From: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Thu, 30 Jul 2015 05:27:13 +0000 (-0700)
Subject: target: Perform RCU callback barrier before backend/fabric unload
X-Git-Tag: omap-for-v4.3/fixes-merge-window~80^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9450918293b3c35f11883231a53da1aed2c78403;p=pandora-kernel.git

target: Perform RCU callback barrier before backend/fabric unload

This patch addresses a v4.2-rc1 regression where backend driver
module unload happening immediately after TBO->free_device()
does internal call_rcu(), will currently result in IRQ context
rcu_process_callbacks() use-after-free paging OOPsen.

It adds the missing rcu_barrier() in target_backend_unregister()
to perform an explicit RCU barrier waiting for all RCU callbacks
to complete before releasing target_backend_ops memory, and
allowing TBO->module exit to proceed.

Also, do the same for fabric drivers in target_unregister_template()
to ensure se_deve_entry->rcu_head -> kfree_rcu() callbacks have
completed, before allowing target_core_fabric_ops->owner module
exit to proceed.

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---

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