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From 4552d128c26e0f0f27a5bd2fadc24092b8f6c1d7 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Sun, 24 Dec 2017 02:49:22 +1000
Subject: [PATCH] powerpc: System reset avoid interleaving oops using die
 synchronisation

References: bsc#1086791
Patch-mainline: v4.16-rc1
Git-commit: 4552d128c26e0f0f27a5bd2fadc24092b8f6c1d7

The die() oops path contains a serializing lock to prevent oops
messages from being interleaved. In the case of a system reset
initiated oops (e.g., qemu nmi command), __die was being called
which lacks that synchronisation and oops reports could be
interleaved across CPUs.

A recent patch 4388c9b3a6ee7 ("powerpc: Do not send system reset
request through the oops path") changed this to __die to avoid
the debugger() call, but there is no real harm to calling it twice
if the first time fell through. So go back to using die() here.
This was observed to fix the problem.

Fixes: 4388c9b3a6ee7 ("powerpc: Do not send system reset request through the oops path")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index d61989be28e1..d139117d3339 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -337,7 +337,7 @@ void system_reset_exception(struct pt_regs *regs)
 	 * No debugger or crash dump registered, print logs then
 	 * panic.
 	 */
-	__die("System Reset", regs, SIGABRT);
+	die("System Reset", regs, SIGABRT);
 
 	mdelay(2*MSEC_PER_SEC); /* Wait a little while for others to print */
 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
-- 
2.13.6