On Fri, Sep 10, 2021 at 01:40:52PM +0200, mwilck@xxxxxxxx wrote:
> From: Martin Wilck <mwilck@xxxxxxxx>
>
> When a reconfigure operation is requested, either by the admin
> or by some condition multipathd encounters, the current code
> attempts to set DAEMON_CONFIGURE state and gives up after a second
> if it doesn't succeed. Apart from shutdown, this happens only
> if multipathd is either already reconfiguring, or busy in the
> path checker loop.
>
> This patch modifies the logic as follows: rather than waiting,
> we set a flag that requests a reconfigure operation asap, i.e.
> when the current operation is finished and the status switched
> to DAEMON_IDLE. In this case, multipathd will not switch to IDLE
> but start another reconfigure cycle.
>
> This assumes that if a reconfigure is requested while one is already
> running, the admin has made some (additional) changes and wants
> multipathd to pull them in. As we can't be sure that the currently
> running reconfigure has seen the configuration changes, we need
> to start over again.
>
> A positive side effect is less waiting in clients and multipathd.
>
> After this change, the only caller of set_config_state() is
> checkerloop(). Waking up every second just to see that DAEMON_RUNNING
> couldn't be set makes no sense. Therefore set_config_state() is
> changed to wait "forever", or until shutdown is requested. Unless
> multipathd completely hangs, the wait will terminate sooner or
> later.
>
> Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
> ---
> multipathd/cli_handlers.c | 10 +----
> multipathd/main.c | 92 +++++++++++++++++++++++++++++----------
> multipathd/main.h | 3 +-
> 3 files changed, 71 insertions(+), 34 deletions(-)
>
> diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
> index 6d3a0ae..44f76ee 100644
> --- a/multipathd/cli_handlers.c
> +++ b/multipathd/cli_handlers.c
> @@ -1076,17 +1076,9 @@ cli_switch_group(void * v, char ** reply, int * len, void * data)
> int
> cli_reconfigure(void * v, char ** reply, int * len, void * data)
> {
> - int rc;
> -
> condlog(2, "reconfigure (operator)");
>
> - rc = set_config_state(DAEMON_CONFIGURE);
> - if (rc == ETIMEDOUT) {
> - condlog(2, "timeout starting reconfiguration");
> - return 1;
> - } else if (rc == EINVAL)
> - /* daemon shutting down */
> - return 1;
> + schedule_reconfigure();
> return 0;
> }
>
> diff --git a/multipathd/main.c b/multipathd/main.c
> index 67160b9..5fb6989 100644
> --- a/multipathd/main.c
> +++ b/multipathd/main.c
> @@ -221,6 +221,10 @@ static void do_sd_notify(enum daemon_status old_state,
> } else if (new_state == DAEMON_CONFIGURE && startup_done)
> sd_notify(0, "RELOADING=1");
> }
> +#else
> +static void do_sd_notify(__attribute__((unused)) enum daemon_status old_state,
> + __attribute__((unused)) enum daemon_status new_state)
> +{}
> #endif
>
> static void config_cleanup(__attribute__((unused)) void *arg)
> @@ -266,19 +270,38 @@ enum daemon_status wait_for_state_change_if(enum daemon_status oldstate,
> return st;
> }
>
> +/* Don't access this variable without holding config_lock */
> +static bool reconfigure_pending;
> +
> /* must be called with config_lock held */
> static void __post_config_state(enum daemon_status state)
> {
> if (state != running_state && running_state != DAEMON_SHUTDOWN) {
> -#ifdef USE_SYSTEMD
> enum daemon_status old_state = running_state;
> -#endif
>
> + /*
> + * Handle a pending reconfigure request.
> + * DAEMON_IDLE is set from child() after reconfigure(),
> + * or from checkerloop() after completing checkers.
> + * In either case, child() will see DAEMON_CONFIGURE
> + * again and start another reconfigure cycle.
> + */
> + if (reconfigure_pending && state == DAEMON_IDLE &&
> + (old_state == DAEMON_CONFIGURE ||
> + old_state == DAEMON_RUNNING)) {
> + /*
> + * notify systemd of transient idle state, lest systemd
> + * thinks the reload lasts forever.
