I noticed that the io_error checker thread accounts for most of the
activity of multipathd even if the marginal path checking paramters
are not set (which is still the default in most installations I assume).

Therefore, start the io_error checker thread only if there's at least
one map with marginal error path checking configured. Also, make sure
the thread is really up when start_io_err_stat_thread() returns.

This requires adding a "vecs" argument to setup_map, because vecs
needs to be passed to the io_error checking code.

Signed-off-by: Martin Wilck <mwi...@suse.com>
---
 libmultipath/configure.c   | 14 ++++++++---
 libmultipath/configure.h   |  3 ++-
 libmultipath/io_err_stat.c | 58 ++++++++++++++++++++++++++++++++++++++++++----
 libmultipath/structs_vec.c |  3 ++-
 multipathd/cli_handlers.c  |  2 +-
 multipathd/main.c          |  8 ++-----
 6 files changed, 72 insertions(+), 16 deletions(-)

diff --git a/libmultipath/configure.c b/libmultipath/configure.c
index 42b7c896ee65..fa6e21cb31af 100644
--- a/libmultipath/configure.c
+++ b/libmultipath/configure.c
@@ -41,6 +41,7 @@
 #include "uxsock.h"
 #include "wwids.h"
 #include "sysfs.h"
+#include "io_err_stat.h"
 
 /* group paths in pg by host adapter
  */
@@ -255,7 +256,8 @@ int rr_optimize_path_order(struct pathgroup *pgp)
        return 0;
 }
 
-int setup_map(struct multipath *mpp, char *params, int params_size)
+int setup_map(struct multipath *mpp, char *params, int params_size,
+             struct vectors *vecs)
 {
        struct pathgroup * pgp;
        struct config *conf;
@@ -315,6 +317,12 @@ int setup_map(struct multipath *mpp, char *params, int 
params_size)
 
        sysfs_set_scsi_tmo(mpp, conf->checkint);
        put_multipath_config(conf);
+
+       if (mpp->marginal_path_double_failed_time > 0 &&
+           mpp->marginal_path_err_sample_time > 0 &&
+           mpp->marginal_path_err_recheck_gap_time > 0 &&
+           mpp->marginal_path_err_rate_threshold >= 0)
+               start_io_err_stat_thread(vecs);
        /*
         * assign paths to path groups -- start with no groups and all paths
         * in mpp->paths
@@ -1019,7 +1027,7 @@ int coalesce_paths (struct vectors * vecs, vector newmp, 
char * refwwid,
                verify_paths(mpp, vecs);
 
                params[0] = '\0';
-               if (setup_map(mpp, params, PARAMS_SIZE)) {
+               if (setup_map(mpp, params, PARAMS_SIZE, vecs)) {
                        remove_map(mpp, vecs, 0);
                        continue;
                }
@@ -1348,7 +1356,7 @@ int reload_map(struct vectors *vecs, struct multipath 
*mpp, int refresh,
                        }
                }
        }
-       if (setup_map(mpp, params, PARAMS_SIZE)) {
+       if (setup_map(mpp, params, PARAMS_SIZE, vecs)) {
                condlog(0, "%s: failed to setup map", mpp->alias);
                return 1;
        }
diff --git a/libmultipath/configure.h b/libmultipath/configure.h
index 0f5d30a540ca..27a7e6f60a63 100644
--- a/libmultipath/configure.h
+++ b/libmultipath/configure.h
@@ -28,7 +28,8 @@ enum actions {
 
 struct vectors;
 
-int setup_map (struct multipath * mpp, char * params, int params_size );
+int setup_map (struct multipath * mpp, char * params, int params_size,
+              struct vectors *vecs );
 int domap (struct multipath * mpp, char * params, int is_daemon);
 int reinstate_paths (struct multipath *mpp);
 int coalesce_paths (struct vectors *vecs, vector curmp, char * refwwid, int 
force_reload, enum mpath_cmds cmd);
diff --git a/libmultipath/io_err_stat.c b/libmultipath/io_err_stat.c
index 536ba87968fd..02b1453ea527 100644
--- a/libmultipath/io_err_stat.c
+++ b/libmultipath/io_err_stat.c
@@ -74,6 +74,10 @@ struct io_err_stat_path {
 pthread_t              io_err_stat_thr;
 pthread_attr_t         io_err_stat_attr;
 
+static pthread_mutex_t io_err_thread_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t io_err_thread_cond = PTHREAD_COND_INITIALIZER;
+static int io_err_thread_running = 0;
+
 static struct io_err_stat_pathvec *paths;
 struct vectors *vecs;
 io_context_t   ioctx;
@@ -316,6 +320,9 @@ int io_err_stat_handle_pathfail(struct path *path)
        struct timespec curr_time;
        int res;
 
+       if (uatomic_read(&io_err_thread_running) == 0)
+               return 1;
+
        if (path->io_err_disable_reinstate) {
                io_err_stat_log(3, "%s: reinstate is already disabled",
                                path->dev);
@@ -380,6 +387,8 @@ int hit_io_err_recheck_time(struct path *pp)
        struct timespec curr_time;
        int r;
 
+       if (uatomic_read(&io_err_thread_running) == 0)
+               return 0;
        if (pp->mpp->nr_active <= 0) {
                io_err_stat_log(2, "%s: recover path early", pp->dev);
                goto recover;
@@ -690,6 +699,16 @@ static void service_paths(void)
        pthread_mutex_unlock(&paths->mutex);
 }
 
+static void cleanup_unlock(void *arg)
+{
+       pthread_mutex_unlock((pthread_mutex_t*) arg);
+}
+
+static void cleanup_exited(void *arg)
+{
+       uatomic_set(&io_err_thread_running, 0);
+}
+
 static void *io_err_stat_loop(void *data)
 {
        sigset_t set;
@@ -698,10 +717,18 @@ static void *io_err_stat_loop(void *data)
        pthread_cleanup_push(rcu_unregister, NULL);
        rcu_register_thread();
 
