core: Make secondary spin and locks use cpu_relax()

This makes secondaries spinning waiting for a job and spinlocks
use cpu_relax() which speeds up the primary thread and thus speeds
up the boot process a bit. Also prettify a bit cpu_relax() implementation

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 6 insertions, 9 deletions

diff --git a/core/cpu.c b/core/cpu.c
index cefb1f0..f962d7c 100644
--- a/core/cpu.c
+++ b/core/cpu.c
@@ -67,11 +67,10 @@ void cpu_relax(void)
 	/* Relax a bit to give sibling threads some breathing space */
 	smt_low();
 	smt_very_low();
-	asm volatile("nop; nop; nop\n");
-	asm volatile("nop; nop; nop\n");
-	asm volatile("nop; nop; nop\n");
-	asm volatile("nop; nop; nop\n");
-	asm volatile("nop; nop; nop\n");
+	asm volatile("nop; nop; nop; nop\n");
+	asm volatile("nop; nop; nop; nop\n");
+	asm volatile("nop; nop; nop; nop\n");
+	asm volatile("nop; nop; nop; nop\n");
 	smt_medium();
 }
 
diff --git a/core/init.c b/core/init.c
index 99d17f1..a1d6f44 100644
--- a/core/init.c
+++ b/core/init.c
@@ -673,8 +673,7 @@ void __noreturn __secondary_cpu_entry(void)
 		/* Relax a bit to give the simulator some breathing space */
 		i = 1000;
 		while (--i)
-			smt_very_low();
-		smt_low();
+			cpu_relax();
 	}
 }
 
diff --git a/core/lock.c b/core/lock.c
index 70fb994..6a8282f 100644
--- a/core/lock.c
+++ b/core/lock.c
@@ -87,9 +87,8 @@ void lock(struct lock *l)
 	for (;;) {
 		if (try_lock(l))
 			break;
-		smt_low();
+		cpu_relax();
 	}
-	smt_medium();
 }
 
 void unlock(struct lock *l)