[PATCH 1/8] Enhance process freezer interface for usage beyond software suspend

From: Gautham R Shenoy
Date: Mon Apr 02 2007 - 01:37:56 EST

This patch provides an interface to extend the use of the process
freezer beyond Suspend.

The tasks can selectively mark themselves to be exempted from specific
freeze events like SUSPEND /KPROBES/CPU_HOTPLUG.

This patch however, *does not* sort non freezable threads into
different categories based on the freeze events. Thus all
tasks which were previously marked PF_NOFREEZE are now
exempted from freezer using
freezer_exempt(FE_ALL);
which means exempt from all kinds of freezes.

Signed-off-by: Gautham R Shenoy <ego@xxxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>

--
arch/i386/kernel/apm.c | 2 -
drivers/block/loop.c | 2 -
drivers/char/apm-emulation.c | 6 ++--
drivers/ieee1394/ieee1394_core.c | 2 -
drivers/md/md.c | 2 -
drivers/mmc/card/queue.c | 3 +-
drivers/mtd/mtd_blkdevs.c | 3 +-
drivers/scsi/libsas/sas_scsi_host.c | 2 -
drivers/scsi/scsi_error.c | 2 -
drivers/usb/storage/usb.c | 2 -
include/linux/freezer.h | 52 ++++++++++++++++++++++++++++++++----
include/linux/sched.h | 15 +++++++++-
init/do_mounts_initrd.c | 2 -
kernel/fork.c | 2 -
kernel/kprobes.c | 4 +-
kernel/power/disk.c | 4 +-
kernel/power/main.c | 6 ++--
kernel/power/process.c | 29 +++++++++++---------
kernel/power/user.c | 8 ++---
kernel/rcutorture.c | 4 +-
kernel/sched.c | 2 -
kernel/softirq.c | 2 -
kernel/softlockup.c | 2 -
kernel/workqueue.c | 2 -
24 files changed, 110 insertions(+), 50 deletions(-)

Index: linux-2.6.21-rc5/include/linux/sched.h
===================================================================
--- linux-2.6.21-rc5.orig/include/linux/sched.h
+++ linux-2.6.21-rc5/include/linux/sched.h
@@ -1186,8 +1186,21 @@ static inline void put_task_struct(struc
#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_NOFREEZE 0x00008000 /* this thread should not be frozen */
+
+/* Per process freezer specific flags */
+#define PF_FE_SUSPEND 0x00008000 /* This thread should not be frozen
+ * for suspend
+ */
+
+#define PF_FE_KPROBES 0x00000010 /* This thread should not be frozen
+ * for Kprobes
+ */
+
#define PF_FROZEN 0x00010000 /* frozen for system suspend */
+
+#define PF_FE_ALL (PF_FE_SUSPEND | PF_FE_KPROBES)
+ /* Exempt from all kinds freeze chills*/
+
#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
#define PF_KSWAPD 0x00040000 /* I am kswapd */
#define PF_SWAPOFF 0x00080000 /* I am in swapoff */
Index: linux-2.6.21-rc5/include/linux/freezer.h
===================================================================
--- linux-2.6.21-rc5.orig/include/linux/freezer.h
+++ linux-2.6.21-rc5/include/linux/freezer.h
@@ -2,7 +2,49 @@

#include <linux/sched.h>

-#ifdef CONFIG_PM
+#if defined(CONFIG_PM) || defined(CONFIG_HOTPLUG_CPU) || \
+ defined(CONFIG_KPROBES)
+
+/* These are the events which make use of the process freezer */
+#define FE_NONE 0
+#define FE_ALL PF_FE_ALL
+#define FE_SUSPEND PF_FE_SUSPEND
+#define FE_KPROBES PF_FE_KPROBES
+
+/*
+ * Exempt the current process from being frozen for a certain event
+ */
+static inline void freezer_exempt(unsigned long exempt_freeze_event)
+{
+ if (exempt_freeze_event == FE_NONE)
+ current->flags &= ~PF_FE_ALL;
+ else
+ current->flags |= exempt_freeze_event;
+}
+
+/*
+ * Consider the current process to be frozen for a certain event
+ */
+static inline void freezer_consider(unsigned long freeze_event)
+{
+ current->flags &= ~freeze_event;
+}
+
+/*
+ * Check if the process is exempted from freeze for the particular event.
+ */
+static inline int freezer_is_exempted(struct task_struct *p,
+ unsigned long freeze_event)
+{
+ return p->flags & freeze_event;
+}
+
+/* Returns the mask of the events for which this process is freezeable */
+static inline unsigned long freezeable_event_mask(struct task_struct *p)
+{
+ return ~p->flags & PF_FE_ALL;
+}
+
/*
* Check if a process has been frozen
*/
@@ -63,8 +105,8 @@ static inline void frozen_process(struct
}

