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[tpg/acess2.git] / Notes / Spinlocks.txt

diff --git a/Notes/Spinlocks.txt b/Notes/Spinlocks.txt
new file mode 100644 (file)
index 0000000..b4f6b84
--- /dev/null
+++ b/Notes/Spinlocks.txt
@@ -0,0 +1,26 @@
+SHORTLOCK()
+       cli; lock cmpxchg
+SHORTREL()
+       lock and ; sti
+
+
+LONGLOCK()
+       mov eax, 1
+       lock cmpxchg lock.lock, eax
+       if(eax) {
+               SHORTLOCK(lock.listLock)
+               // add to list (linked list, 4 static entries)
+               SHORTREL(lock.listLock)
+               for(;;)
+               {
+                       check owner
+                       mov eax, 1
+                       lock cmpxchg lock.lock, eax
+                       if(!eax)        break;  // got lock
+                       Threads_Sleep();
+               }
+       }
+
+LONGREL()
+       lock and lock.lock, 0
+       pop off front of list, free entry, wake thread