From: Ranko Zivojnovic <ranko@spidernet.net>
Date: Tue, 17 Jul 2007 01:28:32 +0000 (-0700)
Subject: [NET]: gen_estimator deadlock fix
X-Git-Tag: v2.6.23-rc1~496^2~19
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0929c2dd83317813425b937fbc0041013b8685ff;p=pandora-kernel.git

[NET]: gen_estimator deadlock fix

-Fixes ABBA deadlock noted by Patrick McHardy <kaber@trash.net>:

> There is at least one ABBA deadlock, est_timer() does:
> read_lock(&est_lock)
> spin_lock(e->stats_lock) (which is dev->queue_lock)
>
> and qdisc_destroy calls htb_destroy under dev->queue_lock, which
> calls htb_destroy_class, then gen_kill_estimator and this
> write_locks est_lock.

To fix the ABBA deadlock the rate estimators are now kept on an rcu list.

-The est_lock changes the use from protecting the list to protecting
the update to the 'bstat' pointer in order to avoid NULL dereferencing.

-The 'interval' member of the gen_estimator structure removed as it is
not needed.

Signed-off-by: Ranko Zivojnovic <ranko@spidernet.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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