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Subject[patch][2/4] ibmasm driver: correctly wake up sleeping threads
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This is the second of four patches for the ibmasm driver:

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>


diff -urN linux-2.6.12-rc6.test/drivers/misc/ibmasm/event.c linux-2.6.12-rc6.ibmasm/drivers/misc/ibmasm/event.c
--- linux-2.6.12-rc6.test/drivers/misc/ibmasm/event.c 2005-06-08 18:34:06.517588168 -0700
+++ linux-2.6.12-rc6.ibmasm/drivers/misc/ibmasm/event.c 2005-06-08 17:54:09.525986280 -0700
@@ -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 @@
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 @@
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 @@
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 @@
{
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 @@

void ibmasm_event_buffer_exit(struct service_processor *sp)
{
- wake_up_event_readers(sp);
kfree(sp->event_buffer);
}
--- linux-2.6.12-rc6.test/drivers/misc/ibmasm/ibmasmfs.c 2005-06-08 18:34:06.518588016 -0700
+++ linux-2.6.12-rc6.ibmasm/drivers/misc/ibmasm/ibmasmfs.c 2005-06-08 17:54:09.533985064 -0700
@@ -374,6 +374,7 @@
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 @@
{
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 @@
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 @@
if (*offset != 0)
return 0;

- wake_up_interruptible(&event_data->reader.wait);
+ ibmasm_cancel_next_event(&event_data->reader);
return 0;
}

--- linux-2.6.12-rc6.test/drivers/misc/ibmasm/ibmasm.h 2005-06-08 18:40:46.069846992 -0700
+++ linux-2.6.12-rc6.ibmasm/drivers/misc/ibmasm/ibmasm.h 2005-06-08 17:54:09.534984912 -0700
@@ -108,6 +189,7 @@
};

struct event_reader {
+ int cancelled;
unsigned int next_serial_number;
wait_queue_head_t wait;
struct list_head node;
@@ -185,6 +267,7 @@
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);

-
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