spinlocks

1 files changed, 8 insertions, 10 deletions

diff --git a/kernel/x86.c b/kernel/x86.c
index 7775ab7..15236a3 100644
--- a/kernel/x86.c
+++ b/kernel/x86.c
@@ -4,6 +4,10 @@
 #include "lib/int/stdint.h"
 #include "lib/logger/log.h"
 
+//
+// suffix (b, w, l, q for byte, word, dword, and qword).
+//
+
 extern volatile uint64_t task_system_clock; // from task.c
 
 void sleep(int i)
@@ -139,25 +143,19 @@ void x86_flush_tlb(uint32_t addr)
 }
 
 //xchg
-volatile uint8_t x86_xchg(volatile uint8_t *addr, uint8_t val)
+uint8_t x86_xchg(uint8_t *addr, uint8_t val)
 {   
-  uint8_t result;
 
-  // test. because asm does not work !?
-  uint8_t oldval=*addr;
-  *addr=val;
-   return oldval;
-    
+  uint8_t result;
 
-  
   // The + in "+m" denotes a read-modify-write operand.
-  asm volatile("lock xchg %0, %1" :
+  asm volatile("lock xchgb %0, %1" :
                "+m" (*addr), "=a" (result) :
                "1" (val) :
                "cc");
 
  //log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"xchg val:%d with addr:0x%08X : result: %d",val,addr,result);
-//
+ 
   return result;
 }