+       pthread_cleanup_push(cleanup_exited, NULL);
+
        sigfillset(&set);
        sigdelset(&set, SIGUSR2);
 
        mlockall(MCL_CURRENT | MCL_FUTURE);
+
+       pthread_mutex_lock(&io_err_thread_lock);
+       uatomic_set(&io_err_thread_running, 1);
+       pthread_cond_broadcast(&io_err_thread_cond);
+       pthread_mutex_unlock(&io_err_thread_lock);
+
        while (1) {
                struct timespec ts;
 
@@ -716,12 +743,18 @@ static void *io_err_stat_loop(void *data)
                pselect(1, NULL, NULL, NULL, &ts, &set);
        }
 
+       pthread_cleanup_pop(1);
        pthread_cleanup_pop(1);
        return NULL;
 }
 
 int start_io_err_stat_thread(void *data)
 {
+       int ret;
+
+       if (uatomic_read(&io_err_thread_running) == 1)
+               return 0;
+
        if (io_setup(CONCUR_NR_EVENT, &ioctx) != 0) {
                io_err_stat_log(4, "io_setup failed");
                return 1;
@@ -730,12 +763,24 @@ int start_io_err_stat_thread(void *data)
        if (!paths)
                goto destroy_ctx;
 
-       if (pthread_create(&io_err_stat_thr, &io_err_stat_attr,
-                               io_err_stat_loop, data)) {
+       pthread_mutex_lock(&io_err_thread_lock);
+       pthread_cleanup_push(cleanup_unlock, &io_err_thread_lock);
+
+       ret = pthread_create(&io_err_stat_thr, &io_err_stat_attr,
+                            io_err_stat_loop, data);
+
+       while (!ret && !uatomic_read(&io_err_thread_running) &&
+              pthread_cond_wait(&io_err_thread_cond,
+                                &io_err_thread_lock) == 0);
+
+       pthread_cleanup_pop(1);
+
+       if (ret) {
                io_err_stat_log(0, "cannot create io_error statistic thread");
                goto out_free;
        }
-       io_err_stat_log(3, "thread started");
+
+       io_err_stat_log(2, "io_error statistic thread started");
        return 0;
 
 out_free:
@@ -748,7 +793,12 @@ destroy_ctx:
 
 void stop_io_err_stat_thread(void)
 {
-       pthread_cancel(io_err_stat_thr);
+       if (io_err_stat_thr == (pthread_t)0)
+               return;
+
+       if (uatomic_read(&io_err_thread_running) == 1)
+               pthread_cancel(io_err_stat_thr);
+
        pthread_join(io_err_stat_thr, NULL);
        free_io_err_pathvec(paths);
        io_destroy(ioctx);
diff --git a/libmultipath/structs_vec.c b/libmultipath/structs_vec.c
index 3aafee7b217b..b3b94678438a 100644
--- a/libmultipath/structs_vec.c
+++ b/libmultipath/structs_vec.c
@@ -18,6 +18,7 @@
 #include "prio.h"
 #include "configure.h"
 #include "libdevmapper.h"
+#include "io_err_stat.h"
 
 /*
  * creates or updates mpp->paths reading mpp->pg
@@ -426,7 +427,7 @@ retry:
        mpp->action = ACT_RELOAD;
 
        extract_hwe_from_path(mpp);
-       if (setup_map(mpp, params, PARAMS_SIZE)) {
+       if (setup_map(mpp, params, PARAMS_SIZE, vecs)) {
                condlog(0, "%s: failed to setup new map in update", mpp->alias);
                retries = -1;
                goto fail;
diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
index c0ae54aae841..7169e8d3d7ed 100644
--- a/multipathd/cli_handlers.c
+++ b/multipathd/cli_handlers.c
@@ -894,7 +894,7 @@ int resize_map(struct multipath *mpp, unsigned long long 
size,
 
        mpp->size = size;
        update_mpp_paths(mpp, vecs->pathvec);
-       setup_map(mpp, params, PARAMS_SIZE);
+       setup_map(mpp, params, PARAMS_SIZE, vecs);
        mpp->action = ACT_RESIZE;
        mpp->force_udev_reload = 1;
        if (domap(mpp, params, 1) <= 0) {
diff --git a/multipathd/main.c b/multipathd/main.c
index 09a59292245f..ccfc41a1f680 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -734,7 +734,7 @@ rescan:
        /*
         * push the map to the device-mapper
         */
-       if (setup_map(mpp, params, PARAMS_SIZE)) {
+       if (setup_map(mpp, params, PARAMS_SIZE, vecs)) {
                condlog(0, "%s: failed to setup map for addition of new "
                        "path %s", mpp->alias, pp->dev);
                goto fail_map;
@@ -873,7 +873,7 @@ ev_remove_path (struct path *pp, struct vectors * vecs, int 
need_do_map)
                         */
                }
 
-               if (setup_map(mpp, params, PARAMS_SIZE)) {
+               if (setup_map(mpp, params, PARAMS_SIZE, vecs)) {
                        condlog(0, "%s: failed to setup map for"
                                " removal of path %s", mpp->alias, pp->dev);
                        goto fail;
@@ -2489,10 +2489,6 @@ child (void * param)
        /*
         * start threads
         */
-       rc = start_io_err_stat_thread(vecs);
-       if (rc)
-               goto failed;
-
        if ((rc = pthread_create(&check_thr, &misc_attr, checkerloop, vecs))) {
                condlog(0,"failed to create checker loop thread: %d", rc);
                goto failed;
-- 
2.16.1

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