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Message-ID: <alpine.LSU.2.00.1011301333380.11072@tigran.mtv.corp.google.com>
Date: Tue, 30 Nov 2010 14:16:25 -0800 (PST)
From: Hugh Dickins <hughd@...gle.com>
To: "Rafael J. Wysocki" <rjw@...k.pl>
cc: Ondrej Zary <linux@...nbow-software.org>,
Andrew Morton <akpm@...ux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Kernel development list <linux-kernel@...r.kernel.org>,
Balbir Singh <balbir@...ibm.com>
Subject: Re: 2.6.35.5: hibernation broken... AGAIN
On Sat, 27 Nov 2010, Rafael J. Wysocki wrote:
> On Saturday, November 27, 2010, Ondrej Zary wrote:
> > > > >
> > > > > Not signing it off yet,
> > > > > Hugh
> > > >
> > > > Could you please do that? The patch fixes the problem.
Sorry for going quiet for so long.
Thanks for testing, Ondrej. I completely agree with Rafael that my
patch was inadequate: it turned out to be good enough for your useful
feedback on the main path through hibernation, but missed a number
of details. We do need something like Rafael's patch - thanks.
(And I realize that it's tiresome and frustrating for you to be
trying first that and then this etc; but we had bugs here precisely
because this is a confusing area, so I think it is worth some effort
to get right now.)
> > >
> > > Can you check if the problem is also fixed by the patch below, please?
> >
> > The patch does not apply to 2.6.35.4, 2.6.35.5 and also 2.6.36. What version
> > should I test?
>
> The patch was against the current mainline.
>
> The one below was rebased on top of 2.6.36, so please test it with this kernel.
I'll comment on this version, since it has one more line than your original.
>
> Thanks,
> Rafael
>
> ---
> kernel/power/hibernate.c | 36 ++++++++++++++++++++++++++----------
> kernel/power/power.h | 1 +
> kernel/power/user.c | 2 ++
> 3 files changed, 29 insertions(+), 10 deletions(-)
>
> Index: suspend-2.6/kernel/power/hibernate.c
> ===================================================================
> --- suspend-2.6.orig/kernel/power/hibernate.c
> +++ suspend-2.6/kernel/power/hibernate.c
> @@ -29,6 +29,21 @@
> #include "power.h"
>
>
> +static gfp_t saved_gfp_mask;
> +
> +static void hibernate_restrict_gfp_mask(void)
> +{
> + saved_gfp_mask = clear_gfp_allowed_mask(GFP_IOFS);
> +}
> +
> +void hibernate_restore_gfp_mask(void)
> +{
> + if (saved_gfp_mask) {
> + set_gfp_allowed_mask(saved_gfp_mask);
> + saved_gfp_mask = 0;
> + }
> +}
> +
Trivial point, I suppose, but it bothers me that PM is accumulating
wrappers around wrappers around gfp_allowed_mask. Looks like
clear_gfp_allowed_mask and set_gfp_allowed_mask (oddly asymmetrical)
were not really what we need. How about scrapping them, and putting
pm_restrict_gfp_mask() and pm_restore_gfp_mask() into page_alloc.c?
> static int noresume = 0;
> static char resume_file[256] = CONFIG_PM_STD_PARTITION;
> dev_t swsusp_resume_device;
> @@ -326,7 +341,6 @@ static int create_image(int platform_mod
> int hibernation_snapshot(int platform_mode)
> {
> int error;
> - gfp_t saved_mask;
>
> error = platform_begin(platform_mode);
> if (error)
> @@ -338,7 +352,7 @@ int hibernation_snapshot(int platform_mo
> goto Close;
>
> suspend_console();
> - saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
> + hibernate_restrict_gfp_mask();
Yes.
> error = dpm_suspend_start(PMSG_FREEZE);
> if (error)
> goto Recover_platform;
> @@ -347,7 +361,10 @@ int hibernation_snapshot(int platform_mo
> goto Recover_platform;
>
> error = create_image(platform_mode);
> - /* Control returns here after successful restore */
> + /*
> + * 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. */
> @@ -356,7 +373,10 @@ int hibernation_snapshot(int platform_mo
>
> dpm_resume_end(in_suspend ?
