[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>

1 files changed, 26 insertions, 8 deletions

diff --git a/drivers/misc/ibmasm/ibmasmfs.c b/drivers/misc/ibmasm/ibmasmfs.c
index 866e867e68f2..c87ef7d82b70 100644
--- a/drivers/misc/ibmasm/ibmasmfs.c
+++ b/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;
 }