linux-kernel - Re: [PATCH] Remove process freezer from suspend to RAM pathway

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Date:	Tue, 3 Jul 2007 17:09:29 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Pavel Machek <pavel@....cz>,
	Nigel Cunningham <nigel@...el.suspend2.net>
Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway

On Tuesday, 3 July 2007 15:08, Rafael J. Wysocki wrote:
> On Tuesday, 3 July 2007 07:51, Benjamin Herrenschmidt wrote:
> > On Tue, 2007-07-03 at 05:29 +0100, Matthew Garrett wrote:
> > > Suspend to RAM on a machine with / on a fuse filesystem turns out to be 
> > > a screaming nightmare - either the suspend fails because syslog (for 
> > > instance) can't be frozen, or the machine deadlocks for some other 
> > > reason I haven't tracked down. We could "fix" fuse, or alternatively we 
> > > could do what we do for suspend to RAM on other platforms (PPC and APM) 
> > > and just not use the freezer.
> > 
> > The main reason for deadlocks is because we do a sys_sync() after the
> > freeze, which we shouldn't do.
> 
> So why don't we remove the sys_sync() from freeze_processes() instead?

The patch follows (untested).

Greetings,
Rafael


---
From: Rafael J. Wysocki <rjw@...k.pl>

We shouldn't sync filesystems from within the freezer, because it's not needed
for suspend to RAM and leads to problems with FUSE.

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
 kernel/power/disk.c    |    4 ++++
 kernel/power/process.c |    1 -
 2 files changed, 4 insertions(+), 1 deletion(-)

Index: linux-2.6.22-rc7/kernel/power/disk.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/disk.c
+++ linux-2.6.22-rc7/kernel/power/disk.c
@@ -296,6 +296,10 @@ int hibernate(void)
 {
 	int error;
 
+	printk("Syncing filesystems ... \n");
+	sys_sync();
+	printk("done.\n");
+
 	mutex_lock(&pm_mutex);
 	/* The snapshot device should not be opened while we're running */
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
Index: linux-2.6.22-rc7/kernel/power/process.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/process.c
+++ linux-2.6.22-rc7/kernel/power/process.c
@@ -190,7 +190,6 @@ int freeze_processes(void)
 	if (error)
 		return error;
 
-	sys_sync();
 	error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 	if (error)
 		return error;
-
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