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

Rafael J. Wysocki
2007-07-03T15:02:22Z

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@sisk.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@sisk.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;