From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752178AbcFNP2q (ORCPT ); Tue, 14 Jun 2016 11:28:46 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:34113 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751239AbcFNP2K (ORCPT ); Tue, 14 Jun 2016 11:28:10 -0400 From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Frederic Weisbecker , Ingo Molnar , Mike Galbraith , Thomas Gleixner Subject: [PATCH 1/3] sched: Introduce sched_time_avg_ns minimal value Date: Tue, 14 Jun 2016 17:28:00 +0200 Message-Id: <1465918082-27005-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1465918082-27005-1-git-send-email-fweisbec@gmail.com> References: <1465918082-27005-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Writing 0 to sysctl value "kernel.sched_time_avg_ms" triggers a lockup: NMI watchdog: Watchdog detected hard LOCKUP on cpu 4 Modules linked in: irq event stamp: 81894 hardirqs last enabled at (81893): [] rcu_idle_exit+0x68/0xa0 hardirqs last disabled at (81894): [] tick_nohz_idle_exit+0x2e/0x110 softirqs last enabled at (81870): [] _local_bh_enable+0x21/0x50 softirqs last disabled at (81869): [] irq_enter+0x4b/0x70 CPU: 4 PID: 0 Comm: swapper/4 Not tainted 4.6.0-rc4+ #269 Hardware name: MSI MS-7850/Z87-G41 PC Mate(MS-7850), BIOS V1.3 08/18/2013 0000000000000000 ffff88021fb05b80 ffffffff8141b023 0000000000000000 0000000000000004 ffff88021fb05ba0 ffffffff81163fcf 0000000000000000 ffff88021fb05c40 ffff88021fb05be0 ffffffff8119ae7c 00000001810077ce Call Trace: [] dump_stack+0x85/0xc2 [] watchdog_overflow_callback+0x13f/0x160 [] __perf_event_overflow+0x9c/0x1f0 [] perf_event_overflow+0x14/0x20 [] intel_pmu_handle_irq+0x1d5/0x4a0 [] perf_event_nmi_handler+0x2d/0x50 [] ? tracing_generic_entry_update+0x97/0xb0 [] nmi_handle+0xbf/0x2f0 [] ? nmi_handle+0x5/0x2f0 [] ? tracing_generic_entry_update+0x97/0xb0 [] default_do_nmi+0x71/0x1b0 [] do_nmi+0x115/0x170 [] end_repeat_nmi+0x1a/0x1e [] ? tracing_generic_entry_update+0x97/0xb0 [] ? tracing_generic_entry_update+0x97/0xb0 [] ? tracing_generic_entry_update+0x97/0xb0 <> [] ? trace_buffer_lock_reserve+0x3f/0x60 [] ? sched_avg_update+0x51/0xc0 [] __trace_bputs+0x75/0x100 [] sched_avg_update+0x79/0xc0 [] cpu_load_update+0xa3/0xd0 [] cpu_load_update_nohz_stop+0x7a/0x80 [] tick_nohz_idle_exit+0x77/0x110 [] cpu_startup_entry+0x176/0x420 [] start_secondary+0x104/0x110 This is due to the loop in sched_avg_update() that fails to make any progress when the update delay is 0. Since this is non-sense to set that value to 0 anyway, force a minimum of at least 1 millisecond. Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Frederic Weisbecker --- kernel/sysctl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 87b2fc3..b730dd6 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -345,7 +345,8 @@ static struct ctl_table kern_table[] = { .data = &sysctl_sched_time_avg, .maxlen = sizeof(unsigned int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = proc_dointvec_minmax, + .extra1 = &one, }, { .procname = "sched_shares_window_ns", -- 2.7.0