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[media] vb2: fix vb2_thread_stop race conditions 

The locking scheme inside the vb2 thread is unsafe when stopping the
thread. In particular kthread_stop was called *after* internal data
structures were cleaned up instead of doing that before. In addition,
internal vb2 functions were called after threadio->stop was set to
true and vb2_internal_streamoff was called. This is also not allowed.

All this led to a variety of race conditions and kernel warnings and/or
oopses.

Fixed by moving the kthread_stop call up before the cleanup takes
place, and by checking threadio->stop before calling internal vb2
queuing operations.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: <stable@vger.kernel.org>      # for v3.16 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Hans Verkuil 2015-01-19 06:16:18 -03:00 committed by Mauro Carvalho Chehab
parent 42d74e4fe6
commit 6cf11ee630
1 changed files with 9 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/media/v4l2-core/videobuf2-core.c
View File

@ -3146,27 +3146,26 @@ static int vb2_thread(void *data)
prequeue--;
} else {
call_void_qop(q, wait_finish, q);
if (!threadio->stop)
ret = vb2_internal_dqbuf(q, &fileio->b, 0);
call_void_qop(q, wait_prepare, q);
dprintk(5, "file io: vb2_dqbuf result: %d\n", ret);
}
if (threadio->stop)
break;
if (ret)
if (ret || threadio->stop)
break;
try_to_freeze();
vb = q->bufs[fileio->b.index];
if (!(fileio->b.flags & V4L2_BUF_FLAG_ERROR))
ret = threadio->fnc(vb, threadio->priv);
if (ret)
if (threadio->fnc(vb, threadio->priv))
break;
call_void_qop(q, wait_finish, q);
if (set_timestamp)
v4l2_get_timestamp(&fileio->b.timestamp);
if (!threadio->stop)
ret = vb2_internal_qbuf(q, &fileio->b);
call_void_qop(q, wait_prepare, q);
if (ret)
if (ret || threadio->stop)
break;
}
@ -3235,11 +3234,11 @@ int vb2_thread_stop(struct vb2_queue *q)
threadio->stop = true;
vb2_internal_streamoff(q, q->type);
call_void_qop(q, wait_prepare, q);
err = kthread_stop(threadio->thread);
q->fileio = NULL;
fileio->req.count = 0;
vb2_reqbufs(q, &fileio->req);
kfree(fileio);
err = kthread_stop(threadio->thread);
threadio->thread = NULL;
kfree(threadio);
q->fileio = NULL;