RE: [PATCH v3 2/3] eal: fix unckeck pipe

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Dengdui Huang [mailto:huangdengdui@huawei.com]
> Sent: Wednesday, 2 April 2025 14.25
> 
> The communication pipe may be unavailable, for example,
> when the lcore role is ROLE_OFF or ROLE_NON_EAL.
> So check whether the pipe is available before using it.
> 
> Fixes: a95d70547c57 ("eal: factorize lcore main loop")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dengdui Huang <huangdengdui@huawei.com>
> ---
>  lib/eal/unix/eal_unix_thread.c | 3 +++
>  lib/eal/windows/eal_thread.c   | 3 +++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/lib/eal/unix/eal_unix_thread.c
> b/lib/eal/unix/eal_unix_thread.c
> index ef6cbff0ee..103571cabf 100644
> --- a/lib/eal/unix/eal_unix_thread.c
> +++ b/lib/eal/unix/eal_unix_thread.c
> @@ -17,6 +17,9 @@ eal_thread_wake_worker(unsigned int worker_id)
>  	char c = 0;
>  	int n;
> 
> +	if (m2w == 0 || w2m == 0)
> +		return -EINVAL;
> +
>  	do {
>  		n = write(m2w, &c, 1);
>  	} while (n == 0 || (n < 0 && errno == EINTR));
> diff --git a/lib/eal/windows/eal_thread.c
> b/lib/eal/windows/eal_thread.c
> index 9e3df200b9..82bb974868 100644
> --- a/lib/eal/windows/eal_thread.c
> +++ b/lib/eal/windows/eal_thread.c
> @@ -24,6 +24,9 @@ eal_thread_wake_worker(unsigned int worker_id)
>  	char c = 0;
>  	int n;
> 
> +	if (m2w == 0 || w2m == 0)
> +		return -EINVAL;
> +
>  	do {
>  		n = _write(m2w, &c, 1);
>  	} while (n == 0 || (n < 0 && errno == EINTR));
> --
> 2.33.0

This internal function eal_thread_wake_worker() is only called from rte_eal_remote_launch().
It would be better to check the lcore role there.

References:
https://elixir.bootlin.com/dpdk/v25.03-rc2/A/ident/eal_thread_wake_worker
https://elixir.bootlin.com/dpdk/v25.03-rc2/source/lib/eal/common/eal_common_launch.c#L52

Furthermore, in theory, file descriptor 0 is a valid file descriptor; if "stdin" has been closed, a newly opened file (or pipe) may be assigned file descriptor 0.