Unborking some threading code

[tpg/acess2.git] / Kernel / arch / x86 / include / arch.h

diff --git a/Kernel/arch/x86/include/arch.h b/Kernel/arch/x86/include/arch.h
index 67a6290..0fec144 100644 (file)
--- a/Kernel/arch/x86/include/arch.h
+++ b/Kernel/arch/x86/include/arch.h
@@ -29,47 +29,70 @@
 
 #define __ASM__        __asm__ __volatile__
 
-#define LONGLOCK_NUM_THREADS   8
-
-// === MACROS ===
+// === Spinlocks ===
+/**
+ * \brief Short Spinlock structure
+ */
 struct sShortSpinlock {
-       volatile int    Lock;
-        int    IF;
+       volatile int    Lock;   //!< Lock value
+        int    IF;     //!< Interrupt state on call to SHORTLOCK
 };
 /**
  * \brief Determine if a short spinlock is locked
+ * \param Lock Lock pointer
  */
 static inline int IS_LOCKED(struct sShortSpinlock *Lock) {
        return !!Lock->Lock;
 }
 /**
  * \brief Acquire a Short Spinlock
- * \note Stops interrupts, so be careful
+ * \param Lock Lock pointer
+ * 
+ * This type of mutex should only be used for very short sections of code,
+ * or in places where a Mutex_* would be overkill, such as appending
+ * an element to linked list (usually two assignement lines in C)
+ * 
+ * \note This type of lock halts interrupts, so ensure that no timing
+ * functions are called while it is held.
  */
 static inline void SHORTLOCK(struct sShortSpinlock *Lock) {
         int    v = 1;
-       __ASM__ ("pushf;\n\tpop %%eax" : "=a"(Lock->IF));
-       Lock->IF &= 0x200;
-       __ASM__ ("cli");        // Stop task switches
+        int    IF;
+       // int  val = GetCPUNum() + 1;
+       
+       // Save interrupt state and clear interrupts
+       __ASM__ ("pushf;\n\tcli;\n\tpop %%eax" : "=a"(IF));
+       IF &= 0x200;
+       
        // Wait for another CPU to release
        while(v)
-               __ASM__("xchgl %%eax, (%%edi)":"=a"(v):"a"(1),"D"(&Lock->Lock));
+               __ASM__("xchgl %%ecx, (%%edi)":"=c"(v):"a"(1),"D"(&Lock->Lock));
+       
+       Lock->IF = IF;
 }
 /**
  * \brief Release a short lock
+ * \param Lock Lock pointer
  */
 static inline void SHORTREL(struct sShortSpinlock *Lock) {
-       Lock->Lock = 0;
-       #if 0
-       __ASM__ ("pushf;\n\tor %0, (%%esp);\n\tpopf" : : "a"(Lock->IF));
-       #else
-       if(Lock->IF)    __ASM__ ("sti");
-       #endif
+       // Lock->IF can change anytime once Lock->Lock is zeroed
+       if(Lock->IF) {
+               Lock->Lock = 0;
+               __ASM__ ("sti");
+       }
+       else {
+               Lock->Lock = 0;
+       }
 }
+
+// === MACROS ===
 /**
  * \brief Halt the CPU
  */
 #define        HALT()  __asm__ __volatile__ ("hlt")
+/**
+ * \brief Fire a magic breakpoint (bochs)
+ */
 #define        MAGIC_BREAK()   __asm__ __volatile__ ("xchg %bx, %bx")
 
 // === TYPES ===