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Date: Mon, 1 Dec 2014 22:33:57 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Paul E.McKenney" <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, Waiman Long <Waiman.Long@hp.com>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 0/1] x86, ticketlock: spin_unlock_wait() can livelock
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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.

Oleg.