Fiddling with threading code to attempt to fix this ____ bug

[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 464023e..b3f7545 100644 (file)
--- a/Kernel/arch/x86/include/arch.h
+++ b/Kernel/arch/x86/include/arch.h
@@ -10,6 +10,9 @@
 #define        KERNEL_BASE     0xC0000000
 #define BITS   32
 
+// Allow nested spinlocks?
+#define STACKED_LOCKS  1
+
 // - Processor/Machine Specific Features
 #if ARCH != i386 && ARCH != i486 && ARCH != i586
 # error "Unknown architecture '" #ARCH "'"
@@ -36,6 +39,9 @@
 struct sShortSpinlock {
        volatile int    Lock;   //!< Lock value
         int    IF;     //!< Interrupt state on call to SHORTLOCK
+       #if STACKED_LOCKS
+        int    Depth;
+       #endif
 };
 /**
  * \brief Determine if a short spinlock is locked
@@ -53,20 +59,42 @@ static inline int IS_LOCKED(struct sShortSpinlock *Lock) {
  * 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.
+ * functions are called while it is held. As a matter of fact, spend as
+ * little time as possible with this lock held
  */
 static inline void SHORTLOCK(struct sShortSpinlock *Lock) {
         int    v = 1;
         int    IF;
-       // int  cpu = GetCPUNum() + 1;
+       #if STACKED_LOCKS
+       extern int      GetCPUNum(void);
+        int    cpu = GetCPUNum() + 1;
+       #endif
        
        // Save interrupt state and clear interrupts
        __ASM__ ("pushf;\n\tpop %%eax\n\tcli" : "=a"(IF));
        IF &= 0x200;    // AND out all but the interrupt flag
        
+       #if STACKED_LOCKS
+       if( Lock->Lock == cpu ) {
+               Lock->Depth ++;
+               return ;
+       }
+       #endif
+       
        // Wait for another CPU to release
-       while(v)
+       while(v) {
+               #if STACKED_LOCKS
+               // CMPXCHG:
+               //  If r/m32 == EAX, set ZF and set r/m32 = r32
+               //  Else, clear ZF and set EAX = r/m32
+               __ASM__("lock cmpxchgl %%ecx, (%%edi)"
+                       : "=a"(v)
+                       : "a"(0), "c"(cpu), "D"(&Lock->Lock)
+                       );
+               #else
                __ASM__("xchgl %%eax, (%%edi)":"=a"(v):"a"(1),"D"(&Lock->Lock));
+               #endif
+       }
        
        Lock->IF = IF;
 }
@@ -75,6 +103,12 @@ static inline void SHORTLOCK(struct sShortSpinlock *Lock) {
  * \param Lock Lock pointer
  */
 static inline void SHORTREL(struct sShortSpinlock *Lock) {
+       #if STACKED_LOCKS
+       if( Lock->Depth ) {
+               Lock->Depth --;
+               return ;
+       }
+       #endif
        // Lock->IF can change anytime once Lock->Lock is zeroed
        if(Lock->IF) {
                Lock->Lock = 0;