kern/149586: _callout_stop_safe prematurely unsets CALLOUT_ACTIVE

[John Giacomoni]

>Number:         149586
>Category:       kern
>Synopsis:       _callout_stop_safe prematurely unsets CALLOUT_ACTIVE
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Aug 12 18:40:03 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     John Giacomoni
>Release:        7.3/8.1
>Organization:
LineRate Systems
>Environment:
>Description:
in kern/kern_timeout.c
_callout_stop_safe(c, 0) prematurely unsets CALLOUT_ACTIVE on inflight callouts making it impossible to know when a callout is actually stopped (one cannot spin on callout_active() to know when it is drained/dead/idle).

This is problematic for unsleepable threads that need to deallocate an object shared with a callout but cannot call callout_drain to guarantee that the reference has been implicitly freed.

>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: