Changeset cd769305 in mainline for uspace/lib/libc/arch/arm32/include/atomic.h

Timestamp:

2009-12-07T21:57:22Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

216cb85

Parents:

a47d49f

Message:

Implement userspace arm32 cas() and atomic_add() using RAS.

File:

• uspace/lib/libc/arch/arm32/include/atomic.h (modified) (2 diffs)

uspace/lib/libc/arch/arm32/include/atomic.h

@@ -37 +37 @@
 #define LIBC_arm32_ATOMIC_H_
 
+#define LIBC_ARCH_ATOMIC_H_
+#define CAS 
+
+#include <atomicdflt.h>
 #include <bool.h>
+#include <sys/types.h>
 
-typedef struct atomic {
-        volatile long count;
-} atomic_t;
-
-static inline void atomic_set(atomic_t *val, long i)
-{
-        val->count = i;
-}
-
-static inline long atomic_get(atomic_t *val)
-{
-        return val->count;
-}
+extern uintptr_t *ras_page;
 
 static inline bool cas(atomic_t *val, long ov, long nv)
 {
-        /* FIXME: is not atomic */
-        if (val->count == ov) {
-                val->count = nv;
-                return true;
-        }
-        return false;
+        long ret = 0;
+
+        /*
+         * The following instructions between labels 1 and 2 constitute a
+         * Restartable Atomic Seqeunce. Should the sequence be non-atomic,
+         * the kernel will restart it.
+         */
+        asm volatile (
+                "1:\n"
+                "       adr %[ret], 1b\n"
+                "       str %[ret], %[rp0]\n"
+                "       adr %[ret], 2f\n"
+                "       str %[ret], %[rp1]\n"
+                "       ldr %[ret], %[addr]\n"
+                "       cmp %[ret], %[ov]\n"
+                "       streq %[nv], %[addr]\n"
+                "2:\n"
+                "       moveq %[ret], #1\n"
+                "       movne %[ret], #0\n"
+                : [ret] "+&r" (ret),
+                  [rp0] "=m" (ras_page[0]),
+                  [rp1] "=m" (ras_page[1]),
+                  [addr] "+m" (val->count)
+                : [ov] "r" (ov),
+                  [nv] "r" (nv)
+                : "memory"
+        );
+
+        ras_page[0] = 0;
+        asm volatile ("" ::: "memory"); 
+        ras_page[1] = 0xffffffff;
+
+        return (bool) ret;
 }
 
@@ -72 +92 @@
 static inline long atomic_add(atomic_t *val, int i)
 {
-        int ret;
-        volatile long * mem = &(val->count);
+        long ret = 0;
 
-        /* FIXME: is not atomic, is broken */
+        /*
+         * The following instructions between labels 1 and 2 constitute a
+         * Restartable Atomic Seqeunce. Should the sequence be non-atomic,
+         * the kernel will restart it.
+         */
         asm volatile (
-        "1:\n"
-                "ldr r2, [%1]\n"
-                "add r3, r2, %2\n"
-                "str r3, %0\n"
-                "swp r3, r3, [%1]\n"
-                "cmp r3, r2\n"
-                "bne 1b\n"
+                "1:\n"
+                "       adr %[ret], 1b\n"
+                "       str %[ret], %[rp0]\n"
+                "       adr %[ret], 2f\n"
+                "       str %[ret], %[rp1]\n"
+                "       ldr %[ret], %[addr]\n"
+                "       add %[ret], %[ret], %[imm]\n"
+                "       str %[ret], %[addr]\n"
+                "2:\n"
+                : [ret] "+&r" (ret),
+                  [rp0] "=m" (ras_page[0]),
+                  [rp1] "=m" (ras_page[1]),
+                  [addr] "+m" (val->count)
+                : [imm] "r" (i)
+        );
 
-                : "=m" (ret)
-                : "r" (mem), "r" (i)
-                : "r3", "r2"
-        );
+        ras_page[0] = 0;
+        asm volatile ("" ::: "memory"); 
+        ras_page[1] = 0xffffffff;
 
         return ret;