linux-kernel - [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup

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Date:	Tue, 17 Aug 2010 10:56:12 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Don Zickus <dzickus@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and
 touch_softlockup_watchdog (v2)

Fix: acpi_os_stall calls touch_nmi_watchdog and touch_softlockup_watchdog
with preemption enabled causing 'BUG: using smp_processor_id() in preemptible 
code'.

Patch also removes double smp_processor_id call (smp_processor_id itself and
in __get_cpu_var) in __touch_watchdog.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

---

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 613bc1f..cb4f4d4 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -116,13 +116,14 @@ static unsigned long get_sample_period(void)
 static void __touch_watchdog(void)
 {
 	int this_cpu = smp_processor_id();
-
-	__get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
+	per_cpu(watchdog_touch_ts, this_cpu) = get_timestamp(this_cpu);
 }
 
 void touch_softlockup_watchdog(void)
 {
+	preempt_disable();
 	__get_cpu_var(watchdog_touch_ts) = 0;
+	preempt_enable();
 }
 EXPORT_SYMBOL(touch_softlockup_watchdog);
 
@@ -142,7 +143,10 @@ void touch_all_softlockup_watchdogs(void)
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 void touch_nmi_watchdog(void)
 {
+	preempt_disable();
 	__get_cpu_var(watchdog_nmi_touch) = true;
+	preempt_enable();
+
 	touch_softlockup_watchdog();
 }
 EXPORT_SYMBOL(touch_nmi_watchdog);

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