Re: [PATCH v4] testpmd: cleanup cleanly from signal

["Mattias Rönnblom" <hofors@lysator.liu.se>]

On 2022-11-09 05:10, Stephen Hemminger wrote:
> Do a clean shutdown of testpmd when a signal is received;
> instead of having testpmd kill itself.
> This fixes problem where a signal could be received
> in the middle of a PMD and then the signal handler would call
> PMD's close routine which could cause a deadlock.
> 
> Added benefit is it gets rid of Windows specific code.
> 
> Fixes: d9a191a00e81 ("app/testpmd: fix quitting in container")
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
> v4 - use select() because that is available on Windows; and other
>       functions poll() and sigaction() are not.
> 
>   app/test-pmd/testpmd.c | 63 +++++++++++++++++++++++-------------------
>   1 file changed, 34 insertions(+), 29 deletions(-)
> 
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> index cf5942d0c422..274e96cac2d4 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -12,6 +12,7 @@
>   #ifndef RTE_EXEC_ENV_WINDOWS
>   #include <sys/mman.h>
>   #endif
> +#include <sys/select.h>
>   #include <sys/types.h>
>   #include <errno.h>
>   #include <stdbool.h>
> @@ -4251,26 +4252,11 @@ print_stats(void)
>   static void
>   signal_handler(int signum)
>   {
> -	if (signum == SIGINT || signum == SIGTERM) {
> -		fprintf(stderr, "\nSignal %d received, preparing to exit...\n",
> -			signum);
> -#ifdef RTE_LIB_PDUMP
> -		/* uninitialize packet capture framework */
> -		rte_pdump_uninit();
> -#endif
> -#ifdef RTE_LIB_LATENCYSTATS
> -		if (latencystats_enabled != 0)
> -			rte_latencystats_uninit();
> -#endif
> -		force_quit();
> -		/* Set flag to indicate the force termination. */
> -		f_quit = 1;
> -		/* exit with the expected status */
> -#ifndef RTE_EXEC_ENV_WINDOWS
> -		signal(signum, SIG_DFL);
> -		kill(getpid(), signum);
> -#endif
> -	}
> +	fprintf(stderr, "\nSignal %d %s received, preparing to exit...\n",
> +		signum, strsignal(signum));

fprintf() is not async signal safe, and neither is strsignal().

This is not a regression introduced by this patch, but I thought it 
might be worth fixing.

> +
> +	/* Set flag to indicate the force termination. */
> +	f_quit = 1;
>   }
>   
>   int
> @@ -4449,9 +4435,6 @@ main(int argc, char** argv)
>   	} else
>   #endif
>   	{
> -		char c;
> -		int rc;
> -
>   		f_quit = 0;
>   
>   		printf("No commandline core given, start packet forwarding\n");
> @@ -4476,15 +4459,37 @@ main(int argc, char** argv)
>   				prev_time = cur_time;
>   				rte_delay_us_sleep(US_PER_S);
>   			}
> -		}
> +		} else {
> +			char c;
> +			fd_set fds;
>   
> -		printf("Press enter to exit\n");
> -		rc = read(0, &c, 1);
> -		pmd_test_exit();
> -		if (rc < 0)
> -			return 1;
> +			printf("Press enter to exit\n");
> +
> +			FD_ZERO(&fds);
> +			FD_SET(0, &fds);
> +
> +			if (select(1, &fds, NULL, NULL, NULL) <= 0) {
> +				fprintf(stderr, "Select failed: %s\n",
> +					strerror(errno));

Why is select() needed? Wouldn't a blocking read suffice? Or getchar().

> +			} else if (read(0, &c, 1) <= 0) {
> +				fprintf(stderr,
> +					"Read stdin failed: %s\n",
> +					strerror(errno));
> +			}
> +		}
> +		stop_packet_forwarding();
> +		force_quit();
>   	}
>   
> +#ifdef RTE_LIB_PDUMP
> +	/* uninitialize packet capture framework */
> +	rte_pdump_uninit();
> +#endif
> +#ifdef RTE_LIB_LATENCYSTATS
> +	if (latencystats_enabled != 0)
> +		rte_latencystats_uninit();
> +#endif
> +
>   	ret = rte_eal_cleanup();
>   	if (ret != 0)
>   		rte_exit(EXIT_FAILURE,