[PATCH 0/1] x86, ticketlock: spin_unlock_wait() can livelock
From: Oleg Nesterov
Date: Mon Dec 01 2014 - 16:34:49 EST
Please review, I'm afraid I could miss something.
OTOH, this almost looks like a bug to me. And in fact I have a bug
report which looks as if spin_unlock_wait() actually spins "forever"
until the system panics, although most probably the are other problems
in kernel/sched which lead to rq->lock contention.
Do we need a barrier() in arch_spin_unlock_wait() ? I guess no, and
the current code doesn't have it.
Perhaps it should use __ticket_lock_spinning() like arch_spin_lock() ?
And probably we should add the lockdep annotations.
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