[PATCH v2] remoteproc: imx_dsp_rproc: Add mutex protection for workqueue

[Shengjiu Wang <shengjiu.wang@nxp.com>]

The workqueue may execute late even after remoteproc is stopped or
stopping, some resources (rpmsg device and endpoint) have been
released in rproc_stop_subdevices(), then rproc_vq_interrupt()
accessing these resources will cause kennel dump.

Call trace:
 virtqueue_add_split+0x1ac/0x560
 virtqueue_add_inbuf+0x4c/0x60
 rpmsg_recv_done+0x15c/0x294
 vring_interrupt+0x6c/0xa4
 rproc_vq_interrupt+0x30/0x50
 imx_dsp_rproc_vq_work+0x24/0x40 [imx_dsp_rproc]
 process_one_work+0x1d0/0x354
 worker_thread+0x13c/0x470
 kthread+0x154/0x160
 ret_from_fork+0x10/0x20

Add mutex protection in imx_dsp_rproc_vq_work(), if the state is
not running, then just skip calling rproc_vq_interrupt().

Also the flush workqueue operation can't be added in rproc stop
for the same reason. The call sequence is

rproc_shutdown
-> rproc_stop
   ->rproc_stop_subdevices
   ->rproc->ops->stop()
     ->imx_dsp_rproc_stop
       ->flush_work
         -> rproc_vq_interrupt

The resource needed by rproc_vq_interrupt has been released in
rproc_stop_subdevices, so flush_work is not safe to be called in
imx_dsp_rproc_stop.

Fixes: ec0e5549f358 ("remoteproc: imx_dsp_rproc: Add remoteproc driver for DSP on i.MX")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
---
changes in v2:
- update commit message

 drivers/remoteproc/imx_dsp_rproc.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/remoteproc/imx_dsp_rproc.c b/drivers/remoteproc/imx_dsp_rproc.c
index 899aa8dd12f0..95da1cbefacf 100644
--- a/drivers/remoteproc/imx_dsp_rproc.c
+++ b/drivers/remoteproc/imx_dsp_rproc.c
@@ -347,9 +347,6 @@ static int imx_dsp_rproc_stop(struct rproc *rproc)
 	struct device *dev = rproc->dev.parent;
 	int ret = 0;
 
-	/* Make sure work is finished */
-	flush_work(&priv->rproc_work);
-
 	if (rproc->state == RPROC_CRASHED) {
 		priv->flags &= ~REMOTE_IS_READY;
 		return 0;
@@ -432,9 +429,18 @@ static void imx_dsp_rproc_vq_work(struct work_struct *work)
 {
 	struct imx_dsp_rproc *priv = container_of(work, struct imx_dsp_rproc,
 						  rproc_work);
+	struct rproc *rproc = priv->rproc;
+
+	mutex_lock(&rproc->lock);
+
+	if (rproc->state != RPROC_RUNNING)
+		goto unlock_mutex;
 
 	rproc_vq_interrupt(priv->rproc, 0);
 	rproc_vq_interrupt(priv->rproc, 1);
+
+unlock_mutex:
+	mutex_unlock(&rproc->lock);
 }
 
 /**
-- 
2.34.1