[PATCH] powerpc/xmon: add turn off xmon option

[Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>]

Once xmon is triggered, there is no interface to turn it off again.
However there exists disable/enable xmon code flows. And more important,
System reset interrupt on powerVM will fire an oops to make a dump. At
that time, xmon should not be triggered.

So add 'z' option after current 'x|X' exit commands. Turn xmon off if 'z'
is following.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/xmon/xmon.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 9c0e17c..2f4e7b1 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;
@@ -255,8 +256,8 @@ Commands:\n\
   Sr #	read SPR #\n\
   Sw #v write v to SPR #\n\
   t	print backtrace\n\
-  x	exit monitor and recover\n\
-  X	exit monitor and don't recover\n"
+  x[z]	exit monitor and recover, turn off xmon with 'z'\n\
+  X[z]	exit monitor and don't recover, turn off xmon with 'z'\n"
 #if defined(CONFIG_PPC64) && !defined(CONFIG_PPC_BOOK3E)
 "  u	dump segment table or SLB\n"
 #elif defined(CONFIG_PPC_STD_MMU_32)
@@ -952,6 +953,8 @@ cmds(struct pt_regs *excp)
 			break;
 		case 'x':
 		case 'X':
+			if (inchar() == 'z')
+				xmon_off = 1;
 			return cmd;
 		case EOF:
 			printf(" <no input ...>\n");
@@ -3248,8 +3251,11 @@ static void xmon_init(int enable)
 static void sysrq_handle_xmon(int key)
 {
 	/* ensure xmon is enabled */
+	xmon_off = 0;
 	xmon_init(1);
 	debugger(get_irq_regs());
+	if (xmon_off)
+		xmon_init(0);
 }
 
 static struct sysrq_key_op sysrq_xmon_op = {
@@ -3266,7 +3272,7 @@ 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