Re: [dpdk-dev] [PATCH] eal: fix use wrong time API

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

> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Min Hu (Connor)
> Sent: Wednesday, April 28, 2021 10:13 AM
> 
> From: Chengwen Feng <fengchengwen@huawei.com>
> 
> Currently, the mp uses gettimeofday() API to get the time, and used as
> timeout parameter.
> 
> But the time which gets from gettimeofday() API isn't monotonically
> increasing. The process may fail if the system time is changed.
> 
> This fixes it by using clock_gettime() API with monotonic attribution.
> 
> Fixes: 783b6e54971d ("eal: add synchronous multi-process
> communication")
> Fixes: f05e26051c15 ("eal: add IPC asynchronous request")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
> ---
>  lib/eal/common/eal_common_proc.c | 45 +++++++++++++++++---------------
> --------
>  1 file changed, 19 insertions(+), 26 deletions(-)
> 
> diff --git a/lib/eal/common/eal_common_proc.c
> b/lib/eal/common/eal_common_proc.c
> index 6d1af3c..7f08826 100644
> --- a/lib/eal/common/eal_common_proc.c
> +++ b/lib/eal/common/eal_common_proc.c
> @@ -40,6 +40,12 @@ static char mp_dir_path[PATH_MAX]; /* The directory
> path for all mp sockets */
>  static pthread_mutex_t mp_mutex_action = PTHREAD_MUTEX_INITIALIZER;
>  static char peer_name[PATH_MAX];
> 
> +#ifdef CLOCK_MONOTONIC_RAW /* Defined in glibc bits/time.h */
> +#define CLOCK_TYPE_ID CLOCK_MONOTONIC_RAW
> +#else
> +#define CLOCK_TYPE_ID CLOCK_MONOTONIC
> +#endif

Just out of curiosity: Why do you prefer CLOCK_MONOTONIC_RAW over CLOCK_MONOTONIC?

> +
>  struct action_entry {
>  	TAILQ_ENTRY(action_entry) next;
>  	char action_name[RTE_MP_MAX_NAME_LEN];
> @@ -490,14 +496,8 @@ async_reply_handle_thread_unsafe(void *arg)
>  	struct pending_request *req = (struct pending_request *)arg;
>  	enum async_action action;
>  	struct timespec ts_now;
> -	struct timeval now;
> 
> -	if (gettimeofday(&now, NULL) < 0) {
> -		RTE_LOG(ERR, EAL, "Cannot get current time\n");
> -		goto no_trigger;
> -	}
> -	ts_now.tv_nsec = now.tv_usec * 1000;
> -	ts_now.tv_sec = now.tv_sec;
> +	clock_gettime(CLOCK_TYPE_ID, &ts_now);
> 
>  	action = process_async_request(req, &ts_now);
> 
> @@ -896,6 +896,7 @@ mp_request_sync(const char *dst, struct rte_mp_msg
> *req,
>  	       struct rte_mp_reply *reply, const struct timespec *ts)
>  {
>  	int ret;
> +	pthread_condattr_t attr;
>  	struct rte_mp_msg msg, *tmp;
>  	struct pending_request pending_req, *exist;
> 
> @@ -904,7 +905,9 @@ mp_request_sync(const char *dst, struct rte_mp_msg
> *req,
>  	strlcpy(pending_req.dst, dst, sizeof(pending_req.dst));
>  	pending_req.request = req;
>  	pending_req.reply = &msg;
> -	pthread_cond_init(&pending_req.sync.cond, NULL);
> +	pthread_condattr_init(&attr);
> +	pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);

Shouldn't CLOCK_MONOTONIC be CLOCK_TYPE_ID here too?

> +	pthread_cond_init(&pending_req.sync.cond, &attr);
> 
>  	exist = find_pending_request(dst, req->name);
>  	if (exist) {
> @@ -967,8 +970,7 @@ rte_mp_request_sync(struct rte_mp_msg *req, struct
> rte_mp_reply *reply,
>  	int dir_fd, ret = -1;
>  	DIR *mp_dir;
>  	struct dirent *ent;
> -	struct timeval now;
> -	struct timespec end;
> +	struct timespec now, end;
>  	const struct internal_config *internal_conf =
>  		eal_get_internal_configuration();
> 
> @@ -987,15 +989,10 @@ rte_mp_request_sync(struct rte_mp_msg *req,
> struct rte_mp_reply *reply,
>  		return -1;
>  	}
> 
> -	if (gettimeofday(&now, NULL) < 0) {
> -		RTE_LOG(ERR, EAL, "Failed to get current time\n");
> -		rte_errno = errno;
> -		goto end;
> -	}
> -
> -	end.tv_nsec = (now.tv_usec * 1000 + ts->tv_nsec) % 1000000000;
> +	clock_gettime(CLOCK_TYPE_ID, &now);
> +	end.tv_nsec = (now.tv_nsec + ts->tv_nsec) % 1000000000;
>  	end.tv_sec = now.tv_sec + ts->tv_sec +
> -			(now.tv_usec * 1000 + ts->tv_nsec) / 1000000000;
> +			(now.tv_nsec + ts->tv_nsec) / 1000000000;
> 
>  	/* for secondary process, send request to the primary process
> only */
>  	if (rte_eal_process_type() == RTE_PROC_SECONDARY) {
> @@ -1069,7 +1066,7 @@ rte_mp_request_async(struct rte_mp_msg *req,
> const struct timespec *ts,
>  	int dir_fd, ret = 0;
>  	DIR *mp_dir;
>  	struct dirent *ent;
> -	struct timeval now;
> +	struct timespec now;
>  	struct timespec *end;
>  	bool dummy_used = false;
>  	const struct internal_config *internal_conf =
> @@ -1086,11 +1083,6 @@ rte_mp_request_async(struct rte_mp_msg *req,
> const struct timespec *ts,
>  		return -1;
>  	}
> 
> -	if (gettimeofday(&now, NULL) < 0) {
> -		RTE_LOG(ERR, EAL, "Failed to get current time\n");
> -		rte_errno = errno;
> -		return -1;
> -	}
>  	copy = calloc(1, sizeof(*copy));
>  	dummy = calloc(1, sizeof(*dummy));
>  	param = calloc(1, sizeof(*param));
> @@ -1108,9 +1100,10 @@ rte_mp_request_async(struct rte_mp_msg *req,
> const struct timespec *ts,
>  	end = &param->end;
>  	reply = &param->user_reply;
> 
> -	end->tv_nsec = (now.tv_usec * 1000 + ts->tv_nsec) % 1000000000;
> +	clock_gettime(CLOCK_TYPE_ID, &now);
> +	end->tv_nsec = (now.tv_nsec + ts->tv_nsec) % 1000000000;
>  	end->tv_sec = now.tv_sec + ts->tv_sec +
> -			(now.tv_usec * 1000 + ts->tv_nsec) / 1000000000;
> +			(now.tv_nsec + ts->tv_nsec) / 1000000000;
>  	reply->nb_sent = 0;
>  	reply->nb_received = 0;
>  	reply->msgs = NULL;
> --
> 2.7.4
>