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powerpc/xmon: Fix an unexpected xmon on/off state change

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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 interrupt
fail to dump. So keep xmon in its original state after exit.

We have several ways to set xmon on or off.
1) by a build config CONFIG_XMON_DEFAULT.
2) by a boot cmdline with xmon or xmon=early or xmon=on to enable xmon
and xmon=off to disable xmon. This value will override that in step 1.
3) by a debugfs interface, as proposed in this patchset.
And this value can override those in step 1 and 2.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Pan Xinhui 2017-03-22 16:27:49 -03:00 committed by Michael Ellerman
parent c7e790c5f4
commit 3b5bf42b81
1 changed files with 10 additions and 7 deletions
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17
arch/powerpc/xmon/xmon.c
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@ -76,6 +76,7 @@ static int xmon_gate;
#endif /* CONFIG_SMP */
static unsigned long in_xmon __read_mostly = 0;
static int xmon_on = IS_ENABLED(CONFIG_XMON_DEