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authorAlan Stern <stern@rowland.harvard.edu>2012-03-28 16:13:28 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-04-06 13:54:00 -0700
commitda8bfb090c2b30af9f3879443355f7eb1d0fe10a (patch)
tree377d67c3c0cc1ad40d7357f821712c4c9ba6c639 /drivers/usb/core
parentbcf398537630bf20b4dbe59ba855b69f404c93cf (diff)
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USB documentation: explain lifetime rules for unlinking URBs
This patch (as1534c) updates the documentation for usb_unlink_urb and related functions. It explains that the caller must prevent the URB being unlinked from getting deallocated while the unlink is taking place. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/core')
-rw-r--r--drivers/usb/core/urb.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 7239a73c1b8c..cd9b3a2cd8a7 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -539,6 +539,10 @@ EXPORT_SYMBOL_GPL(usb_submit_urb);
* never submitted, or it was unlinked before, or the hardware is already
* finished with it), even if the completion handler has not yet run.
*
+ * The URB must not be deallocated while this routine is running. In
+ * particular, when a driver calls this routine, it must insure that the
+ * completion handler cannot deallocate the URB.
+ *
* Unlinking and Endpoint Queues:
*
* [The behaviors and guarantees described below do not apply to virtual
@@ -603,6 +607,10 @@ EXPORT_SYMBOL_GPL(usb_unlink_urb);
* with error -EPERM. Thus even if the URB's completion handler always
* tries to resubmit, it will not succeed and the URB will become idle.
*
+ * The URB must not be deallocated while this routine is running. In
+ * particular, when a driver calls this routine, it must insure that the
+ * completion handler cannot deallocate the URB.
+ *
* This routine may not be used in an interrupt context (such as a bottom
* half or a completion handler), or when holding a spinlock, or in other
* situations where the caller can't schedule().
@@ -640,6 +648,10 @@ EXPORT_SYMBOL_GPL(usb_kill_urb);
* with error -EPERM. Thus even if the URB's completion handler always
* tries to resubmit, it will not succeed and the URB will become idle.
*
+ * The URB must not be deallocated while this routine is running. In
+ * particular, when a driver calls this routine, it must insure that the
+ * completion handler cannot deallocate the URB.
+ *
* This routine may not be used in an interrupt context (such as a bottom
* half or a completion handler), or when holding a spinlock, or in other
* situations where the caller can't schedule().