FAILED: patch "[PATCH] hrtimer: Report offline hrtimer enqueue" failed to apply to 4.19-stable tree

PATCH In review [email protected] 2 participants 3 messages Feb 13, 2024

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Stable branch High-resolution timers, timer wheel, clockevents

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author maintainer

2024-02-13 13:00 UTC #0 lore raw

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x dad6a09f3148257ac1773cd90934d721d68ab595
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024021300-sagging-enhance-9113@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

dad6a09f3148 ("hrtimer: Report offline hrtimer enqueue") 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier") f61eff83cec9 ("hrtimer: Prepare support for PREEMPT_RT")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From dad6a09f3148257ac1773cd90934d721d68ab595 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <[email protected]>
Date: Mon, 29 Jan 2024 15:56:36 -0800
Subject: [PATCH] hrtimer: Report offline hrtimer enqueue

The hrtimers migration on CPU-down hotplug process has been moved earlier, before the CPU actually goes to die. This leaves a small window of opportunity to queue an hrtimer in a blind spot, leaving it ignored.

For example a practical case has been reported with RCU waking up a SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that way a sched/rt timer to the local offline CPU.

Make sure such situations never go unnoticed and warn when that happens.

Fixes 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")

Reported-by Paul E. McKenney <[email protected]>

Signed-off-by Frederic Weisbecker <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Cc [email protected]

Link https://lore.kernel.org/r/[email protected] open here

include/linux/hrtimer.h +3 -1

index 87e3bedf8eb0..641c4567cfa7 100644
@@ -157,6 +157,7 @@ enum  hrtimer_base_type {
  * @max_hang_time:	Maximum time spent in hrtimer_interrupt
  * @softirq_expiry_lock: Lock which is taken while softirq based hrtimer are
  *			 expired
+ * @online:		CPU is online from an hrtimers point of view
  * @timer_waiters:	A hrtimer_cancel() invocation waits for the timer
  *			callback to finish.
  * @expires_next:	absolute time of the next event, is required for remote

@@ -179,7 +180,8 @@ struct hrtimer_cpu_base {
 	unsigned int			hres_active		: 1,
 					in_hrtirq		: 1,
 					hang_detected		: 1,
-					softirq_activated       : 1;
+					softirq_activated       : 1,
+					online			: 1;
 #ifdef CONFIG_HIGH_RES_TIMERS
 	unsigned int			nr_events;
 	unsigned short			nr_retries;

kernel/time/hrtimer.c +3 -0

index 760793998cdd..edb0f821dcea 100644
@@ -1085,6 +1085,7 @@ static int enqueue_hrtimer(struct hrtimer *timer,
 			   enum hrtimer_mode mode)
 {
 	debug_activate(timer, mode);
+	WARN_ON_ONCE(!base->cpu_base->online);
 
 	base->cpu_base->active_bases |= 1 << base->index;

@@ -2183,6 +2184,7 @@ int hrtimers_prepare_cpu(unsigned int cpu)
 	cpu_base->softirq_next_timer = NULL;
 	cpu_base->expires_next = KTIME_MAX;
 	cpu_base->softirq_expires_next = KTIME_MAX;
+	cpu_base->online = 1;
 	hrtimer_cpu_base_init_expiry_lock(cpu_base);
 	return 0;
 }

@@ -2250,6 +2252,7 @@ int hrtimers_cpu_dying(unsigned int dying_cpu)
 	smp_call_function_single(ncpu, retrigger_next_event, NULL, 0);
 
 	raw_spin_unlock(&new_base->lock);
+	old_base->online = 0;
 	raw_spin_unlock(&old_base->lock);
 
 	return 0;

Thomas Gleixner

2024-02-13 15:29 UTC #1 lore raw

PATCH 1/1 hrtimer: Report offline hrtimer enqueue

From: Frederic Weisbecker <[email protected]>

commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream.

For example a practical case has been reported with RCU waking up a SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that way a sched/rt timer to the local offline CPU.

Make sure such situations never go unnoticed and warn when that happens.

Fixes 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")

Reported-by Paul E. McKenney <[email protected]>

Signed-off-by Frederic Weisbecker <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Cc [email protected]

Link https://lore.kernel.org/r/[email protected] open here

---

Backport to 4.19 as tglx has too much spare time...

---
 include/linux/hrtimer.h |    4 +++-
 kernel/time/hrtimer.c   |    3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

include/linux/hrtimer.h +3 -1

@@ -182,6 +182,7 @@ enum  hrtimer_base_type {
  * @hang_detected:	The last hrtimer interrupt detected a hang
  * @softirq_activated:	displays, if the softirq is raised - update of softirq
  *			related settings is not required then.
+ * @online:		CPU is online from an hrtimers point of view
  * @nr_events:		Total number of hrtimer interrupt events
  * @nr_retries:		Total number of hrtimer interrupt retries
  * @nr_hangs:		Total number of hrtimer interrupt hangs

@@ -206,7 +207,8 @@ struct hrtimer_cpu_base {
 	unsigned int			hres_active		: 1,
 					in_hrtirq		: 1,
 					hang_detected		: 1,
-					softirq_activated       : 1;
+					softirq_activated       : 1,
+					online			: 1;
 #ifdef CONFIG_HIGH_RES_TIMERS
 	unsigned int			nr_events;
 	unsigned short			nr_retries;

kernel/time/hrtimer.c +3 -0

@@ -970,6 +970,7 @@ static int enqueue_hrtimer(struct hrtime
 			   enum hrtimer_mode mode)
 {
 	debug_activate(timer, mode);
+	WARN_ON_ONCE(!base->cpu_base->online);
 
 	base->cpu_base->active_bases |= 1 << base->index;

@@ -1887,6 +1888,7 @@ int hrtimers_prepare_cpu(unsigned int cp
 	cpu_base->softirq_next_timer = NULL;
 	cpu_base->expires_next = KTIME_MAX;
 	cpu_base->softirq_expires_next = KTIME_MAX;
+	cpu_base->online = 1;
 	return 0;
 }

@@ -1953,6 +1955,7 @@ int hrtimers_cpu_dying(unsigned int dyin
 	smp_call_function_single(ncpu, retrigger_next_event, NULL, 0);
 
 	raw_spin_unlock(&new_base->lock);
+	old_base->online = 0;
 	raw_spin_unlock(&old_base->lock);
 
 	return 0;

Greg KH

author maintainer

2024-02-13 16:19 UTC #2 lore raw

Re: [PATCH 4.19] hrtimer: Report offline hrtimer enqueue

Quoted 22 lines · Thomas Gleixner

From: Frederic Weisbecker <[email protected]>
commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream.
The hrtimers migration on CPU-down hotplug process has been moved earlier, before the CPU actually goes to die. This leaves a small window of opportunity to queue an hrtimer in a blind spot, leaving it ignored.
For example a practical case has been reported with RCU waking up a SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that way a sched/rt timer to the local offline CPU.
Make sure such situations never go unnoticed and warn when that happens.
Fixes 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Reported-by Paul E. McKenney <[email protected]>
Signed-off-by Frederic Weisbecker <[email protected]>
Signed-off-by Paul E. McKenney <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc [email protected]
Link https://lore.kernel.org/r/[email protected] open here

Quoted 3 lines

---
Backport to 4.19 as tglx has too much spare time...

Now queued up, thanks.

greg k-h