Re: [dpdk-dev] [PATCHv5] eal: remove sys/queue.h from public headers.

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

2021-08-13 03:36 (UTC+0000), William Tu:
> Currently there are some public headers that include 'sys/queue.h', which
> is not POSIX, but usually provided by the Linux/BSD system library.
> (Not in POSIX.1, POSIX.1-2001, or POSIX.1-2008. Present on the BSDs.)
> The file is missing on Windows. During the windows build, DPDK uses a

Typo: "Windows".

> bundled copy, so building a DPDK library works fine.  But when OVS or other
> applications use DPDK as a library, because some DPDK public headers
> include 'sys/queue.h', on Windows, it triggers an error due to no such file.
> 
> One solution is to install the 'lib/eal/windows/include/sys/queue.h' into
> Windows environment, such as [1]. However, this means DPDK exports the
> functionalities of 'sys/queue.h' into the environment, which might cause
> symbols, macros, headers clashing with other applications.
> 
> The patch fixes it by removing the "#include <sys/queue.h>" from
> DPDK public headers, so programs including DPDK headers don't depend
> on the system to provide 'sys/queue.h'. When these public headers use
> macros such as TAILQ_xxx, we replace it with RTE_ prefix.

"replace it by _the ones_ with RTE_ prefix"?

> For Windows, we copy the definitions from <sys/queue.h> to rte_os.h
> under windows. Note that these RTE_ macros are compatible with

"under windows" -> "in Windows EAL"

> <sys/queue.h>, only at the level of API (to use with <sys/queue.h>

"only" -> "both"

> macros in C files) and ABI (to avoid breaking it).
> 
> Additionally, the TAILQ_FOREACH_SAFE is not part of <sys/queue.h>,
> the patch replaces it with RTE_TAILQ_FOREACH_SAFE.

> With this patch, all the public headers no longer have
> "#include <sys/queue.h>" or "TAILQ_xxx" macros.

This is a repetition of what is stated in the previous paragraph.

> 
> [1] http://mails.dpdk.org/archives/dev/2021-August/216304.html
> 
> Suggested-by: Nick Connolly <nick.connolly@mayadata.io>
> Suggested-by: Dmitry Kozliuk <Dmitry.Kozliuk@gmail.com>
> Signed-off-by: William Tu <u9012063@gmail.com>
> ---
> v4-v5
> * fix compile error due to drivers/net/ipn3ke/ipn3ke_flow.c:1234
> * run spell check

1. Please register at http://patchwork.dpdk.org with the email used for the
patches and update the state of all previous versions to "Superseded".
It is not currently done automatically and only you and a few maintainers
can change the state.

Patchwork also shows CI build failures with v5, they need to be fixed.

2. Are you using `git format-patch -v5 ...` to create patches?
The subject of your patches is missing a space ("PATCH v5" vs "PATCHv5").
Not sure if tools like patchwork will properly process it.

[...]
>  struct rte_afu_driver {
> -	TAILQ_ENTRY(rte_afu_driver) next;       /**< Next afu driver. */
> +	RTE_TAILQ_ENTRY(rte_afu_driver) next;       /**< Next afu driver. */
>  	struct rte_driver driver;               /**< Inherit core driver. */
>  	afu_probe_t *probe;                     /**< Device Probe function. */
>  	afu_remove_t *remove;                   /**< Device Remove function. */

Re: loss of comment alignment here and in other places.
Firstly, it's definitely not a big deal. Current patch is good because it only
changes relevant lines. Re-aligning all the comments would be worse IMO.
However, in cases like this, when keeping alignment doesn't require changing
neighboring lines, it could be kept. Just a nit.

[...]
>  /* This macro permits both remove and free var within the loop safely.*/
> -#ifndef TAILQ_FOREACH_SAFE
> -#define TAILQ_FOREACH_SAFE(var, head, field, tvar)		\
> -	for ((var) = TAILQ_FIRST((head));			\
> -	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);	\
> +#ifndef RTE_TAILQ_FOREACH_SAFE
> +#define RTE_TAILQ_FOREACH_SAFE(var, head, field, tvar)		\
> +	for ((var) = RTE_TAILQ_FIRST((head));			\
> +	    (var) && ((tvar) = RTE_TAILQ_NEXT((var), field), 1);	\
>  	    (var) = (tvar))
>  #endif

Why duplicate this in rte_os.h (documentation lost, BTW) and add #ifdef?
RTE_TAILQ_FOREACH_SAFE is not needed in headers, it can be left here.

>  
> diff --git a/lib/eal/linux/include/rte_os.h b/lib/eal/linux/include/rte_os.h
> index 1618b4df22..1a6e5b789f 100644
> --- a/lib/eal/linux/include/rte_os.h
> +++ b/lib/eal/linux/include/rte_os.h
> @@ -11,6 +11,21 @@
>   */
>  
>  #include <sched.h>
> +#include <sys/queue.h>
> +
> +/* These macros are compatible with system's sys/queue.h. */
> +#define RTE_TAILQ_HEAD(name, type) TAILQ_HEAD(name, type)
> +#define RTE_TAILQ_ENTRY(type) TAILQ_ENTRY(type)
> +#define RTE_TAILQ_FOREACH(var, head, field) TAILQ_FOREACH(var, head, field)
> +#define	RTE_TAILQ_FOREACH_SAFE(var, head, field, tvar) \

Stray TAB here and in rte_os.h for other platforms.