* lib.c
*/
#include <acess.h>
+#include <threads.h>
+
+#define TRACE_LOCKS 1
+
+extern int GetCPUNum(void);
// === CODE ===
-void Spinlock(int *lock)
+/**
+ * \brief Determine if a short spinlock is locked
+ * \param Lock Lock pointer
+ */
+int IS_LOCKED(struct sShortSpinlock *Lock)
{
- int v = 1;
- while(v) __asm__ __volatile__ ("lock xchgl %%eax, (%%edi)":"=a"(v):"a"(1),"D"(lock));
+ return !!Lock->Lock;
}
-void Release(int *lock)
+/**
+ * \brief Check if the current CPU has the lock
+ * \param Lock Lock pointer
+ */
+int CPU_HAS_LOCK(struct sShortSpinlock *Lock)
+{
+ #if STACKED_LOCKS == 1
+ return Lock->Lock == GetCPUNum() + 1;
+ #elif STACKED_LOCKS == 2
+ return Lock->Lock == Proc_GetCurThread();
+ #else
+ return 0;
+ #endif
+}
+
+/**
+ * \brief Acquire a Short Spinlock
+ * \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. As a matter of fact, spend as
+ * little time as possible with this lock held
+ * \note If \a STACKED_LOCKS is set, this type of spinlock can be nested
+ */
+void SHORTLOCK(struct sShortSpinlock *Lock)
+{
+ int v = 1;
+ #if LOCK_DISABLE_INTS
+ int IF;
+ #endif
+ #if STACKED_LOCKS == 1
+ int cpu = GetCPUNum() + 1;
+ #elif STACKED_LOCKS == 2
+ void *thread = Proc_GetCurThread();
+ #endif
+
+ #if LOCK_DISABLE_INTS
+ // Save interrupt state
+ __ASM__ ("pushf;\n\tpop %0" : "=r"(IF));
+ IF &= 0x200; // AND out all but the interrupt flag
+ #endif
+
+ #if STACKED_LOCKS == 1
+ if( Lock->Lock == cpu ) {
+ Lock->Depth ++;
+ return ;
+ }
+ #elif STACKED_LOCKS == 2
+ if( Lock->Lock == thread ) {
+ Lock->Depth ++;
+ return ;
+ }
+ #endif
+
+ // Wait for another CPU to release
+ while(v) {
+ // CMPXCHG:
+ // If r/m32 == EAX, set ZF and set r/m32 = r32
+ // Else, clear ZF and set EAX = r/m32
+ #if STACKED_LOCKS == 1
+ __ASM__("lock cmpxchgl %2, (%3)"
+ : "=a"(v)
+ : "a"(0), "r"(cpu), "r"(&Lock->Lock)
+ );
+ #elif STACKED_LOCKS == 2
+ __ASM__("lock cmpxchgl %2, (%3)"
+ : "=a"(v)
+ : "a"(0), "r"(thread), "r"(&Lock->Lock)
+ );
+ #else
+ __ASM__("xchgl %%eax, (%%edi)":"=a"(v):"a"(1),"D"(&Lock->Lock));
+ #endif
+
+ #if LOCK_DISABLE_INTS
+ if( v ) __ASM__("sti"); // Re-enable interrupts
+ #endif
+ }
+
+ #if LOCK_DISABLE_INTS
+ __ASM__("cli");
+ Lock->IF = IF;
+ #endif
+
+ #if TRACE_LOCKS
+ Log_Log("LOCK", "%p locked by %p\n", Lock, __builtin_return_address(0));
+ #endif
+}
+/**
+ * \brief Release a short lock
+ * \param Lock Lock pointer
+ */
+void SHORTREL(struct sShortSpinlock *Lock)
{
- __asm__ __volatile__ ("lock andl $0, (%0)"::"r"(lock));
+ #if TRACE_LOCKS
+ Log_Log("LOCK", "%p released by %p\n", Lock, __builtin_return_address(0));
+ #endif
+
+ #if STACKED_LOCKS
+ if( Lock->Depth ) {
+ Lock->Depth --;
+ return ;
+ }
+ #endif
+
+ #if LOCK_DISABLE_INTS
+ // Lock->IF can change anytime once Lock->Lock is zeroed
+ if(Lock->IF) {
+ Lock->Lock = 0;
+ __ASM__ ("sti");
+ }
+ else {
+ Lock->Lock = 0;
+ }
+ #else
+ Lock->Lock = 0;
+ #endif
}
// === IO Commands ===
*/
int memcmp(const void *m1, const void *m2, size_t Num)
{
+ if( Num == 0 ) return 0; // No bytes are always identical
+
while(Num--)
{
- if(*(Uint8*)m1 != *(Uint8*)m2) break;
+ if(*(Uint8*)m1 != *(Uint8*)m2)
+ return *(Uint8*)m1 - *(Uint8*)m2;
m1 ++;
m2 ++;
}
- return *(Uint8*)m1 - *(Uint8*)m2;
+ return 0;
}
/**
EXPORT(LittleEndian16); EXPORT(BigEndian16);
EXPORT(LittleEndian32); EXPORT(BigEndian32);
+
+EXPORT(SHORTLOCK);
+EXPORT(SHORTREL);
+EXPORT(IS_LOCKED);