[PATCH 34/51] zsmalloc: Fix CPU hotplug callback registration

[PATCH 34/51] zsmalloc: Fix CPU hotplug callback registration

[Srivatsa S. Bhat]

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_maps_update_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_maps_update_done();


Fix the zsmalloc code by using this latter form of callback registration.

Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: linux-mm@kvack.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 mm/zsmalloc.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index c03ca5e..6f7364c 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -814,21 +814,32 @@ static void zs_exit(void)
 {
 	int cpu;
 
+	cpu_maps_update_begin();
+
 	for_each_online_cpu(cpu)
 		zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
-	unregister_cpu_notifier(&zs_cpu_nb);
+	__unregister_cpu_notifier(&zs_cpu_nb);
+
+	cpu_maps_update_done();
 }
 
 static int zs_init(void)
 {
 	int cpu, ret;
 
-	register_cpu_notifier(&zs_cpu_nb);
+	cpu_maps_update_begin();
+
+	__register_cpu_notifier(&zs_cpu_nb);
 	for_each_online_cpu(cpu) {
 		ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
-		if (notifier_to_errno(ret))
+		if (notifier_to_errno(ret)) {
+			cpu_maps_update_done();
 			goto fail;
+		}
 	}
+
+	cpu_maps_update_done();
+
 	return 0;
 fail:
 	zs_exit();

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[PATCH 48/51] mm, vmstat: Fix CPU hotplug callback registration

[Srivatsa S. Bhat]

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_maps_update_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_maps_update_done();


Fix the vmstat code in the MM subsystem by using this latter form of callback
registration.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: linux-mm@kvack.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 mm/vmstat.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 7249614..70668ba 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1290,14 +1290,14 @@ static int __init setup_vmstat(void)
 #ifdef CONFIG_SMP
 	int cpu;
 
-	register_cpu_notifier(&vmstat_notifier);
+	cpu_maps_update_begin();
+	__register_cpu_notifier(&vmstat_notifier);
 
-	get_online_cpus();
 	for_each_online_cpu(cpu) {
 		start_cpu_timer(cpu);
 		node_set_state(cpu_to_node(cpu), N_CPU);
 	}
-	put_online_cpus();
+	cpu_maps_update_done();
 #endif
 #ifdef CONFIG_PROC_FS
 	proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);

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Re: [PATCH 48/51] mm, vmstat: Fix CPU hotplug callback registration

[Christoph Lameter]

On Thu, 6 Feb 2014, Srivatsa S. Bhat wrote:

> Fix the vmstat code in the MM subsystem by using this latter form of callback
> registration.

Acked-by: Christoph Lameter <cl@linux.com>

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Re: [PATCH 48/51] mm, vmstat: Fix CPU hotplug callback registration

[Yasuaki Ishimatsu]

(2014/02/06 7:13), Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> 	get_online_cpus();
>
> 	for_each_online_cpu(cpu)
> 		init_cpu(cpu);
>
> 	register_cpu_notifier(&foobar_cpu_notifier);
>
> 	put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> 	cpu_maps_update_begin();
>
> 	for_each_online_cpu(cpu)
> 		init_cpu(cpu);
>
> 	/* Note the use of the double underscored version of the API */
> 	__register_cpu_notifier(&foobar_cpu_notifier);
>
> 	cpu_maps_update_done();
>
>
> Fix the vmstat code in the MM subsystem by using this latter form of callback
> registration.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
> Cc: Toshi Kani <toshi.kani@hp.com>
> Cc: Dave Hansen <dave@sr71.net>
> Cc: linux-mm@kvack.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---

Looks good to me.

Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>

Thanks,
Yasuaki Ishimatsu


>
>   mm/vmstat.c |    6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 7249614..70668ba 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1290,14 +1290,14 @@ static int __init setup_vmstat(void)
>   #ifdef CONFIG_SMP
>   	int cpu;
>
> -	register_cpu_notifier(&vmstat_notifier);
> +	cpu_maps_update_begin();
> +	__register_cpu_notifier(&vmstat_notifier);
>
> -	get_online_cpus();
>   	for_each_online_cpu(cpu) {
>   		start_cpu_timer(cpu);
>   		node_set_state(cpu_to_node(cpu), N_CPU);
>   	}
> -	put_online_cpus();
> +	cpu_maps_update_done();
>   #endif
>   #ifdef CONFIG_PROC_FS
>   	proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
>


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[PATCH 49/51] mm, zswap: Fix CPU hotplug callback registration

[Srivatsa S. Bhat]

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_maps_update_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_maps_update_done();


Fix the zswap code by using this latter form of callback registration.

Cc: linux-mm@kvack.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 mm/zswap.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index e55bab9..681fa3f 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -387,18 +387,18 @@ static int zswap_cpu_init(void)
 {
 	unsigned long cpu;
 
-	get_online_cpus();
+	cpu_maps_update_begin();
 	for_each_online_cpu(cpu)
 		if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
 			goto cleanup;
-	register_cpu_notifier(&zswap_cpu_notifier_block);
-	put_online_cpus();
+	__register_cpu_notifier(&zswap_cpu_notifier_block);
+	cpu_maps_update_done();
 	return 0;
 
 cleanup:
 	for_each_online_cpu(cpu)
 		__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
-	put_online_cpus();
+	cpu_maps_update_done();
 	return -ENOMEM;
 }
 

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