linux-kernel - [PATCH] powerpc/xmon: Fix an unexpected xmon onoff state change

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Date:   Wed, 15 Feb 2017 02:49:50 -0500
From:   Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        npiggin@...il.com, gpiccoli@...ux.vnet.ibm.com,
        Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Subject: [PATCH] powerpc/xmon: Fix an unexpected xmon onoff state change

Once xmon is triggered by sysrq-x, it is enabled always afterwards even
if it is disabled during boot. This will cause a system reset interrut
fail to dump. So keep xmon in its original state after exit.

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
---
 arch/powerpc/xmon/xmon.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 9c0e17c..721212f 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -76,6 +76,7 @@ static int xmon_gate;
 #endif /* CONFIG_SMP */
 
 static unsigned long in_xmon __read_mostly = 0;
+static int xmon_off = 0;
 
 static unsigned long adrs;
 static int size = 1;
@@ -3250,6 +3251,8 @@ static void sysrq_handle_xmon(int key)
 	/* ensure xmon is enabled */
 	xmon_init(1);
 	debugger(get_irq_regs());
+	if (xmon_off)
+		xmon_init(0);
 }
 
 static struct sysrq_key_op sysrq_xmon_op = {
@@ -3266,7 +3269,7 @@ static int __init setup_xmon_sysrq(void)
 __initcall(setup_xmon_sysrq);
 #endif /* CONFIG_MAGIC_SYSRQ */
 
-static int __initdata xmon_early, xmon_off;
+static int __initdata xmon_early;
 
 static int __init early_parse_xmon(char *p)
 {
-- 
2.4.11