Changeset a9ef68b in mainline

Timestamp:

2006-04-05T12:12:39Z (19 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

fe04594

Parents:

448743f

Message:

Because of another race condition, futex_wakeup() needs to be able to allocate and initialize the kernel futex structure too.

File:

• generic/src/synch/futex.c (modified) (5 diffs)

generic/src/synch/futex.c

@@ -54 +54 @@
 static void futex_initialize(futex_t *futex);
 
+static futex_t *futex_find(__address paddr);
 static index_t futex_ht_hash(__native *key);
 static bool futex_ht_compare(__native *key, count_t keys, link_t *item);
@@ -102 +103 @@
         futex_t *futex;
         __address paddr;
-        link_t *item;
         pte_t *t;
         ipl_t ipl;
@@ -123 +123 @@
         interrupts_restore(ipl);        
 
+        futex = futex_find(paddr);
+        
+        return (__native) waitq_sleep_timeout(&futex->wq, usec, trydown);
+}
+
+/** Wakeup one thread waiting in futex wait queue.
+ *
+ * @param uaddr Userspace address of the futex counter.
+ *
+ * @return ENOENT if there is no futex associated with the address
+ *         or if there is no physical mapping for uaddr.
+ */
+__native sys_futex_wakeup(__address uaddr)
+{
+        futex_t *futex;
+        __address paddr;
+        pte_t *t;
+        ipl_t ipl;
+        
+        ipl = interrupts_disable();
+        
+        /*
+         * Find physical address of futex counter.
+         */
+        page_table_lock(AS, true);
+        t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
+        if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
+                page_table_unlock(AS, true);
+                interrupts_restore(ipl);
+                return (__native) ENOENT;
+        }
+        paddr = PFN2ADDR(PTE_GET_FRAME(t)) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
+        page_table_unlock(AS, true);
+        
+        interrupts_restore(ipl);
+
+        futex = futex_find(paddr);
+                
+        waitq_wakeup(&futex->wq, WAKEUP_FIRST);
+        
+        return 0;
+}
+
+/** Find kernel address of the futex structure corresponding to paddr.
+ *
+ * If the structure does not exist alreay, a new one is created.
+ *
+ * @param paddr Physical address of the userspace futex counter.
+ *
+ * @return Address of the kernel futex structure.
+ */
+futex_t *futex_find(__address paddr)
+{
+        link_t *item;
+        futex_t *futex;
+        
         /*
          * Find the respective futex structure
@@ -142 +198 @@
                 rwlock_write_lock(&futex_ht_lock);
                 /*
-                 * Detect possible race condition by searching
+                 * Avoid possible race condition by searching
                  * the hash table once again with write access.
                  */
@@ -158 +214 @@
         }
         
-        return (__native) waitq_sleep_timeout(&futex->wq, usec, trydown);
-}
-
-/** Wakeup one thread waiting in futex wait queue.
- *
- * @param uaddr Userspace address of the futex counter.
- *
- * @return ENOENT if there is no futex associated with the address
- *         or if there is no physical mapping for uaddr.
- */
-__native sys_futex_wakeup(__address uaddr)
-{
-        futex_t *futex = NULL;
-        __address paddr;
-        link_t *item;
-        pte_t *t;
-        ipl_t ipl;
-        
-        ipl = interrupts_disable();
-        
-        /*
-         * Find physical address of futex counter.
-         */
-        page_table_lock(AS, true);
-        t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
-        if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
-                page_table_unlock(AS, true);
-                interrupts_restore(ipl);
-                return (__native) ENOENT;
-        }
-        paddr = PFN2ADDR(PTE_GET_FRAME(t)) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
-        page_table_unlock(AS, true);
-        
-        interrupts_restore(ipl);
-
-        /*
-         * Find the respective futex structure.
-         */
-        rwlock_read_lock(&futex_ht_lock);
-        item = hash_table_find(&futex_ht, &paddr);
-        if (item) {
-                futex = hash_table_get_instance(item, futex_t, ht_link);
-        }
-        rwlock_read_unlock(&futex_ht_lock);
-
-        if (!futex)
-                return (__native) ENOENT;       
-                
-        waitq_wakeup(&futex->wq, WAKEUP_FIRST);
-        
-        return 0;
+        return futex;
 }