Hi,
I recently saw an article in Linux Journal about writing a USB device
driver. One thing that leapt out at me was that the skeleton driver
code called MOD_INC_USE_COUNT and MOD_DEC_USE_COUNT in the
file_operations open and release methods. Aren't these macros Linux
2.2-isms that have been made redundant by the file_operations.owner
field? Since the owner field is already correctly set to THIS_MODULE,
I have attached a patch to remove the MOD_XXX_USE_COUNT macro
calls. After all, asking a module to lock itself has an implicit race
condition.
This patch is against Linux 2.4.16.
Cheers,
Chris
--- drivers/usb/usb-skeleton.c.orig Tue Dec 4 13:05:28 2001
+++ drivers/usb/usb-skeleton.c Tue Dec 4 13:06:42 2001
@@ -215,15 +215,11 @@
return -ENODEV;
}
- /* increment our usage count for the module */
- MOD_INC_USE_COUNT;
-
/* lock our minor table and get our local data for this minor */
down (&minor_table_mutex);
dev = minor_table[subminor];
if (dev == NULL) {
up (&minor_table_mutex);
- MOD_DEC_USE_COUNT;
return -ENODEV;
}
@@ -278,7 +274,6 @@
/* the device was unplugged before the file was released */
up (&dev->sem);
skel_delete (dev);
- MOD_DEC_USE_COUNT;
up (&minor_table_mutex);
return 0;
}
@@ -290,9 +285,6 @@
usb_unlink_urb (dev->write_urb);
dev->open_count = 0;
}
-
- /* decrement our usage count for the module */
- MOD_DEC_USE_COUNT;
exit_not_opened:
up (&dev->sem);
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