Re: [PATCH] rpmsg: glink: smem: order FIFO read after availability check

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 6/18/26 9:16 AM, Chunkai Deng wrote:
> glink_smem_rx_peek() reads the RX FIFO payload after the caller has
> determined data is available via glink_smem_rx_avail(), which reads the
> remote-updated head index. A control dependency between the head read
> and the subsequent payload read does not order the two loads, so the
> CPU may speculatively read the FIFO before observing the head update
> and consume stale data the remote has not yet published.
> 
> Add rmb() in glink_smem_rx_peek() before the memcpy_fromio() so the
> availability (head) read is ordered ahead of the FIFO payload read,
> matching the consumer pattern in
> Documentation/core-api/circular-buffers.rst.
> 
> Fixes: caf989c350e8 ("rpmsg: glink: Introduce glink smem based transport")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chunkai Deng <chunkai.deng@oss.qualcomm.com>
> ---

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad