From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752041AbdEJE75 (ORCPT ); Wed, 10 May 2017 00:59:57 -0400 Received: from ozlabs.org ([103.22.144.67]:34143 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751760AbdEJE74 (ORCPT ); Wed, 10 May 2017 00:59:56 -0400 From: Michael Ellerman To: Thomas Gleixner , LKML Cc: Peter Zijlstra , Ingo Molnar , Steven Rostedt , Sebastian Siewior Subject: Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu rwsem In-Reply-To: <20170418170554.382344438@linutronix.de> References: <20170418170442.665445272@linutronix.de> <20170418170554.382344438@linutronix.de> User-Agent: Notmuch/0.21 (https://notmuchmail.org) Date: Wed, 10 May 2017 14:59:51 +1000 Message-ID: <87o9v171dk.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thomas Gleixner writes: > @@ -130,6 +130,7 @@ void __static_key_slow_inc(struct static > * the all CPUs, for that to be serialized against CPU hot-plug > * we need to avoid CPUs coming online. > */ > + lockdep_assert_hotplug_held(); > jump_label_lock(); > if (atomic_read(&key->enabled) == 0) { > atomic_set(&key->enabled, -1); I seem to be hitting this assert from the ftrace event selftests, enabled at boot with CONFIG_FTRACE_STARTUP_TEST=y, using next-20170509 (on powerpc). [ 842.691191] Testing event rpc_call_status: [ 842.691209] ------------[ cut here ]------------ [ 842.691399] WARNING: CPU: 6 PID: 1 at ../kernel/cpu.c:234 lockdep_assert_hotplug_held+0x5c/0x70 [ 842.691575] Modules linked in: [ 842.691675] CPU: 6 PID: 1 Comm: swapper/0 Tainted: G W 4.11.0-gcc-5.4.1-next-20170509 #218 [ 842.691865] task: c0000001fe780000 task.stack: c0000001fe800000 [ 842.692003] NIP: c0000000000ff3dc LR: c0000000000ff3d0 CTR: c000000000218650 [ 842.692166] REGS: c0000001fe8036e0 TRAP: 0700 Tainted: G W (4.11.0-gcc-5.4.1-next-20170509) [ 842.692343] MSR: 8000000000029033 [ 842.692491] CR: 28002222 XER: 20000000 [ 842.692689] CFAR: c000000000171530 SOFTE: 1 GPR00: c0000000000ff3d0 c0000001fe803960 c0000000012b7600 0000000000000000 GPR04: ffffffffffffffff 0000000000000000 c0000000fc10c0e8 0000000000000000 GPR08: 0000000000000000 0000000000000000 0000000000000000 c0000000f8180008 GPR12: 0000000000002200 c00000000fd42100 c00000000000e218 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 0000000000000000 0000000000000000 c0000000f9341610 GPR24: c00000000127ee48 c000000000aa49d0 000000000000000a c0000000fc3c0000 GPR28: c00000000117b148 c000000001264230 0000000000000000 c00000000127ee48 [ 842.694287] NIP [c0000000000ff3dc] lockdep_assert_hotplug_held+0x5c/0x70 [ 842.694434] LR [c0000000000ff3d0] lockdep_assert_hotplug_held+0x50/0x70 [ 842.694577] Call Trace: [ 842.694658] [c0000001fe803960] [c0000000000ff3d0] lockdep_assert_hotplug_held+0x50/0x70 (unreliable) [ 842.694876] [c0000001fe803980] [c0000000002a3754] __static_key_slow_inc+0x104/0x170 [ 842.695054] [c0000001fe8039f0] [c0000000002176ac] tracepoint_probe_register_prio+0x2dc/0x390 [ 842.695258] [c0000001fe803a60] [c00000000024cf50] trace_event_reg+0xe0/0x130 [ 842.695434] [c0000001fe803a80] [c00000000024d5f0] __ftrace_event_enable_disable+0x270/0x3e0 [ 842.695601] [c0000001fe803b10] [c000000000e20328] event_trace_self_tests+0x14c/0x350 [ 842.695778] [c0000001fe803bc0] [c000000000e20774] event_trace_self_tests_init+0xc8/0xf4 [ 842.695944] [c0000001fe803c30] [c00000000000d87c] do_one_initcall+0x6c/0x1d0 [ 842.696113] [c0000001fe803cf0] [c000000000df462c] kernel_init_freeable+0x304/0x3e4 [ 842.696282] [c0000001fe803dc0] [c00000000000e23c] kernel_init+0x2c/0x170 [ 842.696460] [c0000001fe803e30] [c00000000000bdec] ret_from_kernel_thread+0x5c/0x70 [ 842.696662] Instruction dump: [ 842.696763] 409e0014 38210020 e8010010 7c0803a6 4e800020 3c62ffe6 3880ffff 38634808 [ 842.697009] 480720ed 60000000 2fa30000 409effd8 <0fe00000> 38210020 e8010010 7c0803a6 [ 842.697271] ---[ end trace f68728a0d30544a1 ]--- The stupidly obvious (or perhaps obviously stupid) patch below fixes it: diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index daefdee9411a..5531f7ce8fa6 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -3241,9 +3241,19 @@ static __init void event_trace_self_tests(void) continue; } + get_online_cpus(); + mutex_lock(&event_mutex); ftrace_event_enable_disable(file, 1); + mutex_unlock(&event_mutex); + put_online_cpus(); + event_test_stuff(); + + get_online_cpus(); + mutex_lock(&event_mutex); ftrace_event_enable_disable(file, 0); + mutex_unlock(&event_mutex); + put_online_cpus(); pr_cont("OK\n"); } cheers