From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752111AbaATRfG (ORCPT ); Mon, 20 Jan 2014 12:35:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:5624 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbaATRfC (ORCPT ); Mon, 20 Jan 2014 12:35:02 -0500 From: atomlin@redhat.com To: linux-kernel@vger.kernel.org Cc: rientjes@google.com, mingo@kernel.org, oleg@redhat.com, riel@redhat.com, akpm@linux-foundation.org, atomlin@redhat.com Subject: [RFC PATCH v4 2/2] hung_task: Display every hung task warning Date: Mon, 20 Jan 2014 17:34:13 +0000 Message-Id: <1390239253-24030-3-git-send-email-atomlin@redhat.com> In-Reply-To: <1390239253-24030-1-git-send-email-atomlin@redhat.com> References: <1390239253-24030-1-git-send-email-atomlin@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Aaron Tomlin When khungtaskd detects hung tasks, it prints out backtraces from a number of those tasks. Limiting the number of backtraces being printed out can result in the user not seeing the information necessary to debug the issue. The hung_task_warnings sysctl controls this feature. This patch makes it possible for hung_task_warnings to accept a special value to print an unlimited number of backtraces when khungtaskd detects hung tasks. The special value is -1. To use this value it is necessary to change types from ulong to int. Signed-off-by: Aaron Tomlin Reviewed-by: Rik van Riel --- Documentation/sysctl/kernel.txt | 42 +++++++++++++++++++++++++++++++++++++++++ include/linux/sched/sysctl.h | 2 +- kernel/hung_task.c | 6 ++++-- kernel/sysctl.c | 5 +++-- 4 files changed, 50 insertions(+), 5 deletions(-) diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 26b7ee4..ff1a167 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -33,6 +33,10 @@ show up in /proc/sys/kernel: - domainname - hostname - hotplug +- hung_task_panic +- hung_task_check_count +- hung_task_timeout_secs +- hung_task_warnings - kptr_restrict - kstack_depth_to_print [ X86 only ] - l2cr [ PPC only ] @@ -287,6 +291,44 @@ Default value is "/sbin/hotplug". ============================================================== +hung_task_panic: + +Controls the kernel's behavior when a hung task is detected. +This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. + +0: continue operation. This is the default behavior. + +1: panic immediately. + +============================================================== + +hung_task_check_count: + +The upper bound on the number of tasks that are checked. +This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. + +============================================================== + +hung_task_timeout_secs: + +Check interval. When a task in D state did not get scheduled +for more than this value report a warning. +This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. + +0: means infinite timeout - no checking done. + +============================================================== + +hung_task_warning: + +The maximum number of warnings to report. During a check interval +When this value is reached, no more the warnings will be reported. +This file shows up if CONFIG_DETECT_HUNG_TASK is enabled. + +-1: report an infinite number of warnings. + +============================================================== + kptr_restrict: This toggle indicates whether restrictions are placed on diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 41467f8..eb3c72d7 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -5,7 +5,7 @@ extern int sysctl_hung_task_check_count; extern unsigned int sysctl_hung_task_panic; extern unsigned long sysctl_hung_task_timeout_secs; -extern unsigned long sysctl_hung_task_warnings; +extern int sysctl_hung_task_warnings; extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 9328b80..0b9c169 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -37,7 +37,7 @@ int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; */ unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT; -unsigned long __read_mostly sysctl_hung_task_warnings = 10; +int __read_mostly sysctl_hung_task_warnings = 10; static int __read_mostly did_panic; @@ -98,7 +98,9 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) if (!sysctl_hung_task_warnings) return; - sysctl_hung_task_warnings--; + + if (sysctl_hung_task_warnings > 0) + sysctl_hung_task_warnings--; /* * Ok, the task did not get scheduled for more than 2 minutes, diff --git a/kernel/sysctl.c b/kernel/sysctl.c index dd531a6..b50cd13 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -985,9 +985,10 @@ static struct ctl_table kern_table[] = { { .procname = "hung_task_warnings", .data = &sysctl_hung_task_warnings, - .maxlen = sizeof(unsigned long), + .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_doulongvec_minmax, + .proc_handler = proc_dointvec_minmax, + .extra1 = &neg_one, }, #endif #ifdef CONFIG_COMPAT -- 1.8.4.2