[dm-devel] [PATCH 5/7] multipathd: set DAEMON_CONFIGURE from uxlsnr thread

[Benjamin Marzinski]

On Wed, Oct 24, 2018 at 12:05:50AM +0200, Martin Wilck wrote:
> Commit ee01e841 had the intention to make multipathd quit if
> the client socket couldn't be set up, because the unix socket
> listener is vital for signal handling in multipathd.
> But during startup, this condition might be lost if the main
> thread doesn't wait for the unix listener to initialize.
> 
> Fixes: ee01e841 "multipathd: handle errors in uxlsnr as fatal"
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  multipathd/main.c | 43 ++++++++++++++++++++++++++++++++-----------
>  1 file changed, 32 insertions(+), 11 deletions(-)
> 
> diff --git a/multipathd/main.c b/multipathd/main.c
> index 50f69171..c71e7d03 100644
> --- a/multipathd/main.c
> +++ b/multipathd/main.c
> @@ -205,9 +205,8 @@ static void config_cleanup(void *arg)
>  	pthread_mutex_unlock(&config_lock);
>  }
>  
> -void post_config_state(enum daemon_status state)
> +static void __post_config_state(enum daemon_status state)
>  {
> -	pthread_mutex_lock(&config_lock);
>  	if (state != running_state) {
>  		enum daemon_status old_state = running_state;
>  
> @@ -217,7 +216,14 @@ void post_config_state(enum daemon_status state)
>  		do_sd_notify(old_state);
>  #endif
>  	}
> -	pthread_mutex_unlock(&config_lock);
> +}
> +
> +void post_config_state(enum daemon_status state)
> +{
> +	pthread_mutex_lock(&config_lock);
> +	pthread_cleanup_push(config_cleanup, NULL);
> +	__post_config_state(state);
> +	pthread_cleanup_pop(1);
>  }
>  
>  int set_config_state(enum daemon_status state)
> @@ -1511,6 +1517,10 @@ uxlsnrloop (void * ap)
>  		condlog(1, "Failed to init uxsock listener");
>  		return NULL;
>  	}
> +
> +	/* Tell main thread that thread has started */
> +	post_config_state(DAEMON_CONFIGURE);
> +
>  	set_handler_callback(LIST+PATHS, cli_list_paths);
>  	set_handler_callback(LIST+PATHS+FMT, cli_list_paths_fmt);
>  	set_handler_callback(LIST+PATHS+RAW+FMT, cli_list_paths_raw);
> @@ -2726,11 +2736,26 @@ child (void * param)
>  	 */
>  	conf = NULL;
>  
> -	/*
> -	 * Signal start of configuration
> -	 */
> -	post_config_state(DAEMON_CONFIGURE);
> +	pthread_cleanup_push(config_cleanup, NULL);
> +	pthread_mutex_lock(&config_lock);
>  
> +	__post_config_state(DAEMON_IDLE);

I don't really understand the need for __post_config_state().  Couldn't
you just call post_config_state(DAEMON_IDLE), and then grab the
config_lock after checking that the thread was created successfully.  If
the scheduler decides to run the uxlsnrloop thread before continuing
with the child thread, it would be better if uxlsnrloop thread was free
to grab the config lock anyway.

At any rate, what you have is perfectly correct, so

Reviewed-by: Benjamin Marzinsk <bmarzins at redhat.com>

> +	rc = pthread_create(&uxlsnr_thr, &misc_attr, uxlsnrloop, vecs);
> +	if (!rc) {
> +		/* Wait for uxlsnr startup */
> +		while (running_state == DAEMON_IDLE)
> +			pthread_cond_wait(&config_cond, &config_lock);
> +	}
> +	pthread_cleanup_pop(1);
> +
> +	if (rc) {
> +		condlog(0, "failed to create cli listener: %d", rc);
> +		goto failed;
> +	}
> +	else if (running_state != DAEMON_CONFIGURE) {
> +		condlog(0, "cli listener failed to start");
> +		goto failed;
> +	}
>  
>  	if (poll_dmevents) {
>  		if (init_dmevent_waiter(vecs)) {
> @@ -2753,10 +2778,6 @@ child (void * param)
>  		goto failed;
>  	}
>  	pthread_attr_destroy(&uevent_attr);
> -	if ((rc = pthread_create(&uxlsnr_thr, &misc_attr, uxlsnrloop, vecs))) {
> -		condlog(0, "failed to create cli listener: %d", rc);
> -		goto failed;
> -	}
>  
>  	/*
>  	 * start threads
> -- 
> 2.19.1