* [PATCH Resend] hrtimer: call switch_hrtimer_base() after setting new expiry time
@ 2014-05-12 8:12 Viresh Kumar
2014-05-12 8:51 ` [tip:timers/urgent] hrtimer: Set expiry time before switch_hrtimer_base() tip-bot for Viresh Kumar
0 siblings, 1 reply; 2+ messages in thread
From: Viresh Kumar @ 2014-05-12 8:12 UTC (permalink / raw)
To: tglx
Cc: linaro-kernel, linaro-networking, linux-kernel, fweisbec,
arvind.chauhan, Viresh Kumar
In switch_hrtimer_base() we are calling hrtimer_check_target() which guarantees
this:
/*
* With HIGHRES=y we do not migrate the timer when it is expiring
* before the next event on the target cpu because we cannot reprogram
* the target cpu hardware and we would cause it to fire late.
*
* Called with cpu_base->lock of target cpu held.
*/
But switch_hrtimer_base() is only called from one place, i.e.
__hrtimer_start_range_ns() and at that point (where we call
switch_hrtimer_base()) expiration time is not yet known as we call this routine
later: hrtimer_set_expires_range_ns().
To fix this, we need to find the updated expiry time before calling
switch_hrtimer_base().
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
Rebased over: v3.15-rc5
kernel/hrtimer.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6b715c0..e0501fe 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -990,11 +990,8 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
/* Remove an active timer from the queue: */
ret = remove_hrtimer(timer, base);
- /* Switch the timer base, if necessary: */
- new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
-
if (mode & HRTIMER_MODE_REL) {
- tim = ktime_add_safe(tim, new_base->get_time());
+ tim = ktime_add_safe(tim, base->get_time());
/*
* CONFIG_TIME_LOW_RES is a temporary way for architectures
* to signal that they simply return xtime in
@@ -1009,6 +1006,9 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
hrtimer_set_expires_range_ns(timer, tim, delta_ns);
+ /* Switch the timer base, if necessary: */
+ new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
+
timer_stats_hrtimer_set_start_info(timer);
leftmost = enqueue_hrtimer(timer, new_base);
--
2.0.0.rc2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [tip:timers/urgent] hrtimer: Set expiry time before switch_hrtimer_base()
2014-05-12 8:12 [PATCH Resend] hrtimer: call switch_hrtimer_base() after setting new expiry time Viresh Kumar
@ 2014-05-12 8:51 ` tip-bot for Viresh Kumar
0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Viresh Kumar @ 2014-05-12 8:51 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, viresh.kumar, tglx
Commit-ID: 84ea7fe37908254c3bd90910921f6e1045c1747a
Gitweb: http://git.kernel.org/tip/84ea7fe37908254c3bd90910921f6e1045c1747a
Author: Viresh Kumar <viresh.kumar@linaro.org>
AuthorDate: Mon, 12 May 2014 13:42:29 +0530
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 12 May 2014 10:47:39 +0200
hrtimer: Set expiry time before switch_hrtimer_base()
switch_hrtimer_base() calls hrtimer_check_target() which ensures that
we do not migrate a timer to a remote cpu if the timer expires before
the current programmed expiry time on that remote cpu.
But __hrtimer_start_range_ns() calls switch_hrtimer_base() before the
new expiry time is set. So the sanity check in hrtimer_check_target()
is operating on stale or even uninitialized data.
Update expiry time before calling switch_hrtimer_base().
[ tglx: Rewrote changelog once again ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: linaro-networking@linaro.org
Cc: fweisbec@gmail.com
Cc: arvind.chauhan@arm.com
Link: http://lkml.kernel.org/r/81999e148745fc51bbcd0615823fbab9b2e87e23.1399882253.git.viresh.kumar@linaro.org
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/hrtimer.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6b715c0..e0501fe 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -990,11 +990,8 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
/* Remove an active timer from the queue: */
ret = remove_hrtimer(timer, base);
- /* Switch the timer base, if necessary: */
- new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
-
if (mode & HRTIMER_MODE_REL) {
- tim = ktime_add_safe(tim, new_base->get_time());
+ tim = ktime_add_safe(tim, base->get_time());
/*
* CONFIG_TIME_LOW_RES is a temporary way for architectures
* to signal that they simply return xtime in
@@ -1009,6 +1006,9 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
hrtimer_set_expires_range_ns(timer, tim, delta_ns);
+ /* Switch the timer base, if necessary: */
+ new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
+
timer_stats_hrtimer_set_start_info(timer);
leftmost = enqueue_hrtimer(timer, new_base);
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2014-05-12 8:12 [PATCH Resend] hrtimer: call switch_hrtimer_base() after setting new expiry time Viresh Kumar
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