[PATCH 4/4] usb: libusual: locking cleanup

[Andrew Morton]

I converted the usu_init_notify semaphore to normal mutex usage, and it
should still prevent the request_module before the init routine is
complete. Before it acted more like a complete, now the mutex protects
two distinct section from running at the same time..
---
drivers/usb/storage/libusual.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
Index: linux-2.6.23/drivers/usb/storage/libusual.c
===================================================================
--- linux-2.6.23.orig/drivers/usb/storage/libusual.c
+++ linux-2.6.23/drivers/usb/storage/libusual.c
@@ -9,6 +9,7 @@
#include <linux/usb_usual.h>
#include <linux/vmalloc.h>
#include <linux/kthread.h>
+#include <linux/mutex.h>
/*
*/
@@ -30,7 +31,7 @@ static atomic_t usu_bias = ATOMIC_INIT(U
#define BIAS_NAME_SIZE (sizeof("usb-storage"))
static const char *bias_names[3] = { "none", "usb-storage", "ub" };
-static struct semaphore usu_init_notify;
+static DEFINE_MUTEX(usu_probe_mutex);
static DECLARE_COMPLETION(usu_end_notify);
static atomic_t total_threads = ATOMIC_INIT(0);
@@ -178,10 +179,7 @@ static int usu_probe_thread(void *arg)
int rc;
unsigned long flags;
- /* A completion does not work here because it's counted. */
- down(&usu_init_notify);
- up(&usu_init_notify);
-
+ mutex_lock(&usu_probe_mutex);
rc = request_module(bias_names[type]);
spin_lock_irqsave(&usu_lock, flags);
if (rc == 0 && (st->fls & USU_MOD_FL_PRESENT) == 0) {
@@ -194,6 +192,7 @@ static int usu_probe_thread(void *arg)
}
st->fls &= ~USU_MOD_FL_THREAD;
spin_unlock_irqrestore(&usu_lock, flags);
+ mutex_unlock(&usu_probe_mutex);
complete_and_exit(&usu_end_notify, 0);
}
@@ -204,10 +203,9 @@ static int __init usb_usual_init(void)
{
int rc;
- sema_init(&usu_init_notify, 0);
-
+ mutex_lock(&usu_probe_mutex);
rc = usb_register(&usu_driver);
- up(&usu_init_notify);
+ mutex_unlock(&usu_probe_mutex);
return rc;
}

That's some pretty hairy-looking code you're playing with there. Has this
been runtime tested?


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