From: David S. Miller <davem@davemloft.net>
Date: Tue, 19 Aug 2008 11:00:36 +0000 (-0700)
Subject: pkt_sched: Prevent livelock in TX queue running.
X-Git-Tag: v2.6.27-rc4~39^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=195648bbc5ae0848e82f771ecf4cd7497054c212;p=pandora-kernel.git

pkt_sched: Prevent livelock in TX queue running.

If dev_deactivate() is trying to quiesce the queue, it
is theoretically possible for another cpu to livelock
trying to process that queue.  This happens because
dev_deactivate() grabs the queue spinlock as it checks
the queue state, whereas net_tx_action() does a trylock
and reschedules the qdisc if it hits the lock.

This breaks the livelock by adding a check on
__QDISC_STATE_DEACTIVATED to net_tx_action() when
the trylock fails.

Based upon feedback from Herbert Xu and Jarek Poplawski.

Signed-off-by: David S. Miller <davem@davemloft.net>
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