extern void refrigerator(void);
-extern int freeze_processes(void);
-extern void thaw_processes(void);
+extern int freeze_processes(unsigned long freeze_event);
+extern void thaw_processes(unsigned long freeze_event);

static inline int try_to_freeze(void)
{
@@ -127,8 +169,8 @@ static inline int thaw_process(struct ta
static inline void frozen_process(struct task_struct *p) { BUG(); }

static inline void refrigerator(void) {}
-static inline int freeze_processes(void) { BUG(); return 0; }
-static inline void thaw_processes(void) {}
+static inline int freeze_processes(int a) { BUG(); return 1; }
+static inline void thaw_processes(int a) {}

static inline int try_to_freeze(void) { return 0; }

Index: linux-2.6.21-rc5/kernel/power/process.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/power/process.c
+++ linux-2.6.21-rc5/kernel/power/process.c
@@ -24,10 +24,10 @@
#define FREEZER_KERNEL_THREADS 0
#define FREEZER_USER_SPACE 1

-static inline int freezeable(struct task_struct * p)
+static inline int freezeable(struct task_struct * p, unsigned long freeze_event)
{
if ((p == current) ||
- (p->flags & PF_NOFREEZE) ||
+ (freezer_is_exempted(p, freeze_event)) ||
(p->exit_state != 0))
return 0;
return 1;
@@ -106,7 +106,8 @@ static inline int is_user_space(struct t
return ret;
}

-static unsigned int try_to_freeze_tasks(int freeze_user_space)
+static unsigned int try_to_freeze_tasks(int freeze_user_space,
+ unsigned long freeze_event)
{
struct task_struct *g, *p;
unsigned long end_time;
@@ -117,7 +118,7 @@ static unsigned int try_to_freeze_tasks(
todo = 0;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
- if (!freezeable(p))
+ if (!freezeable(p, freeze_event))
continue;

if (frozen(p))
@@ -158,7 +159,7 @@ static unsigned int try_to_freeze_tasks(
continue;

task_lock(p);
- if (freezeable(p) && !frozen(p) &&
+ if (freezeable(p, freeze_event) && !frozen(p) &&
!freezer_should_skip(p))
printk(KERN_ERR " %s\n", p->comm);

@@ -173,21 +174,23 @@ static unsigned int try_to_freeze_tasks(

/**
* freeze_processes - tell processes to enter the refrigerator
+ * @freeze_event: The system event for which processes are being
+ * frozen.
*
* Returns 0 on success, or the number of processes that didn't freeze,
* although they were told to.
*/
-int freeze_processes(void)
+int freeze_processes(unsigned long freeze_event)
{
unsigned int nr_unfrozen;

printk("Stopping tasks ... ");
- nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
+ nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE, freeze_event);
if (nr_unfrozen)
return nr_unfrozen;

sys_sync();
- nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
+ nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS, freeze_event);
if (nr_unfrozen)
return nr_unfrozen;

@@ -196,13 +199,13 @@ int freeze_processes(void)
return 0;
}

-static void thaw_tasks(int thaw_user_space)
+static void thaw_tasks(int thaw_user_space, unsigned long freeze_event)
{
struct task_struct *g, *p;

read_lock(&tasklist_lock);
do_each_thread(g, p) {
- if (!freezeable(p))
+ if (!freezeable(p, freeze_event))
continue;

if (is_user_space(p) == !thaw_user_space)
@@ -213,11 +216,11 @@ static void thaw_tasks(int thaw_user_spa
read_unlock(&tasklist_lock);
}

