[PATCH] powerpc/kdump: Fix timeout in crash_kexec_wait_realmode

We check for timeout expiry in the outer loop, but we also need to
check it in the inner loop or we can lock up forever waiting for a
CPU to hit real mode.

Signed-off-by: Anton Blanchard <redacted>
Cc: <stable@kernel.org>
---

Index: linux-powerpc/arch/powerpc/kernel/crash.c
===================================================================

--- linux-powerpc.orig/arch/powerpc/kernel/crash.c	2011-07-05 15:04:18.512140484 +1000
+++ linux-powerpc/arch/powerpc/kernel/crash.c	2011-07-05 15:05:51.483747575 +1000

@@ -240,7 +240,8 @@ static void crash_kexec_wait_realmode(in
 		if (i == cpu)
 			continue;
 
-		while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
+		while ((paca[i].kexec_state < KEXEC_STATE_REAL_MODE) &&
+				(msecs > 0)) {
 			barrier();
 			if (!cpu_possible(i)) {
 				break;

The existing code it pretty ugly.  How about we clean it up even more
like this?

From: Anton Blanchard <redacted>

We check for timeout expiry in the outer loop, but we also need to
check it in the inner loop or we can lock up forever waiting for a
CPU to hit real mode.

Signed-off-by: Anton Blanchard <redacted>
Signed-off-by: Michael Neuling <redacted>
Cc: <stable@kernel.org>

diff --git a/arch/powerpc/kernel/crash.c b/arch/powerpc/kernel/crash.c
index 4e6ee94..cc6a9d5 100644
--- a/arch/powerpc/kernel/crash.c
+++ b/arch/powerpc/kernel/crash.c

@@ -242,12 +242,8 @@ static void crash_kexec_wait_realmode(int cpu)
 
 		while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
 			barrier();
-			if (!cpu_possible(i)) {
+			if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
 				break;
-			}
-			if (!cpu_online(i)) {
-				break;
-			}
 			msecs--;
 			mdelay(1);
 		}

On Tue, 05 Jul 2011 16:40:10 +1000
Michael Neuling [off-list ref] wrote:

The existing code it pretty ugly.  How about we clean it up even more
like this?

Looks good and it passed my kdump test cases.

Anton