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FAILED: patch "[PATCH] tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz" failed to apply to 4.14-stable tree

PATCH [email protected] 1 participant 1 message May 6, 2023

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Stable branch Driver core RCU Nohz, dynticks support
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The patch below does not apply to the 4.14-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-4.14.y
git checkout FETCH_HEAD
git cherry-pick -x 58d7668242647e661a20efe065519abd6454287e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023050606-jawed-amnesty-4b1c@gregkh' --subject-prefix 'PATCH 4.14.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 58d7668242647e661a20efe065519abd6454287e Mon Sep 17 00:00:00 2001
From: "Joel Fernandes (Google)" <[email protected]>
Date: Tue, 24 Jan 2023 17:31:26 +0000
Subject: [PATCH] tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz
subsystem

For CONFIG_NO_HZ_FULL systems, the tick_do_timer_cpu cannot be offlined. However, cpu_is_hotpluggable() still returns true for those CPUs. This causes torture tests that do offlining to end up trying to offline this CPU causing test failures. Such failure happens on all architectures.

Fix the repeated error messages thrown by this (even if the hotplug errors are harmless) by asking the opinion of the nohz subsystem on whether the CPU can be hotplugged.

[ Apply Frederic Weisbecker feedback on refactoring tick_nohz_cpu_down(). ]

For drivers/base/ portion:

Acked-by Greg Kroah-Hartman <[email protected]>
Acked-by Frederic Weisbecker <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc "Paul E. McKenney" <[email protected]>
Cc Zhouyi Zhou <[email protected]>
Cc Will Deacon <[email protected]>
Cc Marc Zyngier <[email protected]>
Cc rcu <[email protected]>
Cc [email protected]
Fixes 2987557f52b9 ("driver-core/cpu: Expose hotpluggability to the rest of the kernel")
Signed-off-by Paul E. McKenney <[email protected]>
Signed-off-by Joel Fernandes (Google) <[email protected]>
drivers/base/cpu.c +2 -1
index 182c6122f815..c1815b9dae68 100644
@@ -487,7 +487,8 @@ static const struct attribute_group *cpu_root_attr_groups[] = {
 bool cpu_is_hotpluggable(unsigned int cpu)
 {
 	struct device *dev = get_cpu_device(cpu);
-	return dev && container_of(dev, struct cpu, dev)->hotpluggable;
+	return dev && container_of(dev, struct cpu, dev)->hotpluggable
+		&& tick_nohz_cpu_hotpluggable(cpu);
 }
 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
include/linux/tick.h +2 -0
index bfd571f18cfd..9459fef5b857 100644
@@ -216,6 +216,7 @@ extern void tick_nohz_dep_set_signal(struct task_struct *tsk,
 				     enum tick_dep_bits bit);
 extern void tick_nohz_dep_clear_signal(struct signal_struct *signal,
 				       enum tick_dep_bits bit);
+extern bool tick_nohz_cpu_hotpluggable(unsigned int cpu);
 
 /*
  * The below are tick_nohz_[set,clear]_dep() wrappers that optimize off-cases

@@ -280,6 +281,7 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
 
 static inline void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }
 static inline void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { }
+static inline bool tick_nohz_cpu_hotpluggable(unsigned int cpu) { return true; }
 
 static inline void tick_dep_set(enum tick_dep_bits bit) { }
 static inline void tick_dep_clear(enum tick_dep_bits bit) { }
kernel/time/tick-sched.c +8 -3
index b0e3c9205946..68d81a4283c8 100644
@@ -527,7 +527,7 @@ void __init tick_nohz_full_setup(cpumask_var_t cpumask)
 	tick_nohz_full_running = true;
 }
 
-static int tick_nohz_cpu_down(unsigned int cpu)
+bool tick_nohz_cpu_hotpluggable(unsigned int cpu)
 {
 	/*
 	 * The tick_do_timer_cpu CPU handles housekeeping duty (unbound

@@ -535,8 +535,13 @@ static int tick_nohz_cpu_down(unsigned int cpu)
 	 * CPUs. It must remain online when nohz full is enabled.
 	 */
 	if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
-		return -EBUSY;
-	return 0;
+		return false;
+	return true;
+}
+
+static int tick_nohz_cpu_down(unsigned int cpu)
+{
+	return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
 }
 
 void __init tick_nohz_init(void)