| Message ID | 20241226025319.1724209-1-Leo-Yang@quantatw.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] mctp i3c: fix MCTP I3C driver multi-thread issue | expand |
diff --git a/drivers/net/mctp/mctp-i3c.c b/drivers/net/mctp/mctp-i3c.c index 9adad59b8676..0d625b351ebd 100644 --- a/drivers/net/mctp/mctp-i3c.c +++ b/drivers/net/mctp/mctp-i3c.c @@ -125,6 +125,7 @@ static int mctp_i3c_read(struct mctp_i3c_device *mi) xfer.data.in = skb_put(skb, mi->mrl); + mutex_lock(&mi->lock); rc = i3c_device_do_priv_xfers(mi->i3c, &xfer, 1); if (rc < 0) goto err; @@ -166,8 +167,10 @@ static int mctp_i3c_read(struct mctp_i3c_device *mi) stats->rx_dropped++; } + mutex_unlock(&mi->lock); return 0; err: + mutex_unlock(&mi->lock); kfree_skb(skb); return rc; }
We found a timeout problem with the pldm command on our system. The reason is that the MCTP-I3C driver has a race condition when receiving multiple-packet messages in multi-thread, resulting in a wrong packet order problem. We identified this problem by adding a debug message to the mctp_i3c_read function. According to the MCTP spec, a multiple-packet message must be composed in sequence, and if there is a wrong sequence, the whole message will be discarded and wait for the next SOM. For example, SOM → Pkt Seq #2 → Pkt Seq #1 → Pkt Seq #3 → EOM. Therefore, we try to solve this problem by adding a mutex to the mctp_i3c_read function. Before the modification, when a command requesting a multiple-packet message response is sent consecutively, an error usually occurs within 100 loops. After the mutex, it can go through 40000 loops without any error, and it seems to run well. But I'm a little worried about the performance of mutex in high load situation (as spec seems to allow different endpoints to respond at the same time), do you think this is a feasible solution? Signed-off-by: Leo Yang <Leo-Yang@quantatw.com> --- drivers/net/mctp/mctp-i3c.c | 3 +++ 1 file changed, 3 insertions(+)