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

Rafael J. Wysocki
2007-07-03T22:33:15Z

On Tuesday, 3 July 2007 23:35, Benjamin Herrenschmidt wrote:
>
> > I don't think that would matter.
> >
> > Still, I can remove the sync from the suspend code path only, leaving it in
> > the hibernation code path. The patch will be bigger, but well.
> >
> > Any objection to that?
>
> Makes sense to sync before suspend tho, to limit the amount of dirty
> non-written pages in case things go wrong.

OK, below is the updated patch.

Greetings,
Rafael

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

The syncing of filesystems from within the freezer in not needed for suspend to
RAM and leads to problems with FUSE. Change freeze_processes() so that it
doesn't execute sys_sync() and introduce the "syncing" version of it to be
called from the hibernation code paths.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
include/linux/freezer.h | 14 ++++++++++++--
kernel/power/disk.c | 2 +-
kernel/power/main.c | 6 ++++++
kernel/power/process.c | 8 +++++---
kernel/power/user.c | 2 +-
5 files changed, 25 insertions(+), 7 deletions(-)

Index: linux-2.6.22-rc7/include/linux/freezer.h
===================================================================
--- linux-2.6.22-rc7.orig/include/linux/freezer.h 2007-07-04 00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/include/linux/freezer.h 2007-07-04 00:22:37.000000000 +0200
@@ -62,7 +62,7 @@ static inline int thaw_process(struct ta
}

extern void refrigerator(void);
-extern int freeze_processes(void);
+extern int __freeze_processes(int sync_filesystems);
extern void thaw_processes(void);

static inline int try_to_freeze(void)
@@ -134,7 +134,7 @@ static inline void clear_freeze_flag(str
static inline int thaw_process(struct task_struct *p) { return 1; }

static inline void refrigerator(void) {}
-static inline int freeze_processes(void) { BUG(); return 0; }
+static inline int __freeze_processes(int s) { BUG(); return 0; }
static inline void thaw_processes(void) {}

static inline int try_to_freeze(void) { return 0; }
@@ -145,4 +145,14 @@ static inline int freezer_should_skip(st
static inline void set_freezable(void) {}
#endif

+static inline int freeze_processes(void)
+{
+ return __freeze_processes(0);
+}
+
+static inline int freeze_processes_with_sync(void)
+{
+ return __freeze_processes(1);
+}
+
#endif /* FREEZER_H_INCLUDED */
Index: linux-2.6.22-rc7/kernel/power/disk.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/disk.c 2007-07-04 00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/kernel/power/disk.c 2007-07-04 00:21:44.000000000 +0200
@@ -281,7 +281,7 @@ static int prepare_processes(void)
int error = 0;

pm_prepare_console();
- if (freeze_processes()) {
+ if (freeze_processes_with_sync()) {
error = -EBUSY;
unprepare_processes();
}
Index: linux-2.6.22-rc7/kernel/power/main.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/main.c 2007-07-04 00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/kernel/power/main.c 2007-07-04 00:23:40.000000000 +0200
@@ -20,6 +20,7 @@
#include <linux/resume-trace.h>
#include <linux/freezer.h>
#include <linux/vmstat.h>
+#include <linux/syscalls.h>

#include "power.h"

@@ -231,6 +232,11 @@ static int enter_state(suspend_state_t s

if (!valid_state(state))
return -ENODEV;
+
+ printk("Syncing filesystems ... ");
+ sys_sync();
+ printk("done.\n");
+
if (!mutex_trylock(&pm_mutex))
return -EBUSY;

Index: linux-2.6.22-rc7/kernel/power/process.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/process.c 2007-07-04 00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/kernel/power/process.c 2007-07-04 00:21:44.000000000 +0200
@@ -179,9 +179,9 @@ static int try_to_freeze_tasks(int freez
}

/**
- * freeze_processes - tell processes to enter the refrigerator
+ * __freeze_processes - tell processes to enter the refrigerator
*/
-int freeze_processes(void)
+int __freeze_processes(int sync_filesystems)
{
int error;

@@ -190,7 +190,9 @@ int freeze_processes(void)
if (error)
return error;

- sys_sync();
+ if (sync_filesystems)
+ sys_sync();
+
error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
if (error)
return error;
Index: linux-2.6.22-rc7/kernel/power/user.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/user.c 2007-07-04 00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/kernel/power/user.c 2007-07-04 00:21:44.000000000 +0200
@@ -153,7 +153,7 @@ static int snapshot_ioctl(struct inode *
mutex_lock(&pm_mutex);
error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
if (!error) {
- error = freeze_processes();
+ error = freeze_processes_with_sync();
if (error)
thaw_processes();
}