Patch "cpu/hotplug: Serialize callback invocations proper" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message May 5, 2017

Subsystems (2)

Stable branch CPU hotplug

lore

Share & tools

lore

[email protected]

author maintainer Applied

2017-05-05 18:42 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

cpu/hotplug: Serialize callback invocations proper

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cpu-hotplug-serialize-callback-invocations-proper.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From dc434e056fe1dada20df7ba07f32739d3a701adf Mon Sep 17 00:00:00 2001

From: Sebastian Andrzej Siewior <[email protected]>
Date: Tue, 14 Mar 2017 16:06:45 +0100
Subject: cpu/hotplug: Serialize callback invocations proper

From: Sebastian Andrzej Siewior <[email protected]>

commit dc434e056fe1dada20df7ba07f32739d3a701adf upstream.

The setup/remove_state/instance() functions in the hotplug core code are serialized against concurrent CPU hotplug, but unfortunately not serialized against themself.

As a consequence a concurrent invocation of these function results in corruption of the callback machinery because two instances try to invoke callbacks on remote cpus at the same time. This results in missing callback invocations and initiator threads waiting forever on the completion.

The obvious solution to replace get_cpu_online() with cpu_hotplug_begin() is not possible because at least one callsite calls into these functions from a get_online_cpu() locked region.

Extend the protection scope of the cpuhp_state_mutex from solely protecting the state arrays to cover the callback invocation machinery as well.

Fixes 5b7aa87e0482 ("cpu/hotplug: Implement setup/removal interface")

Reported-and-tested-by Bart Van Assche <[email protected]>

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

Cc [email protected]

Link http://lkml.kernel.org/r/[email protected] open here

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

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 kernel/cpu.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

kernel/cpu.c +9 -8

@@ -1441,14 +1441,12 @@ static void cpuhp_store_callbacks(enum c
 	/* (Un)Install the callbacks for further cpu hotplug operations */
 	struct cpuhp_step *sp;
 
-	mutex_lock(&cpuhp_state_mutex);
 	sp = cpuhp_get_step(state);
 	sp->startup.single = startup;
 	sp->teardown.single = teardown;
 	sp->name = name;
 	sp->multi_instance = multi_instance;
 	INIT_HLIST_HEAD(&sp->list);
-	mutex_unlock(&cpuhp_state_mutex);
 }
 
 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)

@@ -1518,16 +1516,13 @@ static int cpuhp_reserve_state(enum cpuh
 {
 	enum cpuhp_state i;
 
-	mutex_lock(&cpuhp_state_mutex);
 	for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
 		if (cpuhp_ap_states[i].name)
 			continue;
 
 		cpuhp_ap_states[i].name = "Reserved";
-		mutex_unlock(&cpuhp_state_mutex);
 		return i;
 	}
-	mutex_unlock(&cpuhp_state_mutex);
 	WARN(1, "No more dynamic states available for CPU hotplug\n");
 	return -ENOSPC;
 }

@@ -1544,6 +1539,7 @@ int __cpuhp_state_add_instance(enum cpuh
 		return -EINVAL;
 
 	get_online_cpus();
+	mutex_lock(&cpuhp_state_mutex);
 
 	if (!invoke || !sp->startup.multi)
 		goto add_node;

@@ -1568,11 +1564,10 @@ int __cpuhp_state_add_instance(enum cpuh
 	}
 add_node:
 	ret = 0;
-	mutex_lock(&cpuhp_state_mutex);
 	hlist_add_head(node, &sp->list);
-	mutex_unlock(&cpuhp_state_mutex);
 
 err:
+	mutex_unlock(&cpuhp_state_mutex);
 	put_online_cpus();
 	return ret;
 }

@@ -1601,6 +1596,7 @@ int __cpuhp_setup_state(enum cpuhp_state
 		return -EINVAL;
 
 	get_online_cpus();
+	mutex_lock(&cpuhp_state_mutex);
 
 	/* currently assignments for the ONLINE state are possible */
 	if (state == CPUHP_AP_ONLINE_DYN) {

@@ -1636,6 +1632,8 @@ int __cpuhp_setup_state(enum cpuhp_state
 		}
 	}
 out:
+	mutex_unlock(&cpuhp_state_mutex);
+
 	put_online_cpus();
 	if (!ret && dyn_state)
 		return state;

@@ -1655,6 +1653,8 @@ int __cpuhp_state_remove_instance(enum c
 		return -EINVAL;
 
 	get_online_cpus();
+	mutex_lock(&cpuhp_state_mutex);
+
 	if (!invoke || !cpuhp_get_teardown_cb(state))
 		goto remove;
 	/*

@@ -1671,7 +1671,6 @@ int __cpuhp_state_remove_instance(enum c
 	}
 
 remove:
-	mutex_lock(&cpuhp_state_mutex);
 	hlist_del(node);
 	mutex_unlock(&cpuhp_state_mutex);
 	put_online_cpus();

@@ -1696,6 +1695,7 @@ void __cpuhp_remove_state(enum cpuhp_sta
 	BUG_ON(cpuhp_cb_check(state));
 
 	get_online_cpus();
+	mutex_lock(&cpuhp_state_mutex);
 
 	if (sp->multi_instance) {
 		WARN(!hlist_empty(&sp->list),

@@ -1721,6 +1721,7 @@ void __cpuhp_remove_state(enum cpuhp_sta
 	}
 remove:
 	cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
+	mutex_unlock(&cpuhp_state_mutex);
 	put_online_cpus();
 }
 EXPORT_SYMBOL(__cpuhp_remove_state);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/cpu-hotplug-serialize-callback-invocations-proper.patch