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Subject[GIT pull] time(r) fixes for 5.6-rc1
Linus,

please pull the latest timers/urgent branch from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-2020-02-09

up to: febac332a819: clocksource: Prevent double add_timer_on() for watchdog_timer


Two small fixes for the time(r) subsystem:

- Handle a subtle race between the clocksource watchdog and a concurrent
clocksource watchdog stop/start sequence correctly to prevent a timer
double add bug.

- Fix the file path for the core time namespace file.


Thanks,

tglx

------------------>
Dmitry Safonov (1):
MAINTAINERS: Correct path to time namespace source file

Konstantin Khlebnikov (1):
clocksource: Prevent double add_timer_on() for watchdog_timer


MAINTAINERS | 2 +-
kernel/time/clocksource.c | 11 +++++++++--
2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 141b8d3e4ca2..3a4163be98da 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13267,7 +13267,7 @@ S: Maintained
F: fs/timerfd.c
F: include/linux/timer*
F: include/linux/time_namespace.h
-F: kernel/time_namespace.c
+F: kernel/time/namespace.c
F: kernel/time/*timer*

POWER MANAGEMENT CORE
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index fff5f64981c6..428beb69426a 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -293,8 +293,15 @@ static void clocksource_watchdog(struct timer_list *unused)
next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
if (next_cpu >= nr_cpu_ids)
next_cpu = cpumask_first(cpu_online_mask);
- watchdog_timer.expires += WATCHDOG_INTERVAL;
- add_timer_on(&watchdog_timer, next_cpu);
+
+ /*
+ * Arm timer if not already pending: could race with concurrent
+ * pair clocksource_stop_watchdog() clocksource_start_watchdog().
+ */
+ if (!timer_pending(&watchdog_timer)) {
+ watchdog_timer.expires += WATCHDOG_INTERVAL;
+ add_timer_on(&watchdog_timer, next_cpu);
+ }
out:
spin_unlock(&watchdog_lock);
}
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