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[SRU,Artful,3/3] powerpc: System reset avoid interleaving oops using die synchronisation

Message ID 810031bce268b18267a118a8e5a45f8ce7f62c01.1528729715.git.joseph.salisbury@canonical.com
State New
Headers show
Series Fixes for LP:1776211 | expand

Commit Message

Joseph Salisbury June 13, 2018, 3:54 p.m. UTC 
From: Nicholas Piggin <npiggin@gmail.com>

BugLink: http://bugs.launchpad.net/bugs/1776211

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>
(cherry picked from commit 4552d128c26e0f0f27a5bd2fadc24092b8f6c1d7)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
---
 arch/powerpc/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 8332c77e..174524b 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -306,7 +306,7 @@  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);