
[ 61.111974] #1: (rcu_read_lock){.+.+..}, at: [<ffffffff810fbfcf>] perf_output_begin+0x3f/0x330
[ 61.111980]
[ 61.111980] stack backtrace:
[ 61.111982] Pid: 0, comm: swapper/0 Tainted: G W 3.3.0-rc1+ #572
[ 61.111984] Call Trace:
[ 61.111987] [<ffffffff810949ba>] lockdep_rcu_suspicious+0xca/0xf0
[ 61.111990] [<ffffffff810fc1f8>] perf_output_begin+0x268/0x330
[ 61.111993] [<ffffffff810fbfcf>] ? perf_output_begin+0x3f/0x330
[ 61.111997] [<ffffffff81076975>] ? sched_clock_cpu+0xc5/0x120
[ 61.111999] [<ffffffff8109371d>] ? trace_hardirqs_off+0xd/0x10
[ 61.112003] [<ffffffff81076a1f>] ? local_clock+0x4f/0x60
[ 61.112006] [<ffffffff810f21cd>] ? __perf_event_header__init_id+0xad/0xf0
[ 61.112009] [<ffffffff810f8b93>] ? perf_prepare_sample+0x63/0x110
[ 61.112013] [<ffffffff810f8dcd>] __perf_event_overflow+0x18d/0x2c0
[ 61.112015] [<ffffffff810f8d85>] ? __perf_event_overflow+0x145/0x2c0
[ 61.112019] [<ffffffff817711ae>] ? printk+0x41/0x43
[ 61.112022] [<ffffffff810f8fa9>] perf_swevent_overflow+0xa9/0xc0
[ 61.112024] [<ffffffff810f902f>] perf_swevent_event+0x6f/0x90
[ 61.112028] [<ffffffff810f90c6>] perf_tp_event+0x76/0xf0
[ 61.112031] [<ffffffff810f14ce>] perf_trace_power+0xbe/0xe0
[ 61.112034] [<ffffffff8100ab2f>] ? mwait_idle+0x40f/0x4c0
[ 61.112038] [<ffffffff8100ab2f>] mwait_idle+0x40f/0x4c0
[ 61.112041] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.112044] [<ffffffff8174f49f>] rest_init+0x133/0x144
[ 61.112047] [<ffffffff8174f3e5>] ? rest_init+0x79/0x144
[ 61.112050] [<ffffffff81cc2b51>] start_kernel+0x35b/0x366
[ 61.112053] [<ffffffff81cc2321>] x86_64_start_reservations+0x131/0x135
[ 61.112057] [<ffffffff81cc2415>] x86_64_start_kernel+0xf0/0xf7
[ 61.112059] ------------[ cut here ]------------
[ 61.112062] WARNING: at include/linux/rcupdate.h:248 perf_output_end+0x5b/0x70()
[ 61.112064] Hardware name: ProLiant BL460c G6
[ 61.112065] Modules linked in: ipmi_devintf nfsd exportfs hpilo ipmi_si bnx2x crc32c libcrc32c mdio [last unloaded: scsi_wait_scan]
[ 61.112076] Pid: 0, comm: swapper/0 Tainted: G W 3.3.0-rc1+ #572
[ 61.112078] Call Trace:
[ 61.112081] [<ffffffff81038eaf>] warn_slowpath_common+0x7f/0xc0
[ 61.112085] [<ffffffff81038f0a>] warn_slowpath_null+0x1a/0x20
[ 61.112088] [<ffffffff810fc31b>] perf_output_end+0x5b/0x70
[ 61.112091] [<ffffffff810f8e6c>] __perf_event_overflow+0x22c/0x2c0
[ 61.112094] [<ffffffff810f8d85>] ? __perf_event_overflow+0x145/0x2c0
[ 61.112097] [<ffffffff810f8fa9>] perf_swevent_overflow+0xa9/0xc0
[ 61.112101] [<ffffffff810f902f>] perf_swevent_event+0x6f/0x90
[ 61.112104] [<ffffffff810f90c6>] perf_tp_event+0x76/0xf0
[ 61.112107] [<ffffffff810f14ce>] perf_trace_power+0xbe/0xe0
[ 61.112110] [<ffffffff8100ab2f>] ? mwait_idle+0x40f/0x4c0
[ 61.112113] [<ffffffff8100ab2f>] mwait_idle+0x40f/0x4c0
[ 61.112116] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.112120] [<ffffffff8174f49f>] rest_init+0x133/0x144
[ 61.112122] ------------[ cut here ]------------
[ 61.112126] WARNING: at include/linux/rcupdate.h:248 perf_output_end+0x5b/0x70()
[ 61.112128] Hardware name: ProLiant BL460c G6
[ 61.112129] Modules linked in: ipmi_devintf nfsd exportfs hpilo [<ffffffff8174f3e5>] ? rest_init+0x79/0x144
[ 61.112137] [<ffffffff81cc2b51>] start_kernel+0x35b/0x366
[ 61.112138] ipmi_si bnx2x [<ffffffff81cc2321>] x86_64_start_reservations+0x131/0x135
[ 61.112143] crc32c libcrc32c mdio [last unloaded: scsi_wait_scan]
[ 61.112148] Pid: 0, comm: swapper/2 Tainted: G W 3.3.0-rc1+ #572
