Set thread priorities on multithreaded CPUs so that threads holding a

spinlock are high-priority and threads waiting for a spinlock are set to
low priority.

2 files changed, 5 insertions, 2 deletions

diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index 2980b09..92a06d2 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -750,6 +750,7 @@ spinlock_enter(void)
 
 	td = curthread;
 	if (td->td_md.md_spinlock_count == 0) {
+		__asm __volatile("or 2,2,2"); /* Set high thread priority */
 		msr = intr_disable();
 		td->td_md.md_spinlock_count = 1;
 		td->td_md.md_saved_msr = msr;
@@ -768,8 +769,10 @@ spinlock_exit(void)
 	critical_exit();
 	msr = td->td_md.md_saved_msr;
 	td->td_md.md_spinlock_count--;
-	if (td->td_md.md_spinlock_count == 0)
+	if (td->td_md.md_spinlock_count == 0) {
 		intr_restore(msr);
+		__asm __volatile("or 6,6,6"); /* Set normal thread priority */
+	}
 }
 
 int db_trap_glue(struct trapframe *);		/* Called from trap_subr.S */
diff --git a/sys/powerpc/include/cpu.h b/sys/powerpc/include/cpu.h
index 6ef9882..65358a6 100644
--- a/sys/powerpc/include/cpu.h
+++ b/sys/powerpc/include/cpu.h
@@ -88,7 +88,7 @@ get_cyclecount(void)
 }
 
 #define	cpu_getstack(td)	((td)->td_frame->fixreg[1])
-#define	cpu_spinwait()		/* nothing */
+#define	cpu_spinwait()		__asm __volatile("or 27,27,27") /* yield */
 
 extern char btext[];
 extern char etext[];