Changeset 42f5860 in mainline

Timestamp:

2018-07-18T19:56:49Z (6 years ago)

Author:

Jiří Zárevúcky <jiri.zarevucky@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

9d8307a

Parents:

9bde0d5

git-author:

Jiří Zárevúcky <jiri.zarevucky@…> (2018-07-13 23:13:27)

git-committer:

Jiří Zárevúcky <jiri.zarevucky@…> (2018-07-18 19:56:49)

Message:

Clean up userspace RCU.

File:

• uspace/lib/c/generic/rcu.c (modified) (10 diffs)

uspace/lib/c/generic/rcu.c

@@ -105 +105 @@
         size_t cur_gp;
         size_t reader_group;
-        futex_t list_futex;
+        fibril_rmutex_t list_mutex;
         list_t fibrils_list;
         struct {
-                futex_t futex;
+                fibril_rmutex_t mutex;
                 bool locked;
                 list_t blocked_fibrils;
-                size_t blocked_thread_cnt;
-                futex_t futex_blocking_threads;
         } sync_lock;
 } rcu_data_t;
@@ -137 +135 @@
         .cur_gp = 0,
         .reader_group = RCU_GROUP_A,
-        .list_futex = FUTEX_INITIALIZER,
+        .list_mutex = FIBRIL_RMUTEX_INITIALIZER(rcu.list_mutex),
         .fibrils_list = LIST_INITIALIZER(rcu.fibrils_list),
         .sync_lock = {
-                .futex = FUTEX_INITIALIZER,
+                .mutex = FIBRIL_RMUTEX_INITIALIZER(rcu.sync_lock.mutex),
                 .locked = false,
                 .blocked_fibrils = LIST_INITIALIZER(rcu.sync_lock.blocked_fibrils),
-                .blocked_thread_cnt = 0,
-                .futex_blocking_threads = FUTEX_INITIALIZE(0),
         },
 };
@@ -171 +167 @@
         assert(!fibril_rcu.registered);
 
-        futex_lock(&rcu.list_futex);
+        fibril_rmutex_lock(&rcu.list_mutex);
         list_append(&fibril_rcu.link, &rcu.fibrils_list);
-        futex_unlock(&rcu.list_futex);
+        fibril_rmutex_unlock(&rcu.list_mutex);
 
         fibril_rcu.registered = true;
@@ -196 +192 @@
         fibril_rcu.nesting_cnt = 0;
 
-        futex_lock(&rcu.list_futex);
+        fibril_rmutex_lock(&rcu.list_mutex);
         list_remove(&fibril_rcu.link);
-        futex_unlock(&rcu.list_futex);
+        fibril_rmutex_unlock(&rcu.list_mutex);
 
         fibril_rcu.registered = false;
@@ -333 +329 @@
 static void wait_for_readers(size_t reader_group)
 {
-        futex_lock(&rcu.list_futex);
+        fibril_rmutex_lock(&rcu.list_mutex);
 
         list_t quiescent_fibrils;
@@ -344 +340 @@
 
                         if (is_preexisting_reader(fib, reader_group)) {
-                                futex_unlock(&rcu.list_futex);
+                                fibril_rmutex_unlock(&rcu.list_mutex);
                                 sync_sleep();
-                                futex_lock(&rcu.list_futex);
+                                fibril_rmutex_lock(&rcu.list_mutex);
                                 /* Break to while loop. */
                                 break;
@@ -357 +353 @@
 
         list_concat(&rcu.fibrils_list, &quiescent_fibrils);
-        futex_unlock(&rcu.list_futex);
+        fibril_rmutex_unlock(&rcu.list_mutex);
 }
 
 static void lock_sync(void)
 {
-        futex_lock(&rcu.sync_lock.futex);
+        fibril_rmutex_lock(&rcu.sync_lock.mutex);
         if (rcu.sync_lock.locked) {
                 blocked_fibril_t blocked_fib;
@@ -371 +367 @@
                 do {
                         blocked_fib.is_ready = false;
-                        futex_unlock(&rcu.sync_lock.futex);
+                        fibril_rmutex_unlock(&rcu.sync_lock.mutex);
                         futex_lock(&async_futex);
                         fibril_switch(FIBRIL_FROM_BLOCKED);
                         futex_unlock(&async_futex);
-                        futex_lock(&rcu.sync_lock.futex);
+                        fibril_rmutex_lock(&rcu.sync_lock.mutex);
                 } while (rcu.sync_lock.locked);
 
@@ -389 +385 @@
         assert(rcu.sync_lock.locked);
 
-        /*
-         * Blocked threads have a priority over fibrils when accessing sync().
-         * Pass the lock onto a waiting thread.
-         */
-        if (0 < rcu.sync_lock.blocked_thread_cnt) {
-                --rcu.sync_lock.blocked_thread_cnt;
-                futex_unlock(&rcu.sync_lock.futex_blocking_threads);
-        } else {
-                /* Unlock but wake up any fibrils waiting for the lock. */
-
-                if (!list_empty(&rcu.sync_lock.blocked_fibrils)) {
-                        blocked_fibril_t *blocked_fib = member_to_inst(
-                            list_first(&rcu.sync_lock.blocked_fibrils), blocked_fibril_t, link);
-
-                        if (!blocked_fib->is_ready) {
-                                blocked_fib->is_ready = true;
-                                fibril_add_ready(blocked_fib->id);
-                        }
+        /* Unlock but wake up any fibrils waiting for the lock. */
+
+        if (!list_empty(&rcu.sync_lock.blocked_fibrils)) {
+                blocked_fibril_t *blocked_fib = member_to_inst(
+                    list_first(&rcu.sync_lock.blocked_fibrils), blocked_fibril_t, link);
+
+                if (!blocked_fib->is_ready) {
+                        blocked_fib->is_ready = true;
+                        fibril_add_ready(blocked_fib->id);
                 }
-
-                rcu.sync_lock.locked = false;
-                futex_unlock(&rcu.sync_lock.futex);
         }
+
+        rcu.sync_lock.locked = false;
+        fibril_rmutex_unlock(&rcu.sync_lock.mutex);
 }
 
@@ -421 +408 @@
          * but keep sync locked.
          */
-        futex_unlock(&rcu.sync_lock.futex);
+        fibril_rmutex_unlock(&rcu.sync_lock.mutex);
         fibril_usleep(RCU_SLEEP_MS * 1000);
-        futex_lock(&rcu.sync_lock.futex);
+        fibril_rmutex_lock(&rcu.sync_lock.mutex);
 }