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Message-ID: <4ECBF271.3040308@linux.vnet.ibm.com>
Date: Wed, 23 Nov 2011 00:35:21 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Pavel Machek <pavel@....cz>
CC: "Rafael J. Wysocki" <rjw@...k.pl>, len.brown@...el.com,
tj@...nel.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: Re: [PATCH] PM / Hibernation: Fix *massive* memory leak at early
exits in hibernation
On 11/22/2011 05:15 PM, Pavel Machek wrote:
> On Mon 2011-11-21 23:25:39, Rafael J. Wysocki wrote:
>> On Monday, November 21, 2011, Srivatsa S. Bhat wrote:
>>> At some of the early exit points during hibernation (exiting either due
>>> to failure or after a successful hibernation test, the memory pre-allocated
>>> for hibernation is not freed up. And this is *very* serious, because, during
>>> pre-allocation, it could have allocated upto a few *gigabytes* of memory!
>>> And hence, if a hibernation fails or even if we run some hibernation tests
>>> using the 'pm_test' framework, the system is rendered unstable due to memory
>>> becoming signifantly lower. Fix this bug.
>>
>> While the observation is valid, I'd prefer to do something like the patch
>> below.
>
> The code slowly becomes goto maze :-(.
>
I agree.. It is already quite a mess.
>> @@ -357,12 +357,14 @@ int hibernation_snapshot(int platform_mo
>> * successful freezer test.
>> */
>> freezer_test_done = true;
>> - goto Close;
>> + goto Cleanup;
>> }
>>
>> error = dpm_prepare(PMSG_FREEZE);
>> - if (error)
>> - goto Complete_devices;
>> + if (error) {
>> + dpm_complete(msg);
>> + goto Cleanup;
>> + }
>
> Perhaps dpm_prepare should be changed to clean after itself in the
> error case? That is the normal convention AFAICT....
>
If the intention here is to merely clean up hibernation_snapshot() code,
I would not prefer to change the behaviour of dpm_prepare(), considering
things like, what parameter should we pass to dpm_complete(); is the
resultant behaviour change in dpm_suspend_start() correct or not; what
happens to all the code that uses the nice pair: dpm_suspend_start() and
dpm_resume_end() and so on.
Perhaps there are bigger issues involved there, since I observed on a brief
look that the current code doesn't seem to strictly follow the above
convention that whoever called dpm_prepare() should call dpm_complete()
upon failure. Or may be its doing the right thing.. I don't know.
But anyway, the good news is, even without changing dpm_prepare()'s
behaviour, we can clean up quite a bit of code in hibernation_snapshot(),
as it is.
The first patch below does the cleanup, the second patch fixes the memory
leak and applies on top of the first patch.
---
From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: PM / Hibernation: Refactor and simplify hibernation_snapshot() code
The goto statements in hibernation_snapshot() are a bit complex.
Refactor the code to remove some of them, thereby simplifying the
implementation.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---
kernel/power/hibernate.c | 28 ++++++++++++----------------
1 files changed, 12 insertions(+), 16 deletions(-)
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 196c0126..fe7e83e 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -333,7 +333,7 @@ static int create_image(int platform_mode)
*/
int hibernation_snapshot(int platform_mode)
{
- pm_message_t msg = PMSG_RECOVER;
+ pm_message_t msg;
int error;
error = platform_begin(platform_mode);
@@ -361,25 +361,27 @@ int hibernation_snapshot(int platform_mode)
}
error = dpm_prepare(PMSG_FREEZE);
- if (error)
- goto Complete_devices;
+ if (error) {
+ dpm_complete(PMSG_RECOVER);
+ goto Close;
+ }
suspend_console();
pm_restrict_gfp_mask();
+
error = dpm_suspend(PMSG_FREEZE);
- if (error)
- goto Recover_platform;
- if (hibernation_test(TEST_DEVICES))
- goto Recover_platform;
+ if (error || hibernation_test(TEST_DEVICES))
+ platform_recover(platform_mode);
+ else
+ error = create_image(platform_mode);
- error = create_image(platform_mode);
/*
- * Control returns here (1) after the image has been created or the
+ * In the case that we call create_image() above, the control
+ * returns here (1) after the image has been created or the
* image creation has failed and (2) after a successful restore.
*/
- Resume_devices:
/* We may need to release the preallocated image pages here. */
if (error || !in_suspend)
swsusp_free();
@@ -392,16 +394,10 @@ int hibernation_snapshot(int platform_mode)
resume_console();
- Complete_devices:
- dpm_complete(msg);
-
Close:
platform_end(platform_mode);
return error;
- Recover_platform:
- platform_recover(platform_mode);
- goto Resume_devices;
}
/**
==============================================
The second patch:
---
From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: PM / Hibernation: Fix memory leak in hibernation at error/test paths
At some points in the hibernation code, if we exit early either due to an
error or a successful hibernation test, the memory pre-allocated for
hibernation is not freed up, which might be quite significant. Fix this
memory leak.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---
kernel/power/hibernate.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index fe7e83e..7aea7e5 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -347,7 +347,7 @@ int hibernation_snapshot(int platform_mode)
error = freeze_kernel_threads();
if (error)
- goto Close;
+ goto Free_mem;
if (hibernation_test(TEST_FREEZER) ||
hibernation_testmode(HIBERNATION_TESTPROC)) {
@@ -357,13 +357,13 @@ int hibernation_snapshot(int platform_mode)
* successful freezer test.
*/
freezer_test_done = true;
- goto Close;
+ goto Free_mem;
}
error = dpm_prepare(PMSG_FREEZE);
if (error) {
dpm_complete(PMSG_RECOVER);
- goto Close;
+ goto Free_mem;
}
suspend_console();
@@ -398,6 +398,9 @@ int hibernation_snapshot(int platform_mode)
platform_end(platform_mode);
return error;
+ Free_mem:
+ swsusp_free();
+ goto Close;
}
/**
--
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