> + */
> + do_sd_notify(old_state, DAEMON_IDLE);
> + old_state = DAEMON_IDLE;
> + state = DAEMON_CONFIGURE;
> + }
> + if (reconfigure_pending && state == DAEMON_CONFIGURE)
> + reconfigure_pending = false;
> running_state = state;
> pthread_cond_broadcast(&config_cond);
> -#ifdef USE_SYSTEMD
> do_sd_notify(old_state, state);
> -#endif
> }
> }
>
> @@ -290,24 +313,48 @@ void post_config_state(enum daemon_status state)
> pthread_cleanup_pop(1);
> }
>
> -int set_config_state(enum daemon_status state)
> +void schedule_reconfigure(void)
> +{
> + pthread_mutex_lock(&config_lock);
> + pthread_cleanup_push(config_cleanup, NULL);
> + switch (running_state)
> + {
> + case DAEMON_SHUTDOWN:
> + break;
> + case DAEMON_IDLE:
> + __post_config_state(DAEMON_CONFIGURE);
> + break;
> + case DAEMON_CONFIGURE:
> + case DAEMON_RUNNING:
> + reconfigure_pending = true;
> + break;
> + default:
> + break;
> + }
> + pthread_cleanup_pop(1);
> +}
> +
> +enum daemon_status set_config_state(enum daemon_status state)
> {
> int rc = 0;
> + enum daemon_status st;
>
> pthread_cleanup_push(config_cleanup, NULL);
> pthread_mutex_lock(&config_lock);
> - if (running_state != state) {
>
> - if (running_state == DAEMON_SHUTDOWN)
> - rc = EINVAL;
> - else
> - rc = __wait_for_state_change(
> - running_state != DAEMON_IDLE, 1000);
> - if (!rc)
> - __post_config_state(state);
> + while (rc == 0 &&
> + running_state != state &&
> + running_state != DAEMON_SHUTDOWN &&
> + running_state != DAEMON_IDLE) {
> + rc = pthread_cond_wait(&config_cond, &config_lock);
> }
> +
> + if (rc == 0 && running_state == DAEMON_IDLE && state != DAEMON_IDLE)
> + __post_config_state(state);
> + st = running_state;
> +
> pthread_cleanup_pop(1);
> - return rc;
> + return st;
> }
>
> struct config *get_multipath_config(void)
> @@ -734,7 +781,7 @@ ev_add_map (char * dev, const char * alias, struct vectors * vecs)
> if (delayed_reconfig &&
> !need_to_delay_reconfig(vecs)) {
> condlog(2, "reconfigure (delayed)");
> - set_config_state(DAEMON_CONFIGURE);
> + schedule_reconfigure();
> return 0;
> }
> }
> @@ -1845,7 +1892,7 @@ missing_uev_wait_tick(struct vectors *vecs)
> if (timed_out && delayed_reconfig &&
> !need_to_delay_reconfig(vecs)) {
> condlog(2, "reconfigure (delayed)");
> - set_config_state(DAEMON_CONFIGURE);
> + schedule_reconfigure();
> }
> }
>
> @@ -2484,6 +2531,10 @@ checkerloop (void *ap)
> int num_paths = 0, strict_timing, rc = 0;
> unsigned int ticks = 0;
>
> + if (set_config_state(DAEMON_RUNNING) != DAEMON_RUNNING)
> + /* daemon shutdown */
> + break;
> +
> get_monotonic_time(&start_time);
> if (start_time.tv_sec && last_time.tv_sec) {
> timespecsub(&start_time, &last_time, &diff_time);
> @@ -2499,13 +2550,6 @@ checkerloop (void *ap)
> if (use_watchdog)
> sd_notify(0, "WATCHDOG=1");
> #endif
> - rc = set_config_state(DAEMON_RUNNING);
> - if (rc == ETIMEDOUT) {
> - condlog(4, "timeout waiting for DAEMON_IDLE");
> - continue;
> - } else if (rc == EINVAL)
> - /* daemon shutdown */
> - break;
>
> pthread_cleanup_push(cleanup_lock, &vecs->lock);
> lock(&vecs->lock);
> @@ -2833,7 +2877,7 @@ handle_signals(bool nonfatal)
> return;
> if (reconfig_sig) {
> condlog(2, "reconfigure (signal)");
> - set_config_state(DAEMON_CONFIGURE);
> + schedule_reconfigure();
> }
> if (log_reset_sig) {
> condlog(2, "reset log (signal)");
> diff --git a/multipathd/main.h b/multipathd/main.h
> index bc1f938..23ce919 100644
> --- a/multipathd/main.h
> +++ b/multipathd/main.h
> @@ -37,6 +37,7 @@ void exit_daemon(void);
> const char * daemon_status(void);
> enum daemon_status wait_for_state_change_if(enum daemon_status oldstate,
> unsigned long ms);
> +void schedule_reconfigure(void);
> int need_to_delay_reconfig (struct vectors *);
> int reconfigure (struct vectors *);
> int ev_add_path (struct path *, struct vectors *, int);
> @@ -44,7 +45,7 @@ int ev_remove_path (struct path *, struct vectors *, int);
> int ev_add_map (char *, const char *, struct vectors *);
> int ev_remove_map (char *, char *, int, struct vectors *);
> int flush_map(struct multipath *, struct vectors *, int);
> -int set_config_state(enum daemon_status);
> +enum daemon_status set_config_state(enum daemon_status);
Can't we just remove set_config_state from main.h, and make it static?
Other than that, everything looks fine.
-Ben
> void * mpath_alloc_prin_response(int prin_sa);
> int prin_do_scsi_ioctl(char *, int rq_servact, struct prin_resp * resp,
> int noisy);
> --
> 2.33.0
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