[PATCH] ibmasm driver: correctly wake up sleeping threads

Due to my incomplete understanding of the wait_event_interruptible() function
threads waiting for service processor events were not woken up.  This patch
fixes that problem.
Signed-off-by: Max Asbock <masbock@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/misc/ibmasm/event.c

@@ -23,6 +23,7 @@
  */
 
 #include "ibmasm.h"
+#include "lowlevel.h"
 
 /*
  * ASM service processor event handling routines.
@@ -34,7 +35,6 @@
  * circular buffer.
  */
 
-
 static void wake_up_event_readers(struct service_processor *sp)
 {
 	struct event_reader *reader;
@@ -63,7 +63,7 @@ void ibmasm_receive_event(struct service_processor *sp, void *data, unsigned int
 	spin_lock_irqsave(&sp->lock, flags);
 	/* copy the event into the next slot in the circular buffer */
 	event = &buffer->events[buffer->next_index];
-	memcpy(event->data, data, data_size);
+	memcpy_fromio(event->data, data, data_size);
 	event->data_size = data_size;
 	event->serial_number = buffer->next_serial_number;
 
@@ -93,7 +93,10 @@ int ibmasm_get_next_event(struct service_processor *sp, struct event_reader *rea
 	unsigned int index;
 	unsigned long flags;
 
-	if (wait_event_interruptible(reader->wait, event_available(buffer, reader)))
+	reader->cancelled = 0;
+
+	if (wait_event_interruptible(reader->wait,
+			event_available(buffer, reader) || reader->cancelled))
 		return -ERESTARTSYS;
 
 	if (!event_available(buffer, reader))
@@ -116,6 +119,12 @@ int ibmasm_get_next_event(struct service_processor *sp, struct event_reader *rea
 	return event->data_size;
 }
 
+void ibmasm_cancel_next_event(struct event_reader *reader)
+{
+        reader->cancelled = 1;
+        wake_up_interruptible(&reader->wait);
+}
+
 void ibmasm_event_reader_register(struct service_processor *sp, struct event_reader *reader)
 {
 	unsigned long flags;
@@ -131,8 +140,6 @@ void ibmasm_event_reader_unregister(struct service_processor *sp, struct event_r
 {
 	unsigned long flags;
 
-	wake_up_interruptible(&reader->wait);
-
 	spin_lock_irqsave(&sp->lock, flags);
 	list_del(&reader->node);
 	spin_unlock_irqrestore(&sp->lock, flags);
@@ -164,6 +171,5 @@ int ibmasm_event_buffer_init(struct service_processor *sp)
 
 void ibmasm_event_buffer_exit(struct service_processor *sp)
 {
-	wake_up_event_readers(sp);
 	kfree(sp->event_buffer);
 }

drivers/misc/ibmasm/ibmasm.h

@@ -108,6 +108,7 @@ struct event_buffer {
 };
 
 struct event_reader {
+	int			cancelled;
 	unsigned int		next_serial_number;
 	wait_queue_head_t	wait;
 	struct list_head	node;
@@ -185,6 +186,7 @@ extern void ibmasm_receive_event(struct service_processor *sp, void *data,  unsi
 extern void ibmasm_event_reader_register(struct service_processor *sp, struct event_reader *reader);
 extern void ibmasm_event_reader_unregister(struct service_processor *sp, struct event_reader *reader);
 extern int ibmasm_get_next_event(struct service_processor *sp, struct event_reader *reader);
+extern void ibmasm_cancel_next_event(struct event_reader *reader);
 
 /* heartbeat - from SP to OS */
 extern void ibmasm_register_panic_notifier(void);

drivers/misc/ibmasm/ibmasmfs.c

@@ -374,6 +374,7 @@ static int event_file_open(struct inode *inode, struct file *file)
 	ibmasm_event_reader_register(sp, &event_data->reader);
 
 	event_data->sp = sp;
+	event_data->active = 0;
 	file->private_data = event_data;
 	return 0;
 }
@@ -391,7 +392,9 @@ static ssize_t event_file_read(struct file *file, char __user *buf, size_t count
 {
 	struct ibmasmfs_event_data *event_data = file->private_data;
 	struct event_reader *reader = &event_data->reader;
+	struct service_processor *sp = event_data->sp;
 	int ret;
+	unsigned long flags;
 
 	if (*offset < 0)
 		return -EINVAL;
@@ -400,17 +403,32 @@ static ssize_t event_file_read(struct file *file, char __user *buf, size_t count
 	if (*offset != 0)
 		return 0;
 
-	ret = ibmasm_get_next_event(event_data->sp, reader);
+	spin_lock_irqsave(&sp->lock, flags);
+	if (event_data->active) {
+		spin_unlock_irqrestore(&sp->lock, flags);
+		return -EBUSY;
+	}
+	event_data->active = 1;
+	spin_unlock_irqrestore(&sp->lock, flags);
+
+	ret = ibmasm_get_next_event(sp, reader);
 	if (ret <= 0)
-		return ret;
+		goto out;
 
-	if (count < reader->data_size)
-		return -EINVAL;
+	if (count < reader->data_size) {
+		ret = -EINVAL;
+		goto out;
+	}
 
-        if (copy_to_user(buf, reader->data, reader->data_size))
-		return -EFAULT;
+        if (copy_to_user(buf, reader->data, reader->data_size)) {
+		ret = -EFAULT;
+		goto out;
+	}
+	ret = reader->data_size;
 
-	return reader->data_size;
+out:
+	event_data->active = 0;
+	return ret;
 }
 
 static ssize_t event_file_write(struct file *file, const char __user *buf, size_t count, loff_t *offset)
@@ -424,7 +442,7 @@ static ssize_t event_file_write(struct file *file, const char __user *buf, size_
 	if (*offset != 0)
 		return 0;
 
-	wake_up_interruptible(&event_data->reader.wait);
+	ibmasm_cancel_next_event(&event_data->reader);
 	return 0;
 }