Patchwork [v3,18/45] time/clocksource: Use get/put_online_cpus_atomic() to prevent CPU offline

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Submitter Srivatsa S. Bhat
Date June 27, 2013, 7:55 p.m.
Message ID <20130627195554.29830.38682.stgit@srivatsabhat.in.ibm.com>
Download mbox | patch
Permalink /patch/255139/
State Not Applicable
Delegated to: David Miller
Headers show

Comments

Srivatsa S. Bhat - June 27, 2013, 7:55 p.m.
Once stop_machine() is gone from the CPU offline path, we won't be able
to depend on disabling preemption to prevent CPUs from going offline
from under us.

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going
offline, while invoking from atomic context.

Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 kernel/time/clocksource.c |    5 +++++
 1 file changed, 5 insertions(+)


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Patch

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index e713ef7..c4bbc25 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -30,6 +30,7 @@ 
 #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
 #include <linux/tick.h>
 #include <linux/kthread.h>
+#include <linux/cpu.h>
 
 #include "tick-internal.h"
 
@@ -252,6 +253,7 @@  static void clocksource_watchdog(unsigned long data)
 	int64_t wd_nsec, cs_nsec;
 	int next_cpu, reset_pending;
 
+	get_online_cpus_atomic();
 	spin_lock(&watchdog_lock);
 	if (!watchdog_running)
 		goto out;
@@ -329,6 +331,7 @@  static void clocksource_watchdog(unsigned long data)
 	add_timer_on(&watchdog_timer, next_cpu);
 out:
 	spin_unlock(&watchdog_lock);
+	put_online_cpus_atomic();
 }
 
 static inline void clocksource_start_watchdog(void)
@@ -367,6 +370,7 @@  static void clocksource_enqueue_watchdog(struct clocksource *cs)
 {
 	unsigned long flags;
 
+	get_online_cpus_atomic();
 	spin_lock_irqsave(&watchdog_lock, flags);
 	if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
 		/* cs is a clocksource to be watched. */
@@ -386,6 +390,7 @@  static void clocksource_enqueue_watchdog(struct clocksource *cs)
 	/* Check if the watchdog timer needs to be started. */
 	clocksource_start_watchdog();
 	spin_unlock_irqrestore(&watchdog_lock, flags);
+	put_online_cpus_atomic();
 }
 
 static void clocksource_dequeue_watchdog(struct clocksource *cs)