erts: Let lock checker allow trylock of same order

for different lock instances.

1 files changed, 16 insertions, 9 deletions

diff --git a/erts/emulator/beam/erl_lock_check.c b/erts/emulator/beam/erl_lock_check.c
index edcfcb4cd7..394e19f2fa 100644
--- a/erts/emulator/beam/erl_lock_check.c
+++ b/erts/emulator/beam/erl_lock_check.c
@@ -194,6 +194,12 @@ struct lc_locked_lock_t_ {
     unsigned int line;
     erts_lock_flags_t flags;
     erts_lock_options_t taken_options;
+    /*
+     * Pointer back to the lock instance if it exists or NULL for proc locks.
+     * If set, we use it to allow trylock of other lock instance
+     * but with identical lock order as an already locked lock.
+     */
+    erts_lc_lock_t *lck;
 };
 
 typedef struct {
@@ -407,6 +413,10 @@ new_locked_lock(lc_thread_t* thr,
     ll->line = line;
     ll->flags = lck->flags;
     ll->taken_options = options;
+    if ((lck->flags & ERTS_LOCK_FLAGS_MASK_TYPE) == ERTS_LOCK_FLAGS_TYPE_PROCLOCK)
+        ll->lck = NULL;
+    else
+        ll->lck = lck;
     return ll;
 }
 
@@ -1005,17 +1015,14 @@ erts_lc_trylock_force_busy_flg(erts_lc_lock_t *lck, erts_lock_options_t options)
 	 */
 
         /* Check that we are not trying to lock this lock twice */
-        while (1) {
-            if (order <= 0) {
-                if (order == 0)
-                    lock_twice("Trylocking", thr, lck, options);
-                break;
-            }
+        do {
+            if (order == 0 && (ll->lck == lck || !ll->lck))
+                lock_twice("Trylocking", thr, lck, options);
             ll = ll->prev;
             if (!ll)
                 break;
             order = compare_locked_by_id_extra(ll, lck);
-        }
+        } while (order >= 0);
 
 #ifndef ERTS_LC_ALLWAYS_FORCE_BUSY_TRYLOCK_ON_LOCK_ORDER_VIOLATION
 	/* We only force busy if a lock order violation would occur
@@ -1064,8 +1071,8 @@ void erts_lc_trylock_flg_x(int locked, erts_lc_lock_t *lck, erts_lock_options_t
 	for (tl_lck = thr->locked.last; tl_lck; tl_lck = tl_lck->prev) {
             int order = compare_locked_by_id_extra(tl_lck, lck);
 	    if (order <= 0) {
-		if (order == 0)
-		    lock_twice("Trylocking", thr, lck, options);
+                if (order == 0 && (tl_lck->lck == lck || !tl_lck->lck))
+                    lock_twice("Trylocking", thr, lck, options);
 		if (locked) {
 		    ll->next = tl_lck->next;
 		    ll->prev = tl_lck;