From: David Vrabel <david.vrabel@citrix.com>
Date: Fri, 16 May 2014 11:26:04 +0000 (+0100)
Subject: xen-netback: fix race between napi_complete() and interrupt handler
X-Git-Tag: omap-for-v3.16/fixes-against-rc1~146^2~22
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0d08fceb2e21c30ca3e1e462e678723f806acf18;p=pandora-kernel.git

xen-netback: fix race between napi_complete() and interrupt handler

When the NAPI budget was not all used, xenvif_poll() would call
napi_complete() /after/ enabling the interrupt.  This resulted in a
race between the napi_complete() and the napi_schedule() in the
interrupt handler.  The use of local_irq_save/restore() avoided by
race iff the handler is running on the same CPU but not if it was
running on a different CPU.

Fix this properly by calling napi_complete() before reenabling
interrupts (in the xenvif_napi_schedule_or_enable_irq() call).

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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