Changeset 92d34f0b in mainline

Timestamp:

2009-06-11T20:30:59Z (16 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

9ae22ba

Parents:

ba2a055

Message:

Implement readers-writer locks for fibrils.

Location:

uspace/lib/libc

Files:

• generic/fibril_sync.c (modified) (1 diff)
• include/fibril.h (modified) (1 diff)
• include/fibril_sync.h (modified) (1 diff)

uspace/lib/libc/generic/fibril_sync.c

@@ -91 +91 @@
 void fibril_rwlock_initialize(fibril_rwlock_t *frw)
 {
-        fibril_mutex_initialize(&frw->fm);
+        frw->writers = 0;
+        frw->readers = 0;
+        list_initialize(&frw->waiters);
 }
 
 void fibril_rwlock_read_lock(fibril_rwlock_t *frw)
 {
-        fibril_mutex_lock(&frw->fm);
+        futex_down(&async_futex);
+        if (frw->writers) {
+                fibril_t *f = (fibril_t *) fibril_get_id();
+                f->flags &= ~FIBRIL_WRITER;
+                list_append(&f->link, &frw->waiters);
+                fibril_switch(FIBRIL_TO_MANAGER);
+        } else {
+                frw->readers++;
+                futex_up(&async_futex);
+        }
 }
 
 void fibril_rwlock_write_lock(fibril_rwlock_t *frw)
 {
-        fibril_mutex_lock(&frw->fm);
+        futex_down(&async_futex);
+        if (frw->writers || frw->readers) {
+                fibril_t *f = (fibril_t *) fibril_get_id();
+                f->flags |= FIBRIL_WRITER;
+                list_append(&f->link, &frw->waiters);
+                fibril_switch(FIBRIL_TO_MANAGER);
+        } else {
+                frw->writers++;
+                futex_up(&async_futex);
+        }
+}
+
+static void _fibril_rwlock_common_unlock(fibril_rwlock_t *frw)
+{
+        futex_down(&async_futex);
+        assert(frw->readers || (frw->writers == 1));
+        if (frw->readers) {
+                if (--frw->readers)
+                        goto out;
+        } else {
+                frw->writers--;
+        }
+        
+        assert(!frw->readers && !frw->writers);
+        
+        while (!list_empty(&frw->waiters)) {
+                link_t *tmp = frw->waiters.next;
+                fibril_t *f = list_get_instance(tmp, fibril_t, link);
+                
+                if (f->flags & FIBRIL_WRITER) {
+                        if (frw->readers)
+                                break;
+                        list_remove(&f->link);
+                        fibril_add_ready((fid_t) f);
+                        frw->writers++;
+                        break;
+                } else {
+                        list_remove(&f->link);
+                        fibril_add_ready((fid_t) f);
+                        frw->readers++;
+                }
+        }
+out:
+        futex_up(&async_futex);
 }
 
 void fibril_rwlock_read_unlock(fibril_rwlock_t *frw)
 {
-        fibril_mutex_unlock(&frw->fm);
+        _fibril_rwlock_common_unlock(frw);
 }
 
 void fibril_rwlock_write_unlock(fibril_rwlock_t *frw)
 {
-        fibril_mutex_unlock(&frw->fm);
+        _fibril_rwlock_common_unlock(frw);
 }
 

uspace/lib/libc/include/fibril.h

@@ -47 +47 @@
 #endif /* context_set */
 
-#define FIBRIL_SERIALIZED  1
+#define FIBRIL_SERIALIZED       1
+#define FIBRIL_WRITER           2
 
 typedef enum {

uspace/lib/libc/include/fibril_sync.h

@@ -56 +56 @@
 
 typedef struct {
-        fibril_mutex_t fm;
+        unsigned writers;
+        unsigned readers;
+        link_t waiters;
 } fibril_rwlock_t;
 
 #define FIBRIL_RWLOCK_INITIALIZE(name) \
         fibril_rwlock_t name = { \
-                .fm = { \
-                        .counter = 1, \
-                        .waiters = { \
-                                .prev = &name.fm.waiters, \
-                                .next = &name.fm.waiters, \
-                        } \
+                .readers = 0, \
+                .writers = 0, \
+                .waiters = { \
+                        .prev = &name.waiters, \
+                        .next = &name.waiters, \
                 } \
         }