-void thaw_processes(void)
+void thaw_processes(unsigned long freeze_event)
{
printk("Restarting tasks ... ");
- thaw_tasks(FREEZER_KERNEL_THREADS);
- thaw_tasks(FREEZER_USER_SPACE);
+ thaw_tasks(FREEZER_KERNEL_THREADS, freeze_event);
+ thaw_tasks(FREEZER_USER_SPACE, freeze_event);
schedule();
printk("done.\n");
}
Index: linux-2.6.21-rc5/kernel/sched.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/sched.c
+++ linux-2.6.21-rc5/kernel/sched.c
@@ -5057,6 +5057,7 @@ static int migration_thread(void *data)
BUG_ON(rq->migration_thread != current);

set_current_state(TASK_INTERRUPTIBLE);
+ freezer_exempt(FE_ALL);
while (!kthread_should_stop()) {
struct migration_req *req;
struct list_head *head;
@@ -5407,7 +5408,6 @@ migration_call(struct notifier_block *nf
p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
if (IS_ERR(p))
return NOTIFY_BAD;
- p->flags |= PF_NOFREEZE;
kthread_bind(p, cpu);
/* Must be high prio: stop_machine expects to yield to it. */
rq = task_rq_lock(p, &flags);
Index: linux-2.6.21-rc5/kernel/softlockup.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/softlockup.c
+++ linux-2.6.21-rc5/kernel/softlockup.c
@@ -96,7 +96,7 @@ static int watchdog(void * __bind_cpu)
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };

sched_setscheduler(current, SCHED_FIFO, &param);
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

/*
* Run briefly once per second to reset the softlockup timestamp.
Index: linux-2.6.21-rc5/kernel/workqueue.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/workqueue.c
+++ linux-2.6.21-rc5/kernel/workqueue.c
@@ -292,7 +292,7 @@ static int worker_thread(void *__cwq)
struct k_sigaction sa;

if (!cwq->wq->freezeable)
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

/*
* We inherited MPOL_INTERLEAVE from the booting kernel.
Index: linux-2.6.21-rc5/kernel/rcutorture.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/rcutorture.c
+++ linux-2.6.21-rc5/kernel/rcutorture.c
@@ -559,7 +559,7 @@ rcu_torture_fakewriter(void *arg)

VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
set_user_nice(current, 19);
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

do {
schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
@@ -590,7 +590,7 @@ rcu_torture_reader(void *arg)

VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
set_user_nice(current, 19);
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

do {
idx = cur_ops->readlock();
Index: linux-2.6.21-rc5/arch/i386/kernel/apm.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/i386/kernel/apm.c
+++ linux-2.6.21-rc5/arch/i386/kernel/apm.c
@@ -1395,6 +1395,7 @@ static void apm_mainloop(void)

add_wait_queue(&apm_waitqueue, &wait);
set_current_state(TASK_INTERRUPTIBLE);
+ freezer_exempt(FE_ALL);
for (;;) {
try_to_freeze();
schedule_timeout(APM_CHECK_TIMEOUT);
@@ -2315,7 +2316,6 @@ static int __init apm_init(void)
remove_proc_entry("apm", NULL);
return err;
}
- kapmd_task->flags |= PF_NOFREEZE;
wake_up_process(kapmd_task);

if (num_online_cpus() > 1 && !smp ) {
Index: linux-2.6.21-rc5/drivers/char/apm-emulation.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/char/apm-emulation.c
+++ linux-2.6.21-rc5/drivers/char/apm-emulation.c
@@ -336,7 +336,7 @@ apm_ioctl(struct inode * inode, struct f
* threads.
*/
flags = current->flags;
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

wait_event(apm_suspend_waitqueue,
as->suspend_state == SUSPEND_DONE);
@@ -372,7 +372,7 @@ apm_ioctl(struct inode * inode, struct f
* threads.
*/
flags = current->flags;
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

wait_event_interruptible(apm_suspend_waitqueue,
as->suspend_state == SUSPEND_DONE);
@@ -536,6 +536,7 @@ static int apm_get_info(char *buf, char

static int kapmd(void *arg)
{
+ freezer_exempt(FE_ALL);
do {
apm_event_t event;
int ret;
@@ -601,7 +602,6 @@ static int __init apm_init(void)
kapmd_tsk = NULL;
return ret;
}
- kapmd_tsk->flags |= PF_NOFREEZE;
wake_up_process(kapmd_tsk);

