From 63faabfd89f4db9862ae2a663193e511419c67eb Mon Sep 17 00:00:00 2001
From: Hans Verkuil <hans.verkuil@cisco.com>
Date: Fri, 13 Dec 2013 13:13:40 -0300
Subject: [PATCH] [media] vb2: fix race condition between REQBUFS and
 QBUF/PREPARE_BUF

When preparing a buffer the queue lock is released for a short while
if the memory mode is USERPTR (see __buf_prepare for the details), which
would allow a race with a REQBUFS which can free the buffers. Removing the
buffers from underneath __buf_prepare is obviously a bad idea, so we
check if any of the buffers is in the state PREPARING, and if so we
just return -EAGAIN.

If this happens, then the application does something really strange. The
REQBUFS call can be retried safely, since this situation is transient.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
---
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