From: Pavel Emelyanov <xemul@openvz.org>
Date: Sat, 3 May 2008 00:49:39 +0000 (-0700)
Subject: bonding: Deadlock between bonding_store_bonds and bond_destroy_sysfs.
X-Git-Tag: v2.6.26-rc2~23^2~2^2~17
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ae68c39819ddf30549652962768a50edae5eec6f;p=pandora-kernel.git

bonding: Deadlock between bonding_store_bonds and bond_destroy_sysfs.

The sysfs layer has an internal protection, that ensures, that
all the process sitting inside ->sore/->show callback exits
before the appropriate entry is unregistered (the calltraces
are rather big, but I can provide them if required).

On the other hand, bonding takes rtnl_lock in
a) the bonding_store_bonds, i.e. in ->store callback,
b) module exit before calling the sysfs unregister routines.

Thus, the classical AB-BA deadlock may occur. To reproduce run
# while :; do modprobe bonding; rmmod bonding; done
and
# while :; do echo '+bond%d' > /sys/class/net/bonding_masters ; done
in parallel.

The fix is to move the bond_destroy_sysfs out of the rtnl_lock,
but _before_ bond_free_all to make sure no bonding devices exist
after module unload.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
---

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