#ifdef CONFIG_PROC_FS
Index: linux-2.6.21-rc5/drivers/block/loop.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/block/loop.c
+++ linux-2.6.21-rc5/drivers/block/loop.c
@@ -587,7 +587,7 @@ static int loop_thread(void *data)
* hence, it mustn't be stopped at all
* because it could be indirectly used during suspension
*/
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

set_user_nice(current, -20);

Index: linux-2.6.21-rc5/drivers/ieee1394/ieee1394_core.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/ieee1394/ieee1394_core.c
+++ linux-2.6.21-rc5/drivers/ieee1394/ieee1394_core.c
@@ -1134,7 +1134,7 @@ static int hpsbpkt_thread(void *__hi)
struct list_head tmp;
int may_schedule;

- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

while (!kthread_should_stop()) {

Index: linux-2.6.21-rc5/drivers/md/md.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/md/md.c
+++ linux-2.6.21-rc5/drivers/md/md.c
@@ -4527,7 +4527,7 @@ static int md_thread(void * arg)
* many dirty RAID5 blocks.
*/

- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);
allow_signal(SIGKILL);
while (!kthread_should_stop()) {

Index: linux-2.6.21-rc5/drivers/mtd/mtd_blkdevs.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/mtd/mtd_blkdevs.c
+++ linux-2.6.21-rc5/drivers/mtd/mtd_blkdevs.c
@@ -82,7 +82,8 @@ static int mtd_blktrans_thread(void *arg
struct request_queue *rq = tr->blkcore_priv->rq;

/* we might get involved when memory gets low, so use PF_MEMALLOC */
- current->flags |= PF_MEMALLOC | PF_NOFREEZE;
+ current->flags |= PF_MEMALLOC;
+ freezer_exempt(FE_ALL);

daemonize("%sd", tr->name);

Index: linux-2.6.21-rc5/drivers/scsi/libsas/sas_scsi_host.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/scsi/libsas/sas_scsi_host.c
+++ linux-2.6.21-rc5/drivers/scsi/libsas/sas_scsi_host.c
@@ -871,7 +871,7 @@ static int sas_queue_thread(void *_sas_h
struct scsi_core *core = &sas_ha->core;

daemonize("sas_queue_%d", core->shost->host_no);
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

complete(&queue_th_comp);

Index: linux-2.6.21-rc5/drivers/scsi/scsi_error.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/scsi/scsi_error.c
+++ linux-2.6.21-rc5/drivers/scsi/scsi_error.c
@@ -1536,7 +1536,7 @@ int scsi_error_handler(void *data)
{
struct Scsi_Host *shost = data;

- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

/*
* We use TASK_INTERRUPTIBLE so that the thread is not
Index: linux-2.6.21-rc5/drivers/usb/storage/usb.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/usb/storage/usb.c
+++ linux-2.6.21-rc5/drivers/usb/storage/usb.c
@@ -301,7 +301,7 @@ static int usb_stor_control_thread(void
struct us_data *us = (struct us_data *)__us;
struct Scsi_Host *host = us_to_host(us);

- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

for(;;) {
try_to_freeze();
Index: linux-2.6.21-rc5/init/do_mounts_initrd.c
===================================================================
--- linux-2.6.21-rc5.orig/init/do_mounts_initrd.c
+++ linux-2.6.21-rc5/init/do_mounts_initrd.c
@@ -55,7 +55,7 @@ static void __init handle_initrd(void)
sys_mount(".", "/", NULL, MS_MOVE, NULL);
sys_chroot(".");

- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);
pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD);
if (pid > 0) {
while (pid != sys_wait4(-1, NULL, 0, NULL))
Index: linux-2.6.21-rc5/kernel/softirq.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/softirq.c
+++ linux-2.6.21-rc5/kernel/softirq.c
@@ -490,7 +490,7 @@ void __init softirq_init(void)
static int ksoftirqd(void * __bind_cpu)
{
set_user_nice(current, 19);
- current->flags |= PF_NOFREEZE;
+ freezer_exempt(FE_ALL);

set_current_state(TASK_INTERRUPTIBLE);

