When a DBC is released, the device sends a QAIC_TRANS_DEACTIVATE_FROM_DEV
transaction to the host over the QAIC_CONTROL MHI channel. QAIC handles
this by calling decode_deactivate() to release the resources allocated for
that DBC. Since that handling is done in the qaic_manage_ioctl() context,
if the user goes away before receiving and handling the deactivation, the
host will be out-of-sync with the DBCs available for use, and the DBC
resources will not be freed unless the device is removed. If another user
loads and requests to activate a network, then the device assigns the same
DBC to that network, QAIC will "indefinitely" wait for dbc->in_use = false,
leading the user process to hang.
As a solution to this, handle QAIC_TRANS_DEACTIVATE_FROM_DEV transactions
that are received after the user has gone away.
Fixes: 129776ac2e38 ("accel/qaic: Add control path")
Signed-off-by: Youssef Samir <[email protected]>
---
drivers/accel/qaic/qaic_control.c | 46 +++++++++++++++++++++++++++++--
1 file changed, 44 insertions(+), 2 deletions(-)
diff --git a/drivers/accel/qaic/qaic_control.c
b/drivers/accel/qaic/qaic_control.c
index 428d8f65bff3..16bdae028935 100644
--- a/drivers/accel/qaic/qaic_control.c
+++ b/drivers/accel/qaic/qaic_control.c
@@ -913,7 +913,7 @@ static int decode_deactivate(struct qaic_device *qdev, void
*trans, u32 *msg_len
*/
return -ENODEV;
- if (status) {
+ if (usr && status) {
/*
* Releasing resources failed on the device side, which puts
* us in a bind since they may still be in use, so enable the
@@ -1108,6 +1108,9 @@ static void *msg_xfer(struct qaic_device *qdev, struct
wrapper_list *wrappers, u
mutex_lock(&qdev->cntl_mutex);
if (!list_empty(&elem.list))
list_del(&elem.list);
+ /* resp_worker() processed the response but the wait was interrupted */
+ else if (list_empty(&elem.list) && ret == -ERESTARTSYS)
+ ret = 0;
if (!ret && !elem.buf)
ret = -ETIMEDOUT;
else if (ret > 0 && !elem.buf)
@@ -1418,7 +1421,46 @@ static void resp_worker(struct work_struct *work)
}
mutex_unlock(&qdev->cntl_mutex);
- if (!found)
+ if (!found) {
+ /*
+ * The user might have gone away at this point without waiting
+ * for QAIC_TRANS_DEACTIVATE_FROM_DEV transaction coming from
+ * the device. If this is not handled correctly, the host will
+ * not know that the DBC[n] has been freed on the device.
+ * Due to this failure in synchronization between the device and
+ * the host, if another user requests to activate a network, and
+ * the device assigns DBC[n] again, save_dbc_buf() will hang,
+ * waiting for dbc[n]->in_use to be set to false, which will not
+ * happen unless the qaic_dev_reset_clean_local_state() gets
+ * called by resetting the device (or re-inserting the module).
+ *
+ * As a solution, we look for QAIC_TRANS_DEACTIVATE_FROM_DEV
+ * transactions in the message before disposing of it, then
+ * handle releasing the DBC resources.
+ *
+ * Since the user has gone away, if the device could not
+ * deactivate the network (status != 0), there is no way to
+ * enable and reassign the DBC to the user. We can put trust in
+ * the device that it will release all the active DBCs in
+ * response to the QAIC_TRANS_TERMINATE_TO_DEV transaction,
+ * otherwise, the user can issue an soc_reset to the device.
+ */
+ u32 msg_count = le32_to_cpu(msg->hdr.count);
+ u32 msg_len = le32_to_cpu(msg->hdr.len);
+ u32 len = 0;
+ int j;
+
+ for (j = 0; j < msg_count && len < msg_len; ++j) {
+ struct wire_trans_hdr *trans_hdr;
+
+ trans_hdr = (struct wire_trans_hdr *)(msg->data + len);
+ if (le32_to_cpu(trans_hdr->type) ==
QAIC_TRANS_DEACTIVATE_FROM_DEV) {
+ if (decode_deactivate(qdev, trans_hdr, &len,
NULL))
+ len += le32_to_cpu(trans_hdr->len);
+ } else {
+ len += le32_to_cpu(trans_hdr->len);
+ }
+ }
/* request must have timed out, drop packet */
kfree(msg);
--
2.43.0
