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Fix possibly deadlock condition

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3601 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2011-05-13 03:33:03 +00:00
parent 3e1e4f6876
commit 1c99e6b36b
1 changed files with 21 additions and 16 deletions
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37
drivers/usbhost/usbhost_storage.c
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@ -937,10 +937,6 @@ static void usbhost_destroy(FAR void *arg)
* On success, zero (OK) is returned. On a failure, a negated errno value is
* returned indicating the nature of the failure
*
* NOTE that the class instance remains valid upon return with a failure. It is
* the responsibility of the higher level enumeration logic to call
* CLASS_DISCONNECTED to free up the class driver resources.
*
* Assumptions:
* This function will *not* be called from an interrupt handler.
*
@ -1288,28 +1284,33 @@ static inline int usbhost_initvolume(FAR struct usbhost_state_s *priv)
usbhost_takesem(&priv->exclsem);
DEBUGASSERT(priv->crefs >= 2);
/* Decrement the reference count */
priv->crefs--;
/* Handle a corner case where (1) open() has been called so the
* reference count is > 2, but the device has been disconnected.
* reference count was > 2, but the device has been disconnected.
* In this case, the class instance needs to persist until close()
* is called.
*/
if (priv->crefs <= 2 && priv->disconnected)
if (priv->crefs <= 1 && priv->disconnected)
{
/* We don't have to give the semaphore because it will be
* destroyed when usb_destroy is called.
/* The will cause the enumeration logic to disconnect
* the class driver.
*/
ret = -ENODEV;
}
else
{
/* Ready for normal operation as a block device driver */
uvdbg("Successfully initialized\n");
priv->crefs--;
usbhost_givesem(&priv->exclsem);
}
/* Release the semaphore... there is a race condition here.
* Decrementing the reference count and releasing the semaphore
* allows usbhost_destroy() to execute (on the worker thread);
* the class driver instance could get destoryed before we are
* ready to handle it!
*/
usbhost_givesem(&priv->exclsem);
}
return ret;
@ -1671,6 +1672,10 @@ static FAR struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *d
* On success, zero (OK) is returned. On a failure, a negated errno value is
* returned indicating the nature of the failure
*
* NOTE that the class instance remains valid upon return with a failure. It is
* the responsibility of the higher level enumeration logic to call
* CLASS_DISCONNECTED to free up the class driver resources.
*
* Assumptions:
* - This function will *not* be called from an interrupt handler.
* - If this function returns an error, the USB host controller driver