Re: Software suspend testing in 2.6.0-test1

Peter Osterlund
2003-07-21T09:47:12Z

Pavel Machek <pavel@ucw.cz> writes:

> > I have done some testing of the software suspend function in
> > 2.6.0-test1. It works mostly very well, but I have found two problems.
> >
> > The first problem is that software suspend fails if a process is
> > stopped before you invoke suspend. (For example, by starting cat from
> > the shell and pressing ctrl-z.) When the processes are woken up again,
> > the cat process is stuck in the schedule loop in refrigerator(),
> > sucking up all available cpu time.
>
> Thanks for a report. If it came with a patch it would be better
> ;-). I'll take a look.

Here is a patch to make software suspend correctly handle stopped
processes. It should apply cleanly on top of the patch you sent to
Linus to decouple SOFTWARE_SUSPEND and ACPI_SLEEP.

diff -u -r orig/linux-stopped/kernel/suspend.c linux-stopped/kernel/suspend.c
--- orig/linux-stopped/kernel/suspend.c Sun Jul 20 11:14:58 2003
+++ linux-stopped/kernel/suspend.c Mon Jul 21 11:51:51 2003
@@ -164,14 +164,18 @@
* Refrigerator and related stuff
*/

-#define INTERESTING(p) \
- /* We don't want to touch kernel_threads..*/ \
- if (p->flags & PF_IOTHREAD) \
- continue; \
- if (p == current) \
- continue; \
- if (p->state == TASK_ZOMBIE) \
- continue;
+/* 0 = Ignore this process when freezing/thawing, 1 = freeze/thaw this process */
+static inline int interesting_process(struct task_struct *p)
+{
+ if (p->flags & PF_IOTHREAD)
+ return 0;
+ if (p == current)
+ return 0;
+ if ((p->state == TASK_ZOMBIE) || (p->state == TASK_DEAD))
+ return 0;
+
+ return 1;
+}

#define TIMEOUT (6 * HZ) /* Timeout for stopping processes */

@@ -214,9 +218,12 @@
read_lock(&tasklist_lock);
do_each_thread(g, p) {
unsigned long flags;
- INTERESTING(p);
+ if (!interesting_process(p))
+ continue;
if (p->flags & PF_FROZEN)
continue;
+ if (p->state == TASK_STOPPED)
+ continue;

/* FIXME: smp problem here: we may not access other process' flags
without locking */
@@ -247,12 +254,15 @@
printk( "Restarting tasks..." );
read_lock(&tasklist_lock);
do_each_thread(g, p) {
- INTERESTING(p);
-
- if (p->flags & PF_FROZEN) p->flags &= ~PF_FROZEN;
- else
- printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
- wake_up_process(p);
+ if (!interesting_process(p))
+ continue;
+
+ p->flags &= ~PF_FREEZE;
+ if (p->flags & PF_FROZEN) {
+ p->flags &= ~PF_FROZEN;
+ wake_up_process(p);
+ } else
+ PRINTK(KERN_INFO " Strange, %s not frozen\n", p->comm );
} while_each_thread(g, p);

read_unlock(&tasklist_lock);

--
Peter Osterlund - petero2@telia.com