Re: [dpdk-dev] spinlock: Move constructor function out of header file

[Jan Viktorin <viktorin@rehivetech.com>]

Hello Damjan,

thank you for the patch. It makes sense to me.

Next time, please CC the appropriate maintainers.
(See the MAINTAINERS file in the root of the DPDK source tree.)

In the subject after "spinlock:" you should start with a lower case
letter, so "move constructor..."

On Thu, 14 Jul 2016 15:27:29 +0200
damarion@cisco.com wrote:

> From: Damjan Marion <damarion@cisco.com>
> 
> Having constructor function in the header gile is generaly

I'd write:

Having constructor functions in header files is generally a bad idea.

Anyway:

s/gile/file/

> bad idea, as it will eventually be implanted to 3rd party
> library.
> 
> In this case it is causing linking issues with 3rd party

it causes linking issues

> libraries when application is not linked to dpdk, due to missing

an application

to dpdk due to a missing gymbol (no comma)

> symbol called by constructor.

Please include the following line:

Fixes: ba7468997ea6 ("spinlock: add HTM lock elision for x86")

> 
> Signed-off-by: Damjan Marion <damarion@cisco.com>
> 
> ---
> lib/librte_eal/common/arch/x86/rte_spinlock.c      | 45 ++++++++++++++++++++++
>  .../common/include/arch/x86/rte_spinlock.h         | 13 ++-----
>  lib/librte_eal/linuxapp/eal/Makefile               |  1 +
>  3 files changed, 49 insertions(+), 10 deletions(-)
>  create mode 100644 lib/librte_eal/common/arch/x86/rte_spinlock.c
> 
> diff --git a/lib/librte_eal/common/arch/x86/rte_spinlock.c b/lib/librte_eal/common/arch/x86/rte_spinlock.c
> new file mode 100644
> index 0000000..ad8cc5a
> --- /dev/null
> +++ b/lib/librte_eal/common/arch/x86/rte_spinlock.c
> @@ -0,0 +1,45 @@
> +/*-
> + *   BSD LICENSE
> + *
> + *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
> + *   All rights reserved.
> + *
> + *   Redistribution and use in source and binary forms, with or without
> + *   modification, are permitted provided that the following conditions
> + *   are met:
> + *
> + *     * Redistributions of source code must retain the above copyright
> + *       notice, this list of conditions and the following disclaimer.
> + *     * Redistributions in binary form must reproduce the above copyright
> + *       notice, this list of conditions and the following disclaimer in
> + *       the documentation and/or other materials provided with the
> + *       distribution.
> + *     * Neither the name of Intel Corporation nor the names of its
> + *       contributors may be used to endorse or promote products derived
> + *       from this software without specific prior written permission.
> + *
> + *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> + *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> + *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
> + *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> + *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> + *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> + *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> + *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
> + *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
> + */
> +
> +#include "rte_cpuflags.h"
> +
> +#include <stdint.h>

According to:
http://dpdk.org/doc/guides-16.04/contributing/coding_style.html#coding-style

you should change the order of these includes.

> +
> +uint8_t rte_rtm_supported; /* cache the flag to avoid the overhead
> +			      of the rte_cpu_get_flag_enabled function */

The comment should be placed before the declaration or use the /**< */
Doxygen style. I'd prefer to placed it before. Can you fix it with this
patch?

> +
> +static void __attribute__((constructor))
> +rte_rtm_init(void)
> +{
> +	rte_rtm_supported = rte_cpu_get_flag_enabled(RTE_CPUFLAG_RTM);
> +}
> diff --git a/lib/librte_eal/common/include/arch/x86/rte_spinlock.h b/lib/librte_eal/common/include/arch/x86/rte_spinlock.h
> index 02f95cb..8e630c2 100644
> --- a/lib/librte_eal/common/include/arch/x86/rte_spinlock.h
> +++ b/lib/librte_eal/common/include/arch/x86/rte_spinlock.h
> @@ -94,24 +94,17 @@ rte_spinlock_trylock (rte_spinlock_t *sl)
>  }
>  #endif
>  
> -static uint8_t rtm_supported; /* cache the flag to avoid the overhead
> -				 of the rte_cpu_get_flag_enabled function */
> -
> -static inline void __attribute__((constructor))
> -rte_rtm_init(void)
> -{
> -	rtm_supported = rte_cpu_get_flag_enabled(RTE_CPUFLAG_RTM);
> -}
> +extern uint8_t rte_rtm_supported;
>  
>  static inline int rte_tm_supported(void)
>  {
> -	return rtm_supported;
> +	return rte_rtm_supported;
>  }
>  
>  static inline int
>  rte_try_tm(volatile int *lock)
>  {
> -	if (!rtm_supported)
> +	if (!rte_rtm_supported)
>  		return 0;
>  
>  	int retries = RTE_RTM_MAX_RETRIES;
> diff --git a/lib/librte_eal/linuxapp/eal/Makefile b/lib/librte_eal/linuxapp/eal/Makefile
> index 1a97693..7287d13 100644
> --- a/lib/librte_eal/linuxapp/eal/Makefile
> +++ b/lib/librte_eal/linuxapp/eal/Makefile
> @@ -106,6 +106,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_keepalive.c
>  
>  # from arch dir
>  SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_cpuflags.c
> +SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_spinlock.c

This is not good, you provide rte_spinlock.c only for x86. Building
for any other arch would fail to find this file.
  
Moreover, the bsdapp/eal/Makefile should reflect this situation as
well.

Regards
Jan

>  
>  CFLAGS_eal_common_cpuflags.o := $(CPUFLAGS_LIST)
>