Changeset 9e889f6 in mainline

Timestamp:

2018-11-11T15:46:26Z (6 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

0b5203b

Parents:

d314571

git-author:

Jakub Jermar <jakub@…> (2018-11-10 14:53:45)

git-committer:

Jakub Jermar <jakub@…> (2018-11-11 15:46:26)

Message:

Switch userspace futexes to using waitq kobjects

This replaces futexes entirely when they are not shared across address
spaces.

Location:

uspace/lib/c/generic

Files:

• private/futex.h (modified) (5 diffs)
• thread/futex.c (modified) (1 diff)

uspace/lib/c/generic/private/futex.h

@@ -42 +42 @@
 #include <time.h>
 #include <fibril.h>
+#include <abi/cap.h>
 
 typedef struct futex {
         volatile atomic_int val;
+        volatile atomic_int alloc_lock;
+        cap_waitq_handle_t whandle;
+
 #ifdef CONFIG_DEBUG_FUTEX
         _Atomic(fibril_t *) owner;
@@ -54 +58 @@
 #ifdef CONFIG_DEBUG_FUTEX
 
-#define FUTEX_INITIALIZE(val) { (val) , NULL }
+#define FUTEX_INITIALIZE(val) { (val), 0, CAP_NIL, NULL }
 #define FUTEX_INITIALIZER     FUTEX_INITIALIZE(1)
 
@@ -74 +78 @@
 #else
 
-#define FUTEX_INITIALIZE(val) { (val) }
+#define FUTEX_INITIALIZE(val) { (val), 0, CAP_NIL }
 #define FUTEX_INITIALIZER     FUTEX_INITIALIZE(1)
 
@@ -132 +136 @@
         }
 
-        return __SYSCALL2(SYS_FUTEX_SLEEP, (sysarg_t) futex, (sysarg_t) timeout);
+        if (futex->whandle == CAP_NIL) {
+                while (atomic_exchange_explicit(&futex->alloc_lock, 1,
+                    memory_order_acquire) == 1)
+                        ;
+                if (futex->whandle == CAP_NIL) {
+                        errno_t rc = __SYSCALL1(SYS_WAITQ_CREATE,
+                            (sysarg_t) &futex->whandle);
+                        if (rc != EOK) {
+                                atomic_store_explicit(&futex->alloc_lock, 0,
+                                    memory_order_release);
+                                return rc;
+                        }
+                }
+
+                atomic_store_explicit(&futex->alloc_lock, 0,
+                    memory_order_release);
+        }
+
+        return __SYSCALL2(SYS_WAITQ_SLEEP, (sysarg_t) futex->whandle,
+            (sysarg_t) timeout);
 }
 
@@ -147 +170 @@
 {
         if (atomic_fetch_add_explicit(&futex->val, 1, memory_order_release) < 0)
-                return __SYSCALL1(SYS_FUTEX_WAKEUP, (sysarg_t) futex);
+                return __SYSCALL1(SYS_WAITQ_WAKEUP, (sysarg_t) futex->whandle);
 
         return EOK;

uspace/lib/c/generic/thread/futex.c

@@ -53 +53 @@
 {
         atomic_store_explicit(&futex->val, val, memory_order_relaxed);
+        atomic_store_explicit(&futex->alloc_lock, 0, memory_order_relaxed);
+        futex->whandle = CAP_NIL;
 }