From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
This revamps the apm-emulation code to get suspend notifications
regardless of what way pm_suspend() was invoked, whether via the
apm ioctl or via /sys/power/state. Also do some code cleanup and
add comments while at it.
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
drivers/char/apm-emulation.c | 346 +++++++++++++++++++++++++------------------
1 file changed, 207 insertions(+), 139 deletions(-)
Index: linux-2.6/drivers/char/apm-emulation.c
===================================================================
--- linux-2.6.orig/drivers/char/apm-emulation.c
+++ linux-2.6/drivers/char/apm-emulation.c
@@ -58,6 +58,55 @@ struct apm_queue {
};
/*
+ * thread states (for threads using a writable /dev/apm_bios fd):
+ *
+ * SUSPEND_NONE: nothing happening
+ * SUSPEND_PENDING: suspend event queued for thread and pending to be read
+ * SUSPEND_READ: suspend event read, pending acknowledgement
+ * SUSPEND_ACKED: acknowledgement received from thread (via ioctl),
+ * waiting for resume
+ * SUSPEND_ACKTO: acknowledgement timeout
+ * SUSPEND_DONE: thread had acked suspend and is now notified of
+ * resume
+ *
+ * SUSPEND_WAIT: this thread invoked suspend and is waiting for resume
+ *
+ * A thread migrates in one of three paths:
+ * NONE -1-> PENDING -2-> READ -3-> ACKED -4-> DONE -5-> NONE
+ * -6-> ACKTO -7-> NONE
+ * NONE -8-> WAIT -9-> NONE
+ *
+ * While in PENDING or READ, the thread is accounted for in the
+ * suspend_acks_pending counter.
+ *
+ * The transitions are invoked as follows:
+ * 1: suspend event is signalled from the core PM code
+ * 2: the suspend event is read from the fd by the userspace thread
+ * 3: userspace thread issues the APM_IOC_SUSPEND ioctl (as ack)
+ * 4: core PM code signals that we have resumed
+ * 5: APM_IOC_SUSPEND ioctl returns
+ *
+ * 6: the notifier invoked from the core PM code timed out waiting
+ * for all relevant threds to enter ACKED state and puts those
+ * that haven't into ACKTO
+ * 7: those threads issue APM_IOC_SUSPEND ioctl too late,
+ * get an error
+ *
+ * 8: userspace thread issues the APM_IOC_SUSPEND ioctl (to suspend),
+ * ioctl code invokes pm_suspend()
+ * 9: pm_suspend() returns indicating resume
+ */
+enum apm_suspend_state {
+ SUSPEND_NONE,
+ SUSPEND_PENDING,
+ SUSPEND_READ,
+ SUSPEND_ACKED,
+ SUSPEND_ACKTO,
+ SUSPEND_WAIT,
+ SUSPEND_DONE,
+};
+
+/*
* The per-file APM data
*/
struct apm_user {
@@ -68,13 +117,7 @@ struct apm_user {
unsigned int reader: 1;
int suspend_result;
- unsigned int suspend_state;
-#define SUSPEND_NONE 0 /* no suspend pending */
-#define SUSPEND_PENDING 1 /* suspend pending read */
-#define SUSPEND_READ 2 /* suspend read, pending ack */
-#define SUSPEND_ACKED 3 /* suspend acked */
-#define SUSPEND_WAIT 4 /* waiting for suspend */
-#define SUSPEND_DONE 5 /* suspend completed */
+ enum apm_suspend_state suspend_state;
struct apm_queue queue;
};
@@ -82,7 +125,8 @@ struct apm_user {
/*
* Local variables
*/
-static int suspends_pending;
+static atomic_t suspend_acks_pending = ATOMIC_INIT(0);
+static atomic_t userspace_notification_inhibit = ATOMIC_INIT(0);
static int apm_disabled;
static struct task_struct *kapmd_tsk;
@@ -165,78 +209,6 @@ static void queue_event(apm_event_t even
wake_up_interruptible(&apm_waitqueue);
}
-/*
- * queue_suspend_event - queue an APM suspend event.
- *
- * Check that we're in a state where we can suspend. If not,
- * return -EBUSY. Otherwise, queue an event to all "writer"
- * users. If there are no "writer" users, return '1' to
- * indicate that we can immediately suspend.
- */
-static int queue_suspend_event(apm_event_t event, struct apm_user *sender)
-{
- struct apm_user *as;
- int ret = 1;
-
- mutex_lock(&state_lock);
- down_read(&user_list_lock);
-
- /*
- * If a thread is still processing, we can't suspend, so reject
- * the request.
