linux-kernel - Re: [PATCH] PM / Hibernate: Thaw processes in SNAPSHOT_CREATE

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Message-ID: <4ED7AB26.4080804@linux.vnet.ibm.com>
Date:	Thu, 01 Dec 2011 21:58:22 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Tejun Heo <tj@...nel.org>
CC:	rjw@...k.pl, pavel@....cz, len.brown@...el.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH] PM / Hibernate: Thaw processes in SNAPSHOT_CREATE_IMAGE
 ioctl error/test paths

On 12/01/2011 09:17 PM, Tejun Heo wrote:

> On Thu, Dec 01, 2011 at 06:45:37PM +0530, Srivatsa S. Bhat wrote:
>> Commit 2aede851ddf08666f68ffc17be446420e9d2a056 (PM / Hibernate: Freeze
>> kernel threads after preallocating memory) moved the freezing of kernel
>> threads to hibernation_snapshot() function.
>>
>> So now, if the call to hibernation_snapshot() fails or returns early due
>> to a successful hibernation test, the caller has to thaw processes to
>> ensure that the system gets back to its original state.
>>
>> But in SNAPSHOT_CREATE_IMAGE hibernation ioctl, the caller does not thaw
>> processes. Fix this issue. But note that if hibernation_snapshot() returned
>> due to a successful freezer test, we still send the value of 'in_suspend'
>> (which is now 0) to userspace, because we are not in an error path per-se,
>> and moreover, the value of in_suspend correctly depicts the situation here.
>>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> 
> Is this still applicable on top of pm-freezer branch?
> 


Well, yes, but not in this form. Thanks for bringing that up!

If the call to hibernation_snapshot() returns an error, we need not do
anything since your freezer changes handle that case and call thaw_processes()
automatically.
But in case of return due to a successful freezer test, we would need to
explicitly thaw processes since the freezer successfully froze them in the
previous step.

So the following patch would do that, for the pm-freezer branch:

---
From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: [PATCH] PM / Hibernate: Thaw processes in SNAPSHOT_CREATE_IMAGE ioctl test path

Commit 2aede851ddf08666f68ffc17be446420e9d2a056 (PM / Hibernate: Freeze
kernel threads after preallocating memory) moved the freezing of kernel
threads to hibernation_snapshot() function.

So now, if the call to hibernation_snapshot() returns early due to a
successful hibernation test, the caller has to thaw processes to ensure
that the system gets back to its original state.

But in SNAPSHOT_CREATE_IMAGE hibernation ioctl, the caller does not thaw
processes in case hibernation_snapshot() returned due to a successful
freezer test. Fix this issue. But note we still send the value of 'in_suspend'
(which is now 0) to userspace, because we are not in an error path per-se,
and moreover, the value of in_suspend correctly depicts the situation here.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---

 kernel/power/hibernate.c |    2 +-
 kernel/power/power.h     |    2 ++
 kernel/power/user.c      |   11 ++++++++---
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 80c2d90..57bab63 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -55,7 +55,7 @@ enum {
 
 static int hibernation_mode = HIBERNATION_SHUTDOWN;
 
-static bool freezer_test_done;
+bool freezer_test_done;
 
 static const struct platform_hibernation_ops *hibernation_ops;
 
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 23a2db1..0c4defe 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -50,6 +50,8 @@ static inline char *check_image_kernel(struct swsusp_info *info)
 #define SPARE_PAGES	((1024 * 1024) >> PAGE_SHIFT)
 
 /* kernel/power/hibernate.c */
+extern bool freezer_test_done;
+
 extern int hibernation_snapshot(int platform_mode);
 extern int hibernation_restore(int platform_mode);
 extern int hibernation_platform_enter(void);
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 7cc3f5b..c202e2e 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -281,10 +281,15 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 		}
 		pm_restore_gfp_mask();
 		error = hibernation_snapshot(data->platform_support);
-		if (!error)
+		if (!error) {
 			error = put_user(in_suspend, (int __user *)arg);
-		if (!error)
-			data->ready = 1;
+			if (!error && !freezer_test_done)
+				data->ready = 1;
+			if (freezer_test_done) {
+				freezer_test_done = false;
+				thaw_processes();
+			}
+		}
 		break;
 
 	case SNAPSHOT_ATOMIC_RESTORE:


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