[ 61.112150] [<ffffffff81cc2415>] x86_64_start_kernel+0xf0/0xf7
[ 61.112152] ---[ end trace 18a36211154afbbd ]---
[ 61.112153] ------------[ cut here ]------------
[ 61.112155] WARNING: at include/linux/rcupdate.h:248 __perf_event_overflow+0x2a6/0x2c0()
[ 61.112156] Hardware name: ProLiant BL460c G6
[ 61.112157] Modules linked in: ipmi_devintf nfsd exportfs hpilo ipmi_si bnx2x crc32c libcrc32c mdio [last unloaded: scsi_wait_scan]
[ 61.112165] Pid: 0, comm: swapper/0 Tainted: G W 3.3.0-rc1+ #572
[ 61.112166] Call Trace:
[ 61.112168] [<ffffffff81038eaf>] warn_slowpath_common+0x7f/0xc0
[ 61.112170] Call Trace:
[ 61.112172] [<ffffffff81038f0a>] warn_slowpath_null+0x1a/0x20
[ 61.112176] [<ffffffff81038eaf>] warn_slowpath_common+0x7f/0xc0
[ 61.112178] [<ffffffff810f8ee6>] __perf_event_overflow+0x2a6/0x2c0
[ 61.112182] [<ffffffff81038f0a>] warn_slowpath_null+0x1a/0x20
[ 61.112184] [<ffffffff810f8d85>] ? __perf_event_overflow+0x145/0x2c0
[ 61.112186] [<ffffffff810f8fa9>] perf_swevent_overflow+0xa9/0xc0
[ 61.112189] [<ffffffff810fc31b>] perf_output_end+0x5b/0x70
[ 61.112191] [<ffffffff810f902f>] perf_swevent_event+0x6f/0x90
[ 61.112193] [<ffffffff810f90c6>] perf_tp_event+0x76/0xf0
[ 61.112196] [<ffffffff810f8e6c>] __perf_event_overflow+0x22c/0x2c0
[ 61.112199] [<ffffffff810f14ce>] perf_trace_power+0xbe/0xe0
[ 61.112202] [<ffffffff8100ab2f>] ? mwait_idle+0x40f/0x4c0
[ 61.112205] [<ffffffff810f8d85>] ? __perf_event_overflow+0x145/0x2c0
[ 61.112207] [<ffffffff8100ab2f>] mwait_idle+0x40f/0x4c0
[ 61.112209] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.112212] [<ffffffff8174f49f>] rest_init+0x133/0x144
[ 61.112214] [<ffffffff810f8fa9>] perf_swevent_overflow+0xa9/0xc0
[ 61.112217] [<ffffffff810f902f>] perf_swevent_event+0x6f/0x90
[ 61.112219] [<ffffffff8174f3e5>] ? rest_init+0x79/0x144
[ 61.112222] [<ffffffff810f90c6>] perf_tp_event+0x76/0xf0
[ 61.112227] [<ffffffff8102009d>] ? lapic_next_event+0x1d/0x30
[ 61.112229] [<ffffffff81cc2b51>] start_kernel+0x35b/0x366
[ 61.112232] [<ffffffff81cc2321>] x86_64_start_reservations+0x131/0x135
[ 61.112235] [<ffffffff810f14ce>] perf_trace_power+0xbe/0xe0
[ 61.112238] [<ffffffff81cc2415>] x86_64_start_kernel+0xf0/0xf7
[ 61.112239] ---[ end trace 18a36211154afbbe ]---
[ 61.112242] [<ffffffff8100ab2f>] ? mwait_idle+0x40f/0x4c0
[ 61.112245] [<ffffffff8100ab2f>] mwait_idle+0x40f/0x4c0
[ 61.112248] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.112252] [<ffffffff8176baee>] start_secondary+0x1df/0x1e3
[ 61.112254] ---[ end trace 18a36211154afbbf ]---
[ 61.114605]
[ 61.114608] ===============================
[ 61.114611] [ INFO: suspicious RCU usage. ]
[ 61.114614] 3.3.0-rc1+ #572 Tainted: G W
[ 61.114616] -------------------------------
[ 61.114620] include/trace/events/power.h:127 suspicious rcu_dereference_check() usage!
[ 61.114625]
[ 61.114626] other info that might help us debug this:
[ 61.114628]
[ 61.114630]
[ 61.114630] rcu_scheduler_active = 1, debug_locks = 1
[ 61.114633] RCU used illegally from extended quiescent state!
[ 61.114635] no locks held by swapper/2/0.
[ 61.114637]
[ 61.114638] stack backtrace:
[ 61.114641] Pid: 0, comm: swapper/2 Tainted: G W 3.3.0-rc1+ #572
[ 61.114645] Call Trace:
[ 61.114650] [<ffffffff810949ba>] lockdep_rcu_suspicious+0xca/0xf0
[ 61.114655] [<ffffffff8100a9cd>] mwait_idle+0x2ad/0x4c0
[ 61.114660] [<ffffffff810011e8>] cpu_idle+0x98/0xe0
[ 61.114664] [<ffffffff8176baee>] start_secondary+0x1df/0x1e3
--
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