- */
- list_for_each_entry(as, &apm_user_list, list) {
- if (as != sender && as->reader && as->writer && as->suser &&
- as->suspend_state != SUSPEND_NONE) {
- ret = -EBUSY;
- goto out;
- }
- }
-
- list_for_each_entry(as, &apm_user_list, list) {
- if (as != sender && as->reader && as->writer && as->suser) {
- as->suspend_state = SUSPEND_PENDING;
- suspends_pending++;
- queue_add_event(&as->queue, event);
- ret = 0;
- }
- }
- out:
- up_read(&user_list_lock);
- mutex_unlock(&state_lock);
- wake_up_interruptible(&apm_waitqueue);
- return ret;
-}
-
-static void apm_suspend(void)
-{
- struct apm_user *as;
- int err = pm_suspend(PM_SUSPEND_MEM);
-
- /*
- * Anyone on the APM queues will think we're still suspended.
- * Send a message so everyone knows we're now awake again.
- */
- queue_event(APM_NORMAL_RESUME);
-
- /*
- * Finally, wake up anyone who is sleeping on the suspend.
- */
- mutex_lock(&state_lock);
- down_read(&user_list_lock);
- list_for_each_entry(as, &apm_user_list, list) {
- if (as->suspend_state == SUSPEND_WAIT ||
- as->suspend_state == SUSPEND_ACKED) {
- as->suspend_result = err;
- as->suspend_state = SUSPEND_DONE;
- }
- }
- up_read(&user_list_lock);
- mutex_unlock(&state_lock);
-
- wake_up(&apm_suspend_waitqueue);
-}
-
static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
{
struct apm_user *as = fp->private_data;
@@ -307,25 +279,22 @@ apm_ioctl(struct inode * inode, struct f
as->suspend_result = -EINTR;
- if (as->suspend_state == SUSPEND_READ) {
- int pending;
-
+ switch (as->suspend_state) {
+ case SUSPEND_READ:
/*
* If we read a suspend command from /dev/apm_bios,
* then the corresponding APM_IOC_SUSPEND ioctl is
* interpreted as an acknowledge.
*/
as->suspend_state = SUSPEND_ACKED;
- suspends_pending--;
- pending = suspends_pending == 0;
+ atomic_dec(&suspend_acks_pending);
mutex_unlock(&state_lock);
/*
- * If there are no further acknowledges required,
- * suspend the system.
+ * suspend_acks_pending changed, the notifier needs to
+ * be woken up for this
*/
- if (pending)
- apm_suspend();
+ wake_up(&apm_suspend_waitqueue);
/*
* Wait for the suspend/resume to complete. If there
@@ -341,35 +310,21 @@ apm_ioctl(struct inode * inode, struct f
* try_to_freeze() in freezer_count() will not trigger
*/
freezer_count();
- } else {
+ break;
+ case SUSPEND_ACKTO:
+ as->suspend_result = -ETIMEDOUT;
+ mutex_unlock(&state_lock);
+ break;
+ default:
as->suspend_state = SUSPEND_WAIT;
mutex_unlock(&state_lock);
/*
* Otherwise it is a request to suspend the system.
- * Queue an event for all readers, and expect an
- * acknowledge from all writers who haven't already
- * acknowledged.
- */
- err = queue_suspend_event(APM_USER_SUSPEND, as);
- if (err < 0) {
- /*
- * Avoid taking the lock here - this
- * should be fine.
- */
- as->suspend_state = SUSPEND_NONE;
- break;
- }
-
- if (err > 0)
- apm_suspend();
-
- /*
- * Wait for the suspend/resume to complete. If there
- * are pending acknowledges, we wait here for them.
+ * Just invoke pm_suspend(), we'll handle it from
+ * there via the notifier.
*/
- wait_event_freezable(apm_suspend_waitqueue,
- as->suspend_state == SUSPEND_DONE);
+ as->suspend_result = pm_suspend(PM_SUSPEND_MEM);
}
mutex_lock(&state_lock);
@@ -385,7 +340,6 @@ apm_ioctl(struct inode * inode, struct f
static int apm_release(struct inode * inode, struct file * filp)
{
struct apm_user *as = filp->private_data;
- int pending = 0;
filp->private_data = NULL;
@@ -395,18 +349,15 @@ static int apm_release(struct inode * in
/*
* We are now unhooked from the chain. As far as new
- * events are concerned, we no longer exist. However, we
- * need to balance suspends_pending, which means the
- * possibility of sleeping.
+ * events are concerned, we no longer exist.
*/
mutex_lock(&state_lock);
- if (as->suspend_state != SUSPEND_NONE) {
- suspends_pending -= 1;
- pending = suspends_pending == 0;
- }
+ if (as->suspend_state == SUSPEND_PENDING ||
+ as->suspend_state == SUSPEND_READ)
+ atomic_dec(&suspend_acks_pending);
mutex_unlock(&state_lock);
- if (pending)
- apm_suspend();
+
+ wake_up(&apm_suspend_waitqueue);
kfree(as);
return 0;
@@ -542,7 +493,6 @@ static int kapmd(void *arg)
{
do {
apm_event_t event;
- int ret;
wait_event_interruptible(kapmd_wait,
!queue_empty(&kapmd_queue) || kthread_should_stop());
@@ -567,20 +517,13 @@ static int kapmd(void *arg)
case APM_USER_SUSPEND:
case APM_SYS_SUSPEND:
- ret = queue_suspend_event(event, NULL);
- if (ret < 0) {
- /*
- * We were busy. Try again in 50ms.
