Re: [PATCH v3 3/5] eal: set name when creating a control thread

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

Hi Olivier,

After this patch, I find the two IPC threads block at 
pthread_barrier_wait(), and never wake up. Please refer below for more 
information. The system is Ubuntu 16.04.

On 4/24/2018 10:46 PM, Olivier Matz wrote:
> To avoid code duplication, add a parameter to rte_ctrl_thread_create()
> to specify the name of the thread.
>
> This requires to add a wrapper for the thread start routine in
> rte_thread_init(), which will first wait that the thread is configured.
>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
>   drivers/net/kni/rte_eth_kni.c                |  3 +-
>   lib/librte_eal/common/eal_common_proc.c      | 15 +++-----
>   lib/librte_eal/common/eal_common_thread.c    | 52 +++++++++++++++++++++++++---
>   lib/librte_eal/common/include/rte_lcore.h    |  7 ++--
>   lib/librte_eal/linuxapp/eal/eal_interrupts.c | 13 ++-----
>   lib/librte_eal/linuxapp/eal/eal_timer.c      | 12 +------
>   lib/librte_vhost/socket.c                    | 25 +++----------
>   7 files changed, 66 insertions(+), 61 deletions(-)
[...]
> diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
> index efbccddbc..94d2a6e42 100644
> --- a/lib/librte_eal/common/eal_common_thread.c
> +++ b/lib/librte_eal/common/eal_common_thread.c
> @@ -7,6 +7,7 @@
>   #include <stdint.h>
>   #include <unistd.h>
>   #include <pthread.h>
> +#include <signal.h>
>   #include <sched.h>
>   #include <assert.h>
>   #include <string.h>
> @@ -141,10 +142,53 @@ eal_thread_dump_affinity(char *str, unsigned size)
>   	return ret;
>   }
>   
> +
> +struct rte_thread_ctrl_params {
> +	void *(*start_routine)(void *);
> +	void *arg;
> +	pthread_barrier_t configured;
> +};
> +
> +static void *rte_thread_init(void *arg)
> +{
> +	struct rte_thread_ctrl_params *params = arg;
> +	void *(*start_routine)(void *) = params->start_routine;
> +	void *routine_arg = params->arg;
> +
> +	pthread_barrier_wait(&params->configured);

This thread never wakes up. The call trace as below:

#0  0x00007ffff72a8154 in futex_wait (private=0, expected=0, 
futex_word=0x7fffffffcff4)
     at ../sysdeps/unix/sysv/linux/futex-internal.h:61
#1  futex_wait_simple (private=0, expected=0, futex_word=0x7fffffffcff4) 
at ../sysdeps/nptl/futex-internal.h:135
#2  __pthread_barrier_wait (barrier=0x7fffffffcff0) at 
pthread_barrier_wait.c:184
#3  0x000000000055216a in rte_thread_init (arg=0x7fffffffcfe0) at 
/home/tan/git/dpdk/lib/librte_eal/common/eal_common_thread.c:160
#4  0x00007ffff72a16ba in start_thread (arg=0x7ffff6ecf700) at 
pthread_create.c:333
#5  0x00007ffff6fd741d in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:109

> +
> +	return start_routine(routine_arg);
> +}
> +
>   __rte_experimental int
> -rte_ctrl_thread_create(pthread_t *thread,
> -			const pthread_attr_t *attr,
> -			void *(*start_routine)(void *), void *arg)
> +rte_ctrl_thread_create(pthread_t *thread, const char *name,
> +		const pthread_attr_t *attr,
> +		void *(*start_routine)(void *), void *arg)
>   {
> -	return pthread_create(thread, attr, start_routine, arg);
> +	struct rte_thread_ctrl_params params = {
> +		.start_routine = start_routine,
> +		.arg = arg,
> +	};
> +	int ret;
> +
> +	pthread_barrier_init(&params.configured, NULL, 2);
> +
> +	ret = pthread_create(thread, attr, rte_thread_init, (void *)&params);
> +	if (ret != 0)
> +		return ret;
> +
> +	if (name != NULL) {
> +		ret = rte_thread_setname(*thread, name);
> +		if (ret < 0)
> +			goto fail;
> +	}
> +
> +	pthread_barrier_wait(&params.configured);

Here, the thread wakes up normally, and continues.

Any idea on what's going on?

Thanks,
Jianfeng

> +
> +	return 0;
> +
> +fail:
> +	pthread_cancel(*thread);
> +	pthread_join(*thread, NULL);
> +	return ret;
>   }