(Sorry everyone else for emailing you too. I'm only doing so to honour
the convention of not removing people from replies.)
Hi Christoph.
As I look at the patch in preparation for sending it, I don't think I
really changed anything significant. (I didn't address the issues I
mentioned in the previous email).
The only thing I think might be worth mentioning is that I added
freeze_processes and thaw_processes declarations to
include/linux/suspend.h. I got warnings without them there - perhaps,
though, it's just due to differences in Suspend2.
Having said this, I promised to send you my version, so I've inlined it
below. As you'll see, I'm making some changes just to minimise the
differences with swsusp.
Regards,
Nigel
Documentation/power/kernel_threads.txt | 10 +-
Documentation/power/swsusp.txt | 5 -
include/linux/sched.h | 1
kernel/power/process.c | 114 ++++++++++++++++++---------------
4 files changed, 72 insertions(+), 58 deletions(-)
diff -ruNp 992-suspend_fix.patch-old/Documentation/power/kernel_threads.txt 992-suspend_fix.patch-new/Documentation/power/kernel_threads.txt
--- 992-suspend_fix.patch-old/Documentation/power/kernel_threads.txt 2005-08-08 17:23:31.000000000 +1000
+++ 992-suspend_fix.patch-new/Documentation/power/kernel_threads.txt 2005-08-09 08:11:41.000000000 +1000
@@ -4,15 +4,15 @@ KERNEL THREADS
Freezer
Upon entering a suspended state the system will freeze all
-tasks. This is done by delivering pseudosignals. This affects
-kernel threads, too. To successfully freeze a kernel thread
-the thread has to check for the pseudosignal and enter the
-refrigerator. Code to do this looks like this:
+tasks. This is done by making all processes execute a notifier.
+This affects kernel threads, too. To successfully freeze a kernel thread
+the thread has to check for the notifications and call the notifier
+chain for the process. Code to do this looks like this:
do {
hub_events();
wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list));
- try_to_freeze();
+ try_todo_list();
} while (!signal_pending(current));
from drivers/usb/core/hub.c::hub_thread()
diff -ruNp 992-suspend_fix.patch-old/Documentation/power/swsusp.txt 992-suspend_fix.patch-new/Documentation/power/swsusp.txt
--- 992-suspend_fix.patch-old/Documentation/power/swsusp.txt 2005-08-08 17:23:31.000000000 +1000
+++ 992-suspend_fix.patch-new/Documentation/power/swsusp.txt 2005-08-09 08:11:41.000000000 +1000
@@ -155,7 +155,8 @@ should be sent to the mailing list avail
website, and not to the Linux Kernel Mailing List. We are working
toward merging suspend2 into the mainline kernel.
-Q: A kernel thread must voluntarily freeze itself (call 'refrigerator').
+Q: A kernel thread must work on the todo list (call 'run_todo_list')
+to enter the refrigerator.
I found some kernel threads that don't do it, and they don't freeze
so the system can't sleep. Is this a known behavior?
@@ -164,7 +165,7 @@ place where the thread is safe to be fro
should be held at that point and it must be safe to sleep there), and
add:
- try_to_freeze();
+ try_todo_list();
If the thread is needed for writing the image to storage, you should
instead set the PF_NOFREEZE process flag when creating the thread (and
diff -ruNp 992-suspend_fix.patch-old/include/linux/sched.h 992-suspend_fix.patch-new/include/linux/sched.h
--- 992-suspend_fix.patch-old/include/linux/sched.h 2005-08-09 11:17:49.000000000 +1000
+++ 992-suspend_fix.patch-new/include/linux/sched.h 2005-08-09 08:11:41.000000000 +1000
@@ -835,7 +835,6 @@ do { if (atomic_dec_and_test(&(tsk)->usa
#define PF_MEMALLOC 0x00000800 /* Allocating memory */
#define PF_FLUSHER 0x00001000 /* responsible for disk writeback */
#define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
-#define PF_FREEZE 0x00004000 /* this task is being frozen for suspend now */
#define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
#define PF_FROZEN 0x00010000 /* frozen for system suspend */
#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
diff -ruNp 992-suspend_fix.patch-old/kernel/power/process.c 992-suspend_fix.patch-new/kernel/power/process.c
--- 992-suspend_fix.patch-old/kernel/power/process.c 2005-08-09 11:17:48.000000000 +1000
+++ 992-suspend_fix.patch-new/kernel/power/process.c 2005-08-09 11:10:59.000000000 +1000
@@ -61,6 +61,11 @@ extern void suspend_relinquish_console(v
static void freeze_lru(void);
extern void thaw_lru(void);
+DECLARE_COMPLETION(kernelspace_thaw);
+DECLARE_COMPLETION(userspace_thaw);
+static atomic_t nr_userspace_frozen;
+static atomic_t nr_kernelspace_frozen;
+
/*
* to_be_frozen
*
@@ -72,7 +77,7 @@ extern void thaw_lru(void);
static int to_be_frozen(struct task_struct * p, int type_being_frozen) {
if ((p == current) ||
- (frozen(p)) ||
+ (p->flags & PF_FROZEN) ||
(p->flags & PF_NOFREEZE) ||
(p->exit_state == EXIT_ZOMBIE) ||
(p->exit_state == EXIT_DEAD) ||
@@ -86,47 +91,68 @@ static int to_be_frozen(struct task_stru
return 1;
}
-/**
- * refrigerator - idle routine for frozen processes
- * @flag: unsigned long, non zero if signals to be flushed.
