usb/80777: usb_rem_task() should wait for callback to complete

[Hans Petter Selasky]

>Number:         80777
>Category:       usb
>Synopsis:       usb_rem_task() should wait for callback to complete?
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    freebsd-usb
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun May 08 13:50:07 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     HPS
>Release:        FreeBSD 6.0-CURRENT i386
>Organization:
>Environment:
System: FreeBSD 6.0-CURRENT FreeBSD 6.0-CURRENT #45: Mon Mar 21 15:40:17 CET 
2005 root@:/usr/obj/usr/src/sys/custom i386

>Description:
In the file "/sys/dev/usb/usb.c", the function "usb_rem_task" should wait for 
the "usb_task_thread()" to finish execution of the callback function. Though 
this might be impossible due to the contexts from which this function is 
called. At least one place (see if_udav.c) "usb_rem_task" is called from 
detach, and the code expects that the callback has returned or is not called, 
after that "usb_rem_task" returns. Else the callback will access freed 
memory. 

>How-To-Repeat:

>Fix:

Maybe "usb_xxxx_task" should not be used by if_udav.c, like suggested 
in another PR?
>Release-Note:
>Audit-Trail:
>Unformatted: