Commit-ID: d0981a1b21a03866c8da7f44e35e389c2e0d6061
Gitweb: http://git.kernel.org/tip/d0981a1b21a03866c8da7f44e35e389c2e0d6061
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 19 Aug 2009 11:26:09 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 19 Aug 2009 11:42:48 +0200
clocksource: Protect the watchdog rating changes with clocksource_mutex
Martin pointed out that commit 6ea41d2529 (clocksource: Call
clocksource_change_rating() outside of watchdog_lock) has a
theoretical reference count problem. The calls to
clocksource_change_rating() are now done outside of the clocksource
mutex and outside of the watchdog lock. A concurrent
clocksource_unregister() could remove the clock.
Split out the code which changes the rating from
clocksource_change_rating() into __clocksource_change_rating().
Protect the clocksource_watchdog_work() code sequence with the
clocksource_mutex() and call __clocksource_change_rating().
LKML-Reference: <alpine.LFD.2.00.0908171038420.2782@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
kernel/time/clocksource.c | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 02dc22d..c6bff11 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -131,6 +131,7 @@ static cycle_t watchdog_last;
static int watchdog_running;
static void clocksource_watchdog_work(struct work_struct *work);
+static void __clocksource_change_rating(struct clocksource *cs, int rating);
/*
* Interval: 0.5sec Threshold: 0.0625s
@@ -309,6 +310,7 @@ static void clocksource_watchdog_work(struct work_struct *work)
unsigned long flags;
LIST_HEAD(unstable);
+ mutex_lock(&clocksource_mutex);
spin_lock_irqsave(&watchdog_lock, flags);
list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
@@ -322,8 +324,9 @@ static void clocksource_watchdog_work(struct work_struct *work)
/* Needs to be done outside of watchdog lock */
list_for_each_entry_safe(cs, tmp, &unstable, wd_list) {
list_del_init(&cs->wd_list);
- clocksource_change_rating(cs, 0);
+ __clocksource_change_rating(cs, 0);
}
+ mutex_unlock(&clocksource_mutex);
}
#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
@@ -470,16 +473,21 @@ int clocksource_register(struct clocksource *cs)
}
EXPORT_SYMBOL(clocksource_register);
+static void __clocksource_change_rating(struct clocksource *cs, int rating)
+{
+ list_del(&cs->list);
+ cs->rating = rating;
+ clocksource_enqueue(cs);
+ clocksource_select();
+}
+
/**
* clocksource_change_rating - Change the rating of a registered clocksource
*/
void clocksource_change_rating(struct clocksource *cs, int rating)
{
mutex_lock(&clocksource_mutex);
- list_del(&cs->list);
- cs->rating = rating;
- clocksource_enqueue(cs);
- clocksource_select();
+ __clocksource_change_rating(cs, rating);
mutex_unlock(&clocksource_mutex);
}
EXPORT_SYMBOL(clocksource_change_rating);
--
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