> (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
> - set_gfp_allowed_mask(saved_mask);
> +
> + if (error || !in_suspend)
> + hibernate_restore_gfp_mask();
> +
I'm worried that it's hard to find and maintain the places that need
this restoration - and if we miss one, we won't find out about it for
ages. It would help a lot if the gfp restoration always accompanies
some other essential stage - thaw_processes() looks to be right,
so could we skip conditionally restoring here if we do it then?
I suggest that in part because I cannot find where you restore in
the case that hibernate()'s swsusp_write() fails - that was the
case that made me realize my little patch was too simplistic.
> resume_console();
> Close:
> platform_end(platform_mode);
> @@ -451,17 +471,16 @@ static int resume_target_kernel(bool pla
> int hibernation_restore(int platform_mode)
> {
> int error;
> - gfp_t saved_mask;
>
> pm_prepare_console();
> suspend_console();
> - saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
> + hibernate_restrict_gfp_mask();
Yes.
> error = dpm_suspend_start(PMSG_QUIESCE);
> if (!error) {
> error = resume_target_kernel(platform_mode);
> dpm_resume_end(PMSG_RECOVER);
> }
> - set_gfp_allowed_mask(saved_mask);
> + hibernate_restore_gfp_mask();
But this could be left until software_resume()'s thaw_processes()?
Ah, that won't cover the SNAPSHOT_ATOMIC_RESTORE case, hmmm.
> resume_console();
> pm_restore_console();
> return error;
> @@ -475,7 +494,6 @@ int hibernation_restore(int platform_mod
> int hibernation_platform_enter(void)
> {
> int error;
> - gfp_t saved_mask;
>
> if (!hibernation_ops)
> return -ENOSYS;
> @@ -491,7 +509,6 @@ int hibernation_platform_enter(void)
>
> entering_platform_hibernation = true;
> suspend_console();
> - saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
Right.
> error = dpm_suspend_start(PMSG_HIBERNATE);
> if (error) {
> if (hibernation_ops->recover)
> @@ -535,7 +552,6 @@ int hibernation_platform_enter(void)
> Resume_devices:
> entering_platform_hibernation = false;
> dpm_resume_end(PMSG_RESTORE);
> - set_gfp_allowed_mask(saved_mask);
Right.
> resume_console();
>
> Close:
> Index: suspend-2.6/kernel/power/power.h
> ===================================================================
> --- suspend-2.6.orig/kernel/power/power.h
> +++ suspend-2.6/kernel/power/power.h
> @@ -49,6 +49,7 @@ static inline char *check_image_kernel(s
> extern int hibernation_snapshot(int platform_mode);
> extern int hibernation_restore(int platform_mode);
> extern int hibernation_platform_enter(void);
> +extern void hibernate_restore_gfp_mask(void);
> #endif
>
> extern int pfn_is_nosave(unsigned long);
> Index: suspend-2.6/kernel/power/user.c
> ===================================================================
> --- suspend-2.6.orig/kernel/power/user.c
> +++ suspend-2.6/kernel/power/user.c
> @@ -263,6 +263,7 @@ static long snapshot_ioctl(struct file *
> case SNAPSHOT_UNFREEZE:
> if (!data->frozen || data->ready)
> break;
> + hibernate_restore_gfp_mask();
Right, here you have one next to thaw_processes().
But the SNAPSHOT ioctls are a nightmarish maze to me,
I cannot comment much on what's right here.
> thaw_processes();
> usermodehelper_enable();
> data->frozen = 0;
> @@ -275,6 +276,7 @@ static long snapshot_ioctl(struct file *
> error = -EPERM;
> break;
> }
> + hibernate_restore_gfp_mask();
> error = hibernation_snapshot(data->platform_support);
That might be good safety, but it does strongly suggest that you
needed to put it somewhere else, and couldn't work out where?
> if (!error)
> error = put_user(in_suspend, (int __user *)arg);
>
Hugh
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