[PATCH v3] cpu/hotplug: handle unbalanced hotplug enable/disable

[PATCH v3] cpu/hotplug: handle unbalanced hotplug enable/disable

[Lianwei Wang]

Currently it just print a warning message but did not
reset cpu_hotplug_disabled when the enable/disable is
unbalanced. The unbalanced enable/disable will lead
the cpu hotplug work abnormally.

Do nothing if an unablanced hotplug enable detected.

Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>
---
 kernel/cpu.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3e3f6e49eabb..5e26a3c64934 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -245,6 +245,14 @@ void cpu_hotplug_done(void)
 	cpuhp_lock_release();
 }
 
+static void __cpu_hotplug_enable(void)
+{
+	if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
+		return;
+
+	cpu_hotplug_disabled--;
+}
+
 /*
  * Wait for currently running CPU hotplug operations to complete (if any) and
  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
@@ -263,7 +271,7 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 void cpu_hotplug_enable(void)
 {
 	cpu_maps_update_begin();
-	WARN_ON(--cpu_hotplug_disabled < 0);
+	__cpu_hotplug_enable();
 	cpu_maps_update_done();
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
@@ -1091,7 +1099,7 @@ void enable_nonboot_cpus(void)
 
 	/* Allow everyone to use the CPU hotplug again */
 	cpu_maps_update_begin();
-	WARN_ON(--cpu_hotplug_disabled < 0);
+	__cpu_hotplug_enable();
 	if (cpumask_empty(frozen_cpus))
 		goto out;
 
-- 
1.9.1

Re: [PATCH v3] cpu/hotplug: handle unbalanced hotplug enable/disable

[Lianwei Wang]

On Thu, Jun 9, 2016 at 11:43 PM, Lianwei Wang <lianwei.wang@gmail.com> wrote:
> Currently it just print a warning message but did not
> reset cpu_hotplug_disabled when the enable/disable is
> unbalanced. The unbalanced enable/disable will lead
> the cpu hotplug work abnormally.
>
> Do nothing if an unablanced hotplug enable detected.
>
> Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>
> ---
>  kernel/cpu.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 3e3f6e49eabb..5e26a3c64934 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -245,6 +245,14 @@ void cpu_hotplug_done(void)
>         cpuhp_lock_release();
>  }
>
> +static void __cpu_hotplug_enable(void)
> +{
> +       if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
> +               return;
> +
> +       cpu_hotplug_disabled--;
> +}
> +
>  /*
>   * Wait for currently running CPU hotplug operations to complete (if any) and
>   * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
> @@ -263,7 +271,7 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
>  void cpu_hotplug_enable(void)
>  {
>         cpu_maps_update_begin();
> -       WARN_ON(--cpu_hotplug_disabled < 0);
> +       __cpu_hotplug_enable();
>         cpu_maps_update_done();
>  }
>  EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
> @@ -1091,7 +1099,7 @@ void enable_nonboot_cpus(void)
>
>         /* Allow everyone to use the CPU hotplug again */
>         cpu_maps_update_begin();
> -       WARN_ON(--cpu_hotplug_disabled < 0);
> +       __cpu_hotplug_enable();
>         if (cpumask_empty(frozen_cpus))
>                 goto out;
>
> --
> 1.9.1
>

Hi Thomas Gleixner,

Does this change look good to you?

[tip:smp/hotplug] cpu/hotplug: Handle unbalanced hotplug enable/disable

[tip-bot for Lianwei Wang]

Commit-ID:  01b41159066531cc8d664362ff0cd89dd137bbfa
Gitweb:     http://git.kernel.org/tip/01b41159066531cc8d664362ff0cd89dd137bbfa
Author:     Lianwei Wang <lianwei.wang@gmail.com>
AuthorDate: Thu, 9 Jun 2016 23:43:28 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 2 Sep 2016 20:37:17 +0200

cpu/hotplug: Handle unbalanced hotplug enable/disable

When cpu_hotplug_enable() is called unbalanced w/o a preceeding
cpu_hotplug_disable() the code emits a warning, but happily decrements the
disabled counter. This causes the next operations to malfunction.

Prevent the decrement and just emit a warning.

Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>
Cc: peterz@infradead.org
Cc: linux-pm@vger.kernel.org
Cc: oleg@redhat.com
Link: http://lkml.kernel.org/r/1465541008-12476-1-git-send-email-lianwei.wang@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 kernel/cpu.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index c506485..c90f839 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -331,10 +331,17 @@ void cpu_hotplug_disable(void)
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 
+static void __cpu_hotplug_enable(void)
+{
+	if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
+		return;
+	cpu_hotplug_disabled--;
+}
+
 void cpu_hotplug_enable(void)
 {
 	cpu_maps_update_begin();
-	WARN_ON(--cpu_hotplug_disabled < 0);
+	__cpu_hotplug_enable();
 	cpu_maps_update_done();
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
@@ -1160,7 +1167,7 @@ void enable_nonboot_cpus(void)
 
 	/* Allow everyone to use the CPU hotplug again */
 	cpu_maps_update_begin();
-	WARN_ON(--cpu_hotplug_disabled < 0);
+	__cpu_hotplug_enable();
 	if (cpumask_empty(frozen_cpus))
 		goto out;