christoph/lecture-operating-system-development
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merged cleanup

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This commit is contained in:
Christoph Urlacher
2022-07-24 21:12:31 +02:00
parent 5ff3d72bfd
commit 6481bae5f6
92 changed files with 663 additions and 755 deletions
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7
c_os/lib/SpinLock.cc
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@ -10,7 +10,6 @@
*****************************************************************************/
#include "lib/SpinLock.h"
#include "kernel/Globals.h"
/*****************************************************************************
* Methode: CAS *
@ -24,7 +23,7 @@
* *ptr := _new *
* return prev *
*****************************************************************************/
static inline unsigned long CAS(unsigned long* ptr, unsigned long old, unsigned long _new) {
static inline unsigned long CAS(const unsigned long* ptr) {
unsigned long prev;
/*
@ -38,7 +37,7 @@ static inline unsigned long CAS(unsigned long* ptr, unsigned long old, unsigned
"cmpxchg %1, %2;" // %1 = _new; %2 = *ptr
// constraints
: "=a"(prev) // output: =a: RAX -> prev (%0))
: "r"(_new), "m"(*ptr), "a"(old) // input = %1, %2, %3 (r=register, m=memory, a=accumlator = eax
: "r"(1), "m"(*ptr), "a"(0) // input = %1, %2, %3 (r=register, m=memory, a=accumlator = eax
: "memory"); // ensures assembly block will not be moved by gcc
return prev; // return pointer instead of prev to prevent unnecessary second call
@ -52,7 +51,7 @@ static inline unsigned long CAS(unsigned long* ptr, unsigned long old, unsigned
void SpinLock::acquire() {
// If lock == 0 the SpinLock can be aquired without waiting
// If lock == 1 the while loop blocks until aquired
while (CAS(ptr, 0, 1) != 0) {}
while (CAS(ptr) != 0) {}
}
/*****************************************************************************