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Date: Sun, 09 Oct 2011 01:58:04 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Américo Wang <xiyou.wangcong@...il.com>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
"Rafael J. Wysocki" <rjw@...k.pl>, pavel@....cz,
len.brown@...el.com, mingo@...e.hu, akpm@...ux-foundation.org,
suresh.b.siddha@...el.com, lucas.demarchi@...fusion.mobi,
Linux PM mailing list <linux-pm@...r.kernel.org>,
rusty@...tcorp.com.au, vatsa@...ux.vnet.ibm.com,
ashok.raj@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] CPU hotplug, freezer: Fix bugs in CPU hotplug call
path
On 10/08/2011 06:22 PM, Américo Wang wrote:
> On Sat, Oct 8, 2011 at 4:56 AM, Srivatsa S. Bhat
> <srivatsa.bhat@...ux.vnet.ibm.com> wrote:
>> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
>> index 1effc8b..75c65d6 100644
>> --- a/include/linux/freezer.h
>> +++ b/include/linux/freezer.h
>> @@ -7,6 +7,9 @@
>> #include <linux/wait.h>
>>
>> #ifdef CONFIG_FREEZER
>> +
>> +extern struct mutex freezer_lock;
>> +
> [...]
>> static inline int try_to_freeze(void)
>> {
>> if (freezing(current)) {
>> diff --git a/kernel/cpu.c b/kernel/cpu.c
>> index 12b7458..b94c8f6 100644
>> --- a/kernel/cpu.c
>> +++ b/kernel/cpu.c
>> @@ -15,6 +15,7 @@
>> #include <linux/stop_machine.h>
>> #include <linux/mutex.h>
>> #include <linux/gfp.h>
>> +#include <linux/freezer.h>
>>
>> #ifdef CONFIG_SMP
>> /* Serializes the updates to cpu_online_mask, cpu_present_mask */
>> @@ -280,7 +281,9 @@ int __ref cpu_down(unsigned int cpu)
>> goto out;
>> }
>>
>> - err = _cpu_down(cpu, 0);
>> + mutex_lock(&freezer_lock);
>> + err = _cpu_down(cpu, tasks_are_frozen());
>> + mutex_unlock(&freezer_lock);
>>
>
> Can this even be compiled when CONFIG_FREEZER=n?
>
Oh! That's a mistake.. Thank you for pointing it out.
This one should fix it:
---
include/linux/freezer.h | 22 ++++++++++++++++++++++
kernel/cpu.c | 9 +++++++--
kernel/power/process.c | 27 ++++++++++++++++++++++++++-
3 files changed, 55 insertions(+), 3 deletions(-)
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index 1effc8b..3d80ddb 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -7,6 +7,19 @@
#include <linux/wait.h>
#ifdef CONFIG_FREEZER
+
+extern struct mutex freezer_lock;
+
+static inline void lock_freezer(void)
+{
+ mutex_lock(&freezer_lock);
+}
+
+static inline void unlock_freezer(void)
+{
+ mutex_unlock(&freezer_lock);
+}
+
/*
* Check if a process has been frozen
*/
@@ -51,6 +64,10 @@ extern void refrigerator(void);
extern int freeze_processes(void);
extern void thaw_processes(void);
+extern void set_tasks_frozen_flag(void);
+extern void clear_tasks_frozen_flag(void);
+extern int tasks_are_frozen(void);
+
static inline int try_to_freeze(void)
{
if (freezing(current)) {
@@ -164,6 +181,8 @@ static inline void set_freezable_with_signal(void)
__retval; \
})
#else /* !CONFIG_FREEZER */
+static inline void lock_freezer(void) {}
+static inline void unlock_freezer(void) {}
static inline int frozen(struct task_struct *p) { return 0; }
static inline int freezing(struct task_struct *p) { return 0; }
static inline void set_freeze_flag(struct task_struct *p) {}
@@ -173,6 +192,9 @@ static inline int thaw_process(struct task_struct *p) { return 1; }
static inline void refrigerator(void) {}
static inline int freeze_processes(void) { BUG(); return 0; }
static inline void thaw_processes(void) {}
+static inline void set_tasks_frozen_flag(void) {}
+static inline void clear_tasks_frozen_flag(void) {}
+static inline int tasks_are_frozen(void) { return 0; }
static inline int try_to_freeze(void) { return 0; }
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 12b7458..d81ceea 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -15,6 +15,7 @@
#include <linux/stop_machine.h>
#include <linux/mutex.h>
#include <linux/gfp.h>
+#include <linux/freezer.h>
#ifdef CONFIG_SMP
/* Serializes the updates to cpu_online_mask, cpu_present_mask */
@@ -280,7 +281,9 @@ int __ref cpu_down(unsigned int cpu)
goto out;
}
- err = _cpu_down(cpu, 0);
+ lock_freezer();
+ err = _cpu_down(cpu, tasks_are_frozen());
+ unlock_freezer();
out:
cpu_maps_update_done();
@@ -373,7 +376,9 @@ int __cpuinit cpu_up(unsigned int cpu)
goto out;
}
- err = _cpu_up(cpu, 0);
+ lock_freezer();
+ err = _cpu_up(cpu, tasks_are_frozen());
+ unlock_freezer();
out:
cpu_maps_update_done();
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 0cf3a27..9da3369 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -17,11 +17,30 @@
#include <linux/delay.h>
#include <linux/workqueue.h>
-/*
+/*
* Timeout for stopping processes
*/
#define TIMEOUT (20 * HZ)
+DEFINE_MUTEX(freezer_lock);
+
+static int tasks_frozen;
+
+void set_tasks_frozen_flag(void)
+{
+ tasks_frozen = 1;
+}
+
+void clear_tasks_frozen_flag(void)
+{
+ tasks_frozen = 0;
+}
+
+int tasks_are_frozen(void)
+{
+ return tasks_frozen;
+}
+
static inline int freezable(struct task_struct * p)
{
if ((p == current) ||
@@ -141,6 +160,7 @@ int freeze_processes(void)
{
int error;
+ lock_freezer();
printk("Freezing user space processes ... ");
error = try_to_freeze_tasks(true);
if (error)
@@ -151,10 +171,12 @@ int freeze_processes(void)
error = try_to_freeze_tasks(false);
if (error)
goto Exit;
+ set_tasks_frozen_flag();
printk("done.");
oom_killer_disable();
Exit:
+ unlock_freezer();
BUG_ON(in_atomic());
printk("\n");
@@ -183,6 +205,7 @@ static void thaw_tasks(bool nosig_only)
void thaw_processes(void)
{
+ lock_freezer();
oom_killer_enable();
printk("Restarting tasks ... ");
@@ -190,6 +213,8 @@ void thaw_processes(void)
thaw_tasks(true);
thaw_tasks(false);
schedule();
+ clear_tasks_frozen_flag();
+ unlock_freezer();
printk("done.\n");
}
--
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