diff --git a/block/blkdebug.c b/block/blkdebug.c
index dffd869b32..cf8b088ce7 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -54,6 +54,7 @@ typedef struct BDRVBlkdebugState {
     /* For blkdebug_refresh_filename() */
     char *config_file;
 
+    QemuMutex lock;
     QLIST_HEAD(, BlkdebugRule) rules[BLKDBG__MAX];
     QSIMPLEQ_HEAD(, BlkdebugRule) active_rules;
     QLIST_HEAD(, BlkdebugSuspendedReq) suspended_reqs;
@@ -245,7 +246,9 @@ static int add_rule(void *opaque, QemuOpts *opts, Error **errp)
     };
 
     /* Add the rule */
+    qemu_mutex_lock(&s->lock);
     QLIST_INSERT_HEAD(&s->rules[event], rule, next);
+    qemu_mutex_unlock(&s->lock);
 
     return 0;
 }
@@ -468,6 +471,7 @@ static int blkdebug_open(BlockDriverState *bs, QDict *options, int flags,
     int ret;
     uint64_t align;
 
+    qemu_mutex_init(&s->lock);
     opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
     if (!qemu_opts_absorb_qdict(opts, options, errp)) {
         ret = -EINVAL;
@@ -568,6 +572,7 @@ static int blkdebug_open(BlockDriverState *bs, QDict *options, int flags,
     ret = 0;
 out:
     if (ret < 0) {
+        qemu_mutex_destroy(&s->lock);
         g_free(s->config_file);
     }
     qemu_opts_del(opts);
@@ -582,6 +587,7 @@ static int rule_check(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
     int error;
     bool immediately;
 
+    qemu_mutex_lock(&s->lock);
     QSIMPLEQ_FOREACH(rule, &s->active_rules, active_next) {
         uint64_t inject_offset = rule->options.inject.offset;
 
@@ -595,6 +601,7 @@ static int rule_check(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
     }
 
     if (!rule || !rule->options.inject.error) {
+        qemu_mutex_unlock(&s->lock);
         return 0;
     }
 
@@ -606,6 +613,7 @@ static int rule_check(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
         remove_rule(rule);
     }
 
+    qemu_mutex_unlock(&s->lock);
     if (!immediately) {
         aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self());
         qemu_coroutine_yield();
@@ -771,8 +779,10 @@ static void blkdebug_close(BlockDriverState *bs)
     }
 
     g_free(s->config_file);
+    qemu_mutex_destroy(&s->lock);
 }
 
+/* Called with lock held.  */
 static void suspend_request(BlockDriverState *bs, BlkdebugRule *rule)
 {
     BDRVBlkdebugState *s = bs->opaque;
@@ -791,6 +801,7 @@ static void suspend_request(BlockDriverState *bs, BlkdebugRule *rule)
     }
 }
 
+/* Called with lock held.  */
 static void process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
                          int *action_count)
 {
@@ -829,9 +840,11 @@ static void blkdebug_debug_event(BlockDriverState *bs, BlkdebugEvent event)
 
     assert((int)event >= 0 && event < BLKDBG__MAX);
 
-    s->new_state = s->state;
-    QLIST_FOREACH_SAFE(rule, &s->rules[event], next, next) {
-        process_rule(bs, rule, actions_count);
+    WITH_QEMU_LOCK_GUARD(&s->lock) {
+        s->new_state = s->state;
+        QLIST_FOREACH_SAFE(rule, &s->rules[event], next, next) {
+            process_rule(bs, rule, actions_count);
+        }
     }
 
     while (actions_count[ACTION_SUSPEND] > 0) {
@@ -839,7 +852,9 @@ static void blkdebug_debug_event(BlockDriverState *bs, BlkdebugEvent event)
         actions_count[ACTION_SUSPEND]--;
     }
 
+    qemu_mutex_lock(&s->lock);
     s->state = s->new_state;
+    qemu_mutex_unlock(&s->lock);
 }
 
 static int blkdebug_debug_breakpoint(BlockDriverState *bs, const char *event,
@@ -862,11 +877,14 @@ static int blkdebug_debug_breakpoint(BlockDriverState *bs, const char *event,
         .options.suspend.tag = g_strdup(tag),
     };
 
+    qemu_mutex_lock(&s->lock);
     QLIST_INSERT_HEAD(&s->rules[blkdebug_event], rule, next);
+    qemu_mutex_unlock(&s->lock);
 
     return 0;
 }
 
+/* Called with lock held.  */
 static int resume_req_by_tag(BDRVBlkdebugState *s, const char *tag, bool all)
 {
     BlkdebugSuspendedReq *r;
@@ -884,7 +902,9 @@ retry:
             g_free(r->tag);
             g_free(r);
 
+            qemu_mutex_unlock(&s->lock);
             qemu_coroutine_enter(co);
+            qemu_mutex_lock(&s->lock);
 
             if (all) {
                 goto retry;
@@ -898,8 +918,12 @@ retry:
 static int blkdebug_debug_resume(BlockDriverState *bs, const char *tag)
 {
     BDRVBlkdebugState *s = bs->opaque;
+    int rc;
 
-    return resume_req_by_tag(s, tag, false);
+    qemu_mutex_lock(&s->lock);
+    rc = resume_req_by_tag(s, tag, false);
+    qemu_mutex_unlock(&s->lock);
+    return rc;
 }
 
 static int blkdebug_debug_remove_breakpoint(BlockDriverState *bs,
@@ -909,17 +933,19 @@ static int blkdebug_debug_remove_breakpoint(BlockDriverState *bs,
     BlkdebugRule *rule, *next;
     int i, ret = -ENOENT;
 
-    for (i = 0; i < BLKDBG__MAX; i++) {
-        QLIST_FOREACH_SAFE(rule, &s->rules[i], next, next) {
-            if (rule->action == ACTION_SUSPEND &&
-                !strcmp(rule->options.suspend.tag, tag)) {
-                remove_rule(rule);
-                ret = 0;
+    WITH_QEMU_LOCK_GUARD(&s->lock) {
+        for (i = 0; i < BLKDBG__MAX; i++) {
+            QLIST_FOREACH_SAFE(rule, &s->rules[i], next, next) {
+                if (rule->action == ACTION_SUSPEND &&
+                    !strcmp(rule->options.suspend.tag, tag)) {
+                    remove_rule(rule);
+                    ret = 0;
+                }
             }
         }
-    }
-    if (resume_req_by_tag(s, tag, true) == 0) {
-        ret = 0;
+        if (resume_req_by_tag(s, tag, true) == 0) {
+            ret = 0;
+        }
     }
     return ret;
 }
@@ -929,6 +955,7 @@ static bool blkdebug_debug_is_suspended(BlockDriverState *bs, const char *tag)
     BDRVBlkdebugState *s = bs->opaque;
     BlkdebugSuspendedReq *r;
 
+    QEMU_LOCK_GUARD(&s->lock);
     QLIST_FOREACH(r, &s->suspended_reqs, next) {
         if (!strcmp(r->tag, tag)) {
             return true;
