On Mon, 5 Nov 2007, Rafael J. Wysocki wrote:
> I like the idea, but I think that start_icebox() should be called after
> freeze_processes(). Similarly, IMO it's better to call stop_icebox() before
> thaw_processes().
Okay. On the assumption that freezable kernel threads will continue to
use the freezer and won't try to use the icebox, I have updated the
patch. Other comments?
Alan Stern
P.S.: What about mutual exclusion in kernel/power/user.c? If we stop
freezing user tasks, there's nothing to prevent more than one task
holding an open file reference to the snapshot file and submitting
ioctls concurrently. Maybe the regions covered by pm_mutex should be
expanded.
Index: usb-2.6/include/linux/freezer.h
===================================================================
--- usb-2.6.orig/include/linux/freezer.h
+++ usb-2.6/include/linux/freezer.h
@@ -157,6 +157,12 @@ static inline void set_freezable(void)
} while (try_to_freeze()); \
__retval; \
})
+
+/*
+ * Kernel threads that want to freeze themselves go into the icebox.
+ */
+extern void icebox(void);
+
#else /* !CONFIG_PM_SLEEP */
static inline int frozen(struct task_struct *p) { return 0; }
static inline int freezing(struct task_struct *p) { return 0; }
@@ -181,6 +187,7 @@ static inline void set_freezable(void) {
#define wait_event_freezable_timeout(wq, condition, timeout) \
wait_event_interruptible_timeout(wq, condition, timeout)
+static inline void icebox(void) {}
#endif /* !CONFIG_PM_SLEEP */
#endif /* FREEZER_H_INCLUDED */
Index: usb-2.6/kernel/power/power.h
===================================================================
--- usb-2.6.orig/kernel/power/power.h
+++ usb-2.6/kernel/power/power.h
@@ -207,3 +207,9 @@ static inline int suspend_devices_and_en
/* kernel/power/main.c */
extern int pm_notifier_call_chain(unsigned long val);
#endif
+
+#ifdef CONFIG_PM_SLEEP
+/* kerne/power/process.c */
+extern void start_icebox(void);
+extern void stop_icebox(void);
+#endif
Index: usb-2.6/kernel/power/main.c
===================================================================
--- usb-2.6.orig/kernel/power/main.c
+++ usb-2.6/kernel/power/main.c
@@ -108,6 +108,8 @@ static int suspend_prepare(void)
goto Thaw;
}
+ start_icebox();
+
free_pages = global_page_state(NR_FREE_PAGES);
if (free_pages < FREE_PAGE_NUMBER) {
pr_debug("PM: free some memory\n");
@@ -120,6 +122,7 @@ static int suspend_prepare(void)
if (!error)
return 0;
+ stop_icebox();
Thaw:
thaw_processes();
pm_restore_console();
@@ -215,6 +218,7 @@ int suspend_devices_and_enter(suspend_st
*/
static void suspend_finish(void)
{
+ stop_icebox();
thaw_processes();
pm_restore_console();
pm_notifier_call_chain(PM_POST_SUSPEND);
Index: usb-2.6/kernel/power/disk.c
===================================================================
--- usb-2.6.orig/kernel/power/disk.c
+++ usb-2.6/kernel/power/disk.c
@@ -406,6 +406,8 @@ int hibernate(void)
if (error)
goto Finish;
+ start_icebox();
+
if (hibernation_mode == HIBERNATION_TESTPROC) {
printk("swsusp debug: Waiting for 5 seconds.\n");
mdelay(5000);
@@ -427,6 +429,7 @@ int hibernate(void)
swsusp_free();
}
Thaw:
+ stop_icebox();
unprepare_processes();
Finish:
free_basic_memory_bitmaps();
@@ -504,6 +507,8 @@ static int software_resume(void)
goto Done;
}
+ start_icebox();
+
pr_debug("PM: Reading swsusp image.\n");
error = swsusp_read(&flags);
@@ -512,6 +517,7 @@ static int software_resume(void)
printk(KERN_ERR "PM: Restore failed, recovering.\n");
swsusp_free();
+ stop_icebox();
unprepare_processes();
Done:
free_basic_memory_bitmaps();
Index: usb-2.6/kernel/power/user.c
===================================================================
--- usb-2.6.orig/kernel/power/user.c
+++ usb-2.6/kernel/power/user.c
@@ -172,13 +172,16 @@ static int snapshot_ioctl(struct inode *
if (error)
thaw_processes();
mutex_unlock(&pm_mutex);
- if (!error)
+ if (!error) {
data->frozen = 1;
+ start_icebox();
+ }
break;
case SNAPSHOT_UNFREEZE:
if (!data->frozen || data->ready)
break;
+ stop_icebox();
mutex_lock(&pm_mutex);
thaw_processes();
mutex_unlock(&pm_mutex);
Index: usb-2.6/kernel/power/process.c
===================================================================
--- usb-2.6.orig/kernel/power/process.c
+++ usb-2.6/kernel/power/process.c
@@ -14,6 +14,8 @@
#include <linux/syscalls.h>
#include <linux/freezer.h>
+#include "power.h"
+
/*
* Timeout for stopping processes
*/
@@ -283,3 +285,52 @@ void thaw_processes(void)
}
EXPORT_SYMBOL(refrigerator);
+
+/*
+ * Routines for kernel threads that want to freeze themselves in the icebox
+ */
+static DECLARE_WAIT_QUEUE_HEAD(icebox_wait_queue_head);
+static int icebox_active;
+
+/**
+ * start_icebox -- activate the icebox
+ *
+ * Kernel power code should call this routine before sending the
+ * PM_HIBERNATION_PREPARE, PM_SUSPEND_PREPARE, or PM_RESTORE_PREPARE
+ * notifications.
+ */
+void start_icebox(void)
+{
+ icebox_active = 1;
+}
+
+/**
+ * stop_icebox -- deactivate the icebox and awaken waiting threads
+ *
+ * Kernel power code should call this routine before sending the
+ * PM_POST_HIBERNATION, PM_POST_SUSPEND, or PM_POST_RESTORE notifications.
+ */
+void stop_icebox(void)
+{
+ icebox_active = 0;
+ wake_up_all(&icebox_wait_queue_head);
+}
+
+/**
+ * icebox -- place for kernel threads to wait during suspend or hibernation
+ *
+ * Tasks can call this routine at any time. It will return immediately
+ * unless a system suspend or hibernation has started and the icebox is
+ * active, in which case it won't return until the suspend/hibernation
+ * is over.
+ *
+ * This routine should be used by drivers that want to delay user-initiated
+ * I/O until a system sleep is over. Kernel threads should not use it
+ * in place of the freezer, because the icebox doesn't get activated until
+ * after freezing is complete.
+ */
+void icebox(void)
+{
+ wait_event(icebox_wait_queue_head, !icebox_active);
+}
+EXPORT_SYMBOL_GPL(icebox);
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