Ping: [PATCH 1/1] Fix deadlock when running run_iter_bw_infinitely

[Hans Westgaard Ry <hans.westgaard.ry-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

Any comments on this patch ?



On 11/18/2015 01:27 PM, Hans Westgaard Ry wrote:
> The test uses a signal-handler to periodically print a line of report.
> Snip libc info:
> <quote>
> 24.4.6 Signal Handling and Nonreentrant Functions
> Handler functions usually don't do very much.  The best practice is to
> write a handler that does nothing but set an external variable that the
> program checks regularly, and leave all serious work to the program.
> </quote>
> The current codebase violates the above and is deadlock prone.
> The mutexes taken by the printf functions called from the signal handler
> might be held by activity conducted by the main thread.
>
> This commit fixes this by setting a flag in the signal handler and handle the
> printout in the mainloop of the test.
>
> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Reviewed-by: Håkon Bugge <haakon.bugge-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Reviewed-by: Knut Omang <knut.omang-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> ---
>   src/perftest_resources.c | 22 ++++++++++++++++------
>   1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/src/perftest_resources.c b/src/perftest_resources.c
> index cb915e0..4d8e6c0 100755
> --- a/src/perftest_resources.c
> +++ b/src/perftest_resources.c
> @@ -25,6 +25,12 @@ static enum ibv_wr_opcode opcode_atomic_array[] =IBV_WR_ATOMIC_CMP_AND_SWP,IBV
>   
>   struct perftest_parameters* duration_param;
>   struct check_alive_data check_alive_data;
> +/*
> + * Flag to trig call to print_report_bw
> + * The flag is set in signal_handler and tested/reset in run_iter_bw_infinitely
> + */
> +static volatile int trig_print_report_bw =;
> +
>   
>   /******************************************************************************
>    * Beginning
> @@ -3214,7 +3220,15 @@ int run_iter_bw_infinitely(struct pingpong_context *ctx,struct perftest_paramete
>   
>   	/* main loop for posting */
>   	while (1) {
> -
> +		if (trig_print_report_bw) {
> +			duration_param->tcompleted[0] =et_cycles();
> +			print_report_bw(duration_param,NULL);
> +			duration_param->iters =;
> +			alarm(duration_param->duration);
> +			duration_param->tposted[0] =et_cycles();
> +			trig_print_report_bw =;
> +		}
> +		
>   		/* main loop to run over all the qps and post each time n messages */
>   		for (index =; index < num_of_qps ; index++) {
>   
> @@ -4213,11 +4227,7 @@ void check_alive(int sig)
>    ******************************************************************************/
>   void catch_alarm_infintely(int sig)
>   {
> -	duration_param->tcompleted[0] =et_cycles();
> -	print_report_bw(duration_param,NULL);
> -	duration_param->iters =;
> -	alarm(duration_param->duration);
> -	duration_param->tposted[0] =et_cycles();
> +	trig_print_report_bw =;
>   }
>   
>   /******************************************************************************

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