- *
- * A routine for kernel threads which should not do work during suspend
- * to enter and spin in until the process is finished.
+/*
+ * Invoked by the task todo list notifier when the task to be
+ * frozen is running.
*/
-
-void refrigerator(void)
+static int freeze_process(struct notifier_block *nl, unsigned long x, void *v)
{
- unsigned long flags;
+ /* Hmm, should we be allowed to suspend when there are realtime
+ processes around? */
long save;
+
+ save = current->state;
+ current->flags |= PF_FROZEN;
+ notifier_chain_unregister(¤t->todo, nl);
+ kfree(nl);
- spin_lock_irqsave(¤t->sighand->siglock, flags);
+ spin_lock_irq(¤t->sighand->siglock);
recalc_sigpending();
- spin_unlock_irqrestore(¤t->sighand->siglock, flags);
+ spin_unlock_irq(¤t->sighand->siglock);
- if (unlikely(current->flags & PF_NOFREEZE)) {
- current->flags &= ~PF_FREEZE;
- return;
+ if (current->mm) {
+ atomic_inc(&nr_userspace_frozen);
+ wait_for_completion(&userspace_thaw);
+ atomic_dec(&nr_userspace_frozen);
+ } else {
+ atomic_inc(&nr_kernelspace_frozen);
+ wait_for_completion(&kernelspace_thaw);
+ atomic_dec(&nr_kernelspace_frozen);
}
- save = current->state;
- suspend_message(SUSPEND_FREEZER, SUSPEND_VERBOSE, 0,
- "\n%s (%d) refrigerated and sigpending recalculated.",
- current->comm, current->pid);
+ current->flags &= ~PF_FROZEN;
+ current->state = save;
- frozen_process(current);
+ return 0;
+}
- while (test_suspend_state(SUSPEND_FREEZER_ON) && frozen(current)) {
- current->state = TASK_STOPPED;
- schedule();
- spin_lock_irqsave(¤t->sighand->siglock, flags);
- recalc_sigpending();
- spin_unlock_irqrestore(¤t->sighand->siglock, flags);
- }
+static inline void freeze(struct task_struct *p)
+{
+ unsigned long flags;
+
+ /*
+ * We only freeze if the todo list is empty to avoid
+ * putting multiple freeze handlers on the todo list.
+ */
- current->state = save;
-}
+ if (!p->todo) {
+ struct notifier_block *n;
+ n = kmalloc(sizeof(struct notifier_block),
+ GFP_ATOMIC);
+ if (n) {
+ n->notifier_call = freeze_process;
+ n->priority = 0;
+ notifier_chain_register(&p->todo, n);
+ }
+ }
+ /* Make the process work on its todo list */
+ spin_lock_irqsave(&p->sighand->siglock, flags);
+ recalc_sigpending();
+ signal_wake_up(p, 0);
+ spin_unlock_irqrestore(&p->sighand->siglock, flags);
+}
/*
* num_to_be_frozen
@@ -204,6 +230,12 @@ static int freeze_threads(int type, int
unsigned long start_time = jiffies;
int result = 0, still_to_do;
+ if (!atomic_read(&nr_userspace_frozen))
+ init_completion(&userspace_thaw);
+
+ if (!atomic_read(&nr_kernelspace_frozen))
+ init_completion(&kernelspace_thaw);
+
suspend_message(SUSPEND_FREEZER, SUSPEND_VERBOSE, 1,
"\n STARTING TO FREEZE TYPE %d THREADS.\n",
type);
@@ -388,7 +420,6 @@ aborting:
void thaw_processes(int which_threads)
{
- struct task_struct *p, *g;
suspend_message(SUSPEND_FREEZER, SUSPEND_LOW, 1, "Thawing tasks\n");
suspend_task = 0;
@@ -397,27 +428,10 @@ void thaw_processes(int which_threads)
clear_suspend_state(SUSPEND_DISABLE_SYNCING);
- preempt_disable();
-
- local_irq_disable();
+ complete_all(&kernelspace_thaw);
- read_lock(&tasklist_lock);
-
- do_each_thread(g, p) {
- if (frozen(p)) {
- if ((which_threads == FREEZER_KERNEL_THREADS) && p->mm)
- continue;
- suspend_message(SUSPEND_FREEZER, SUSPEND_VERBOSE, 0,
- "Waking %5d: %s.\n", p->pid, p->comm);
- thaw_process(p);
- }
- } while_each_thread(g, p);
-
- read_unlock(&tasklist_lock);
-
- preempt_enable();
-
- local_irq_enable();
+ if (which_threads != FREEZER_KERNEL_THREADS)
+ complete_all(&userspace_thaw);
schedule();
}
-
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