Re: [RFC][PATCH -mm][Experimental] swsusp: freeze userspace processes first

Pavel Machek
2006-02-01T11:47:17Z

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Hi!

> This is an experimantal patch aimed at the "unable to freeze processes under
> load" problem.
>
> On my box the 2.6.16-rc1-mm4 kernel with this patch applied survives the
> "dd if=/dev/hda of=/dev/null" test.
>
> Please have a look.

It makes it better (well, I used my own, simpler variant, but that
should not matter; patch is attached). I now can't reproduce hangs
with simple stress testing, but running kernel make alongside that
makes it hang sometimes. Example of non-frozen gcc:

gcc D EEE06A70 0 1750 1749 1751
(NOTLB)
df85df38 00000046 bf878130 eee06a70 00004111 eee06a70 eee06a70
003d0900
00000000 c0137cf5 df85c000 00000000 c058ada2 c012503e ef2c915c
ef2c9030
c1c0b480 7c3b8500 003d0927 df85c000 00000a98 7c3b8500 003d0927
c0770800
Call Trace:
[<c0137cf5>] attach_pid+0x25/0xb0
[<c058ada2>] _write_unlock_irq+0x12/0x30
[<c012503e>] copy_process+0xe5e/0x11b0
[<c0588f74>] wait_for_completion+0x94/0xd0
[<c0121690>] default_wake_function+0x0/0x10
[<c01254d9>] do_fork+0x149/0x210
[<c0101218>] sys_vfork+0x28/0x30
[<c0103231>] syscall_call+0x7/0xb

...maybe solving this would solve journalling problems, too? It is
similar AFAICT.
Pavel

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index e24446f..90d6c1a 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -87,7 +87,6 @@ static int prepare_processes(void)
int error;

pm_prepare_console();
- sys_sync();
disable_nonboot_cpus();

if (freeze_processes()) {
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 02a1b3a..bd16e44 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -16,7 +16,7 @@
/*
* Timeout for stopping processes
*/
-#define TIMEOUT (6 * HZ)
+#define TIMEOUT (60 * HZ)

static inline int freezeable(struct task_struct * p)
@@ -54,32 +54,53 @@ void refrigerator(void)
current->state = save;
}

+static void freeze_process(struct task_struct *p)
+{
+ unsigned long flags;
+
+ freeze(p);
+ spin_lock_irqsave(&p->sighand->siglock, flags);
+ signal_wake_up(p, 0);
+ spin_unlock_irqrestore(&p->sighand->siglock, flags);
+}
+
/* 0 = success, else # of processes that we failed to stop */
int freeze_processes(void)
{
- int todo;
+ int todo, user_frozen, nr_user;
unsigned long start_time;
struct task_struct *g, *p;
unsigned long flags;

printk( "Stopping tasks: " );
start_time = jiffies;
+ user_frozen = 0;
do {
- todo = 0;
+ nr_user = todo = 0;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
if (!freezeable(p))
continue;
if (frozen(p))
continue;
-
- freeze(p);
- spin_lock_irqsave(&p->sighand->siglock, flags);
- signal_wake_up(p, 0);
- spin_unlock_irqrestore(&p->sighand->siglock, flags);
- todo++;
+ if (p->mm) {
+ /* The task is a user-space one. Freeze it */
+ freeze_process(p);
+ todo++;
+ nr_user++;
+ } else {
+ /* Freeze only if the user space is frozen */
+ if (user_frozen)
+ freeze_process(p);
+ todo++;
+ }
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
+ if (!user_frozen && !nr_user) {
+ printk("sync");
+ sys_sync();
+ }
+ user_frozen = !nr_user;
yield(); /* Yield is okay here */
if (todo && time_after(jiffies, start_time + TIMEOUT)) {
printk( "\n" );
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 41f6636..c9c293f 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -80,7 +80,7 @@ static int save_highmem_zone(struct zone
void *kaddr;
unsigned long pfn = zone_pfn + zone->zone_start_pfn;

- if (!(pfn%1000))
+ if (!(pfn%10000))
printk(".");
if (!pfn_valid(pfn))
continue;
@@ -121,13 +121,14 @@ int save_highmem(void)
struct zone *zone;
int res = 0;

- pr_debug("swsusp: Saving Highmem\n");
+ pr_debug("swsusp: Saving Highmem");
for_each_zone (zone) {
if (is_highmem(zone))
res = save_highmem_zone(zone);
if (res)
return res;
}
+ printk("\n");
return 0;
}

--
Thanks, Sharp!