linux-kernel - [tip:perf/urgent] watchdog: Fix broken nowatchdog logic

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Message-ID: <tip-4135038a582c20ffdadfcf6564852e0b72a20968@git.kernel.org>
Date:	Mon, 31 Jan 2011 12:51:30 GMT
From:	tip-bot for Marcin Slusarz <marcin.slusarz@...il.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com, hpa@...or.com,
	mingo@...hat.com, a.p.zijlstra@...llo.nl, marcin.slusarz@...il.com,
	fweisbec@...il.com, stable@...nel.org, tglx@...utronix.de,
	mingo@...e.hu, dzickus@...hat.com
Subject: [tip:perf/urgent] watchdog: Fix broken nowatchdog logic

Commit-ID:  4135038a582c20ffdadfcf6564852e0b72a20968
Gitweb:     http://git.kernel.org/tip/4135038a582c20ffdadfcf6564852e0b72a20968
Author:     Marcin Slusarz <marcin.slusarz@...il.com>
AuthorDate: Fri, 28 Jan 2011 11:00:31 -0500
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Mon, 31 Jan 2011 13:22:42 +0100

watchdog: Fix broken nowatchdog logic

Passing nowatchdog to kernel disables 2 things: creation of
watchdog threads AND initialization of percpu watchdog_hrtimer.
As hrtimers are initialized only at boot it's not possible to
enable watchdog later - for me all watchdog threads started to
eat 100% of CPU time, but they could just crash.

Additionally, even if these threads would start properly,
watchdog_disable_all_cpus was guarded by no_watchdog check, so
you couldn't disable watchdog.

To fix this, remove no_watchdog variable and use already
existing watchdog_enabled variable.

Signed-off-by: Marcin Slusarz <marcin.slusarz@...il.com>
[ removed another no_watchdog instance ]
Signed-off-by: Don Zickus <dzickus@...hat.com>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: <stable@...nel.org>
LKML-Reference: <1296230433-6261-1-git-send-email-dzickus@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/watchdog.c |   20 ++++++--------------
 1 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index d7ebdf4..d9961ea 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -27,7 +27,7 @@
 #include <asm/irq_regs.h>
 #include <linux/perf_event.h>
 
-int watchdog_enabled;
+int watchdog_enabled = 1;
 int __read_mostly softlockup_thresh = 60;
 
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
@@ -43,9 +43,6 @@ static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
 #endif
 
-static int no_watchdog;
-
-
 /* boot commands */
 /*
  * Should we panic when a soft-lockup or hard-lockup occurs:
@@ -58,7 +55,7 @@ static int __init hardlockup_panic_setup(char *str)
 	if (!strncmp(str, "panic", 5))
 		hardlockup_panic = 1;
 	else if (!strncmp(str, "0", 1))
-		no_watchdog = 1;
+		watchdog_enabled = 0;
 	return 1;
 }
 __setup("nmi_watchdog=", hardlockup_panic_setup);
@@ -77,7 +74,7 @@ __setup("softlockup_panic=", softlockup_panic_setup);
 
 static int __init nowatchdog_setup(char *str)
 {
-	no_watchdog = 1;
+	watchdog_enabled = 0;
 	return 1;
 }
 __setup("nowatchdog", nowatchdog_setup);
@@ -85,7 +82,7 @@ __setup("nowatchdog", nowatchdog_setup);
 /* deprecated */
 static int __init nosoftlockup_setup(char *str)
 {
-	no_watchdog = 1;
+	watchdog_enabled = 0;
 	return 1;
 }
 __setup("nosoftlockup", nosoftlockup_setup);
@@ -476,9 +473,6 @@ static void watchdog_disable_all_cpus(void)
 {
 	int cpu;
 
-	if (no_watchdog)
-		return;
-
 	for_each_online_cpu(cpu)
 		watchdog_disable(cpu);
 
@@ -530,7 +524,8 @@ cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 		break;
 	case CPU_ONLINE:
 	case CPU_ONLINE_FROZEN:
-		err = watchdog_enable(hotcpu);
+		if (watchdog_enabled)
+			err = watchdog_enable(hotcpu);
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
 	case CPU_UP_CANCELED:
@@ -555,9 +550,6 @@ void __init lockup_detector_init(void)
 	void *cpu = (void *)(long)smp_processor_id();
 	int err;
 
-	if (no_watchdog)
-		return;
-
 	err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 	WARN_ON(notifier_to_errno(err));
 
--
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