Commit-ID: 01548f4d3e8e94caf323a4f664eb347fd34a34ab
Gitweb: http://git.kernel.org/tip/01548f4d3e8e94caf323a4f664eb347fd34a34ab
Author: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
AuthorDate: Tue, 18 Aug 2009 17:09:42 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 19 Aug 2009 12:00:56 +0200
clocksource: Avoid clocksource watchdog circular locking dependency
stop_machine from a multithreaded workqueue is not allowed because
of a circular locking dependency between cpu_down and the workqueue
execution. Use a kernel thread to do the clocksource downgrade.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: john stultz <johnstul@xxxxxxxxxx>
LKML-Reference: <20090818170942.3ab80c91@skybase>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
kernel/time/clocksource.c | 19 ++++++++++++++++---
1 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c6bff11..e0c86ad 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -29,6 +29,7 @@
#include <linux/module.h>
#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
#include <linux/tick.h>
+#include <linux/kthread.h>
void timecounter_init(struct timecounter *tc,
const struct cyclecounter *cc,
@@ -130,7 +131,7 @@ static DEFINE_SPINLOCK(watchdog_lock);
static cycle_t watchdog_last;
static int watchdog_running;
-static void clocksource_watchdog_work(struct work_struct *work);
+static int clocksource_watchdog_kthread(void *data);
static void __clocksource_change_rating(struct clocksource *cs, int rating);
/*
@@ -139,6 +140,15 @@ static void __clocksource_change_rating(struct clocksource *cs, int rating);
#define WATCHDOG_INTERVAL (HZ >> 1)
#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
+static void clocksource_watchdog_work(struct work_struct *work)
+{
+ /*
+ * If kthread_run fails the next watchdog scan over the
+ * watchdog_list will find the unstable clock again.
+ */
+ kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
+}
+
static void clocksource_unstable(struct clocksource *cs, int64_t delta)
{
printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
@@ -167,8 +177,10 @@ static void clocksource_watchdog(unsigned long data)
list_for_each_entry(cs, &watchdog_list, wd_list) {
/* Clocksource already marked unstable? */
- if (cs->flags & CLOCK_SOURCE_UNSTABLE)
+ if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
+ schedule_work(&watchdog_work);
continue;
+ }
csnow = cs->read(cs);
@@ -304,7 +316,7 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs)
spin_unlock_irqrestore(&watchdog_lock, flags);
}
-static void clocksource_watchdog_work(struct work_struct *work)
+static int clocksource_watchdog_kthread(void *data)
{
struct clocksource *cs, *tmp;
unsigned long flags;
@@ -327,6 +339,7 @@ static void clocksource_watchdog_work(struct work_struct *work)
__clocksource_change_rating(cs, 0);
}
mutex_unlock(&clocksource_mutex);
+ return 0;
}
#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
--
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