- */
- queue_add_event(&kapmd_queue, event);
- msleep(50);
- }
- if (ret > 0)
- apm_suspend();
+ pm_suspend(PM_SUSPEND_MEM);
break;
case APM_CRITICAL_SUSPEND:
- apm_suspend();
+ atomic_inc(&userspace_notification_inhibit);
+ pm_suspend(PM_SUSPEND_MEM);
+ atomic_dec(&userspace_notification_inhibit);
break;
}
} while (1);
@@ -588,6 +531,120 @@ static int kapmd(void *arg)
return 0;
}
+static int apm_suspend_notifier(struct notifier_block *nb,
+ unsigned long event,
+ void *dummy)
+{
+ struct apm_user *as;
+ int err;
+
+ /* short-cut emergency suspends */
+ if (atomic_read(&userspace_notification_inhibit))
+ return NOTIFY_DONE;
+
+ switch (event) {
+ case PM_SUSPEND_PREPARE:
+ /*
+ * Queue an event to all "writer" users that we want
+ * to suspend and need their ack.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state != SUSPEND_WAIT && as->reader &&
+ as->writer && as->suser) {
+ as->suspend_state = SUSPEND_PENDING;
+ atomic_inc(&suspend_acks_pending);
+ queue_add_event(&as->queue, APM_USER_SUSPEND);
+ }
+ }
+
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+ wake_up_interruptible(&apm_waitqueue);
+
+ /*
+ * Wait for the the suspend_acks_pending variable to drop to
+ * zero, meaning everybody acked the suspend event (or the
+ * process was killed.)
+ *
+ * If the app won't answer within a short while we assume it
+ * locked up and ignore it.
+ */
+ err = wait_event_interruptible_timeout(
+ apm_suspend_waitqueue,
+ atomic_read(&suspend_acks_pending) == 0,
+ 5*HZ);
+
+ /* timed out */
+ if (err == 0) {
+ /*
+ * Move anybody who timed out to "ack timeout" state.
+ *
+ * We could time out and the userspace does the ACK
+ * right after we time out but before we enter the
+ * locked section here, but that's fine.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state == SUSPEND_PENDING ||
+ as->suspend_state == SUSPEND_READ) {
+ as->suspend_state = SUSPEND_ACKTO;
+ atomic_dec(&suspend_acks_pending);
+ }
+ }
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+ }
+
+ /* let suspend proceed */
+ if (err >= 0)
+ return NOTIFY_OK;
+
+ /* interrupted by signal */
+ return NOTIFY_BAD;
+
+ case PM_POST_SUSPEND:
+ /*
+ * Anyone on the APM queues will think we're still suspended.
+ * Send a message so everyone knows we're now awake again.
+ */
+ queue_event(APM_NORMAL_RESUME);
+
+ /*
+ * Finally, wake up anyone who is sleeping on the suspend.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state == SUSPEND_ACKED) {
+ /*
+ * TODO: maybe grab error code, needs core
+ * changes to push the error to the notifier
+ * chain (could use the second parameter if
+ * implemented)
+ */
+ as->suspend_result = 0;
+ as->suspend_state = SUSPEND_DONE;
+ }
+ }
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+
+ wake_up(&apm_suspend_waitqueue);
+ return NOTIFY_OK;
+
+ default:
+ return NOTIFY_DONE;
+ }
+}
+
+static struct notifier_block apm_notif_block = {
+ .notifier_call = apm_suspend_notifier,
+};
+
static int __init apm_init(void)
{
int ret;
@@ -601,7 +658,7 @@ static int __init apm_init(void)
if (IS_ERR(kapmd_tsk)) {
ret = PTR_ERR(kapmd_tsk);
kapmd_tsk = NULL;
- return ret;
+ goto out;
}
wake_up_process(kapmd_tsk);
@@ -610,16 +667,27 @@ static int __init apm_init(void)
#endif
ret = misc_register(&apm_device);
- if (ret != 0) {
- remove_proc_entry("apm", NULL);
- kthread_stop(kapmd_tsk);
- }
+ if (ret)
+ goto out_stop;
+ ret = register_pm_notifier(&apm_notif_block);
+ if (ret)
+ goto out_unregister;
+
+ return 0;
+
+ out_unregister:
+ misc_deregister(&apm_device);
+ out_stop:
+ remove_proc_entry("apm", NULL);
+ kthread_stop(kapmd_tsk);
+ out:
return ret;
}
static void __exit apm_exit(void)
{
+ unregister_pm_notifier(&apm_notif_block);
misc_deregister(&apm_device);
remove_proc_entry("apm", NULL);
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