TDB lock contention during "startup" event caused winbind crash

[Kenny Dinh]

Hello,

I ran into a situation where contention for tdb lock caused "winbind" to
crash. Below is the scenario

-- ctdb process                       smbd process           winbindd
process

-- "service start winbind"------------------------------         winbindd
 started (pid 14461)
-- "service start smb" ------ smbd started ( pid 14602)
-------------------------------------- smbd acquires lock g_lock.tdb - hung
-- invoke hung script ------  smbd child pid (14602) is still hung
-- ----------------------------------- smbd still lock g_lock.tdb
-- CTDB restart all services
-- kill existing winbindd ------------------------------------------
winbindd (pid 14461 term)
-- service start winbind ---------------------------------------- winbindd
started (pid 14733)
-- 
 -----------------------------------------------------------------------try
to lock g_lock.tdb but failed
-- 
 ------------------------------------------------------------------------
PANIC
--  kill existing smbd -------- Kill pid 14602
--  service start smb ------- smbd started

Attached are log file from ctdb, winbind, and smb, and winbind core
backtrace.

My propose patch is to make sure all winbindd, smbd, and nmbd services are
terminated at the beginning of "startup" event.

Thanks for looking,
~Kenny
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