Sorry, I`ll use a real name in patch v2.
I don't think this is a TOCTOU question.
The original code works fine when compiled with the -O3 option.
At this point the compiler will optimize to one memory access.
But when compiled with -O0, there will be two memory accesses, which is wrong.
This change was modified with reference to the rte_eth_tx_burst function.
On Wed, 4 Mar 2020 22:05:43 +0800
Tencent TGW team <quze...@gmail.com> wrote:
> When compiling with -O0,
> the compiler does not optimize two memory accesses into one.
> Leads to accessing a null pointer when calling the RX callback.
> The way to access the TX callback is correct.
>
> Signed-off-by: Tencent TGW team <tgw_t...@tencent.com>
> ---
> lib/librte_ethdev/rte_ethdev.h | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
> index d1a593ad1..35eb580ff 100644
> --- a/lib/librte_ethdev/rte_ethdev.h
> +++ b/lib/librte_ethdev/rte_ethdev.h
> @@ -4388,10 +4388,8 @@ rte_eth_rx_burst(uint16_t port_id, uint16_t queue_id,
> rx_pkts, nb_pkts);
>
> #ifdef RTE_ETHDEV_RXTX_CALLBACKS
> - if (unlikely(dev->post_rx_burst_cbs[queue_id] != NULL)) {
> - struct rte_eth_rxtx_callback *cb =
> - dev->post_rx_burst_cbs[queue_id];
> -
> + struct rte_eth_rxtx_callback *cb = dev->post_rx_burst_cbs[queue_id];
> + if (unlikely(cb != NULL)) {
> do {
> nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts, nb_rx,
> nb_pkts, cb->param);
To fix TOCTOU like this you need to use something like READ_ONCE()
which does cast to volatile.
For Developer Certificate of Origin (Signed-off-by) you must use a person
not a team. It is a legal requirement. If you don't know what DCO is you should
read what it means.
Developer's Certificate of Origin 1.1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or
(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.
(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
then you just add a line saying::
Signed-off-by: Random J Developer <ran...@developer.example.org>
using your real name (sorry, no pseudonyms or anonymous contributions.)
