Re: [PATCH v2] doc/eal: add signal safety warning

[Thomas Monjalon <thomas@monjalon.net>]

05/07/2022 22:44, Stephen Hemminger:
> The DPDK is not designed to be used from a signal handler.
> Add a notice in the documentation describing this limitation,
> similar to Linux signal-safety manual page.
> 
> Bugzilla ID: 1030
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> Acked-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  doc/guides/prog_guide/env_abstraction_layer.rst | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> index 67842ae27207..de7ee92bba39 100644
> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> @@ -818,6 +818,21 @@ Known Issues
>  
>    The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
>  
> ++ signal safety
> +
> +  The DPDK library is not designed to be async-signal-safe.
> +  Except where explicitly stated otherwise [#]_, the DPDK functions are nonreentrant and are unsafe to call from a signal handler.
> +
> +.. [#] Only the function ``rte_dump_stack()`` can safely be called from signal handler in this version of DPDK.

Really? Are you sure?

Note: the use of [#] is probably limited to a single usage in the page?

> +
> +.. note::
> +  The kinds of issues that make DPDK functions unsafe can be understood when
> +  one considers that much of the code in DPDK uses locks and other shared
> +  resources. If a device driver holding a ``rte_spinlock`` is interrupted
> +  by a signal and control operation is then performed that would acquire
> +  the same lock, a deadlock would result.

I find this note quite confusing.