Index: linux-2.6.21-rc5/kernel/kprobes.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/kprobes.c
+++ linux-2.6.21-rc5/kernel/kprobes.c
@@ -104,7 +104,7 @@ static int __kprobes check_safety(void)
{
int ret = 0;
#if defined(CONFIG_PREEMPT) && defined(CONFIG_PM)
- ret = freeze_processes();
+ ret = freeze_processes(FE_KPROBES);
if (ret == 0) {
struct task_struct *p, *q;
do_each_thread(p, q) {
@@ -117,7 +117,7 @@ static int __kprobes check_safety(void)
} while_each_thread(p, q);
}
loop_end:
- thaw_processes();
+ thaw_processes(FE_KPROBES);
#else
synchronize_sched();
#endif
Index: linux-2.6.21-rc5/kernel/power/disk.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/power/disk.c
+++ linux-2.6.21-rc5/kernel/power/disk.c
@@ -104,7 +104,7 @@ static inline void platform_finish(void)

static void unprepare_processes(void)
{
- thaw_processes();
+ thaw_processes(FE_SUSPEND);
pm_restore_console();
}

@@ -113,7 +113,7 @@ static int prepare_processes(void)
int error = 0;

pm_prepare_console();
- if (freeze_processes()) {
+ if (freeze_processes(FE_SUSPEND)) {
error = -EBUSY;
unprepare_processes();
}
Index: linux-2.6.21-rc5/kernel/power/main.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/power/main.c
+++ linux-2.6.21-rc5/kernel/power/main.c
@@ -86,7 +86,7 @@ static int suspend_prepare(suspend_state

pm_prepare_console();

- if (freeze_processes()) {
+ if (freeze_processes(FE_SUSPEND)) {
error = -EAGAIN;
goto Thaw;
}
@@ -123,7 +123,7 @@ static int suspend_prepare(suspend_state
device_resume();
resume_console();
Thaw:
- thaw_processes();
+ thaw_processes(FE_SUSPEND);
pm_restore_console();
return error;
}
@@ -162,7 +162,7 @@ static void suspend_finish(suspend_state
pm_finish(state);
device_resume();
resume_console();
- thaw_processes();
+ thaw_processes(FE_SUSPEND);
pm_restore_console();
}

Index: linux-2.6.21-rc5/kernel/power/user.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/power/user.c
+++ linux-2.6.21-rc5/kernel/power/user.c
@@ -88,7 +88,7 @@ static int snapshot_release(struct inode
free_bitmap(data->bitmap);
if (data->frozen) {
mutex_lock(&pm_mutex);
- thaw_processes();
+ thaw_processes(FE_SUSPEND);
enable_nonboot_cpus();
mutex_unlock(&pm_mutex);
}
@@ -239,8 +239,8 @@ static int snapshot_ioctl(struct inode *
if (data->frozen)
break;
mutex_lock(&pm_mutex);
- if (freeze_processes()) {
- thaw_processes();
+ if (freeze_processes(FE_SUSPEND)) {
+ thaw_processes(FE_SUSPEND);
error = -EBUSY;
}
mutex_unlock(&pm_mutex);
@@ -252,7 +252,7 @@ static int snapshot_ioctl(struct inode *
if (!data->frozen)
break;
mutex_lock(&pm_mutex);
- thaw_processes();
+ thaw_processes(FE_SUSPEND);
mutex_unlock(&pm_mutex);
data->frozen = 0;
break;
Index: linux-2.6.21-rc5/drivers/mmc/card/queue.c
===================================================================
--- linux-2.6.21-rc5.orig/drivers/mmc/card/queue.c
+++ linux-2.6.21-rc5/drivers/mmc/card/queue.c
@@ -66,7 +66,8 @@ static int mmc_queue_thread(void *d)
* Set iothread to ensure that we aren't put to sleep by
* the process freezing. We handle suspension ourselves.
*/
- current->flags |= PF_MEMALLOC|PF_NOFREEZE;
+ current->flags |= PF_MEMALLOC;
+ freezer_exempt(FE_ALL);

down(&mq->thread_sem);
do {
Index: linux-2.6.21-rc5/kernel/fork.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/fork.c
+++ linux-2.6.21-rc5/kernel/fork.c
@@ -921,7 +921,7 @@ static inline void copy_flags(unsigned l
{
unsigned long new_flags = p->flags;

- new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
+ new_flags &= ~(PF_SUPERPRIV | PF_FE_ALL);
new_flags |= PF_FORKNOEXEC;
new_flags |= PF_STARTING;
p->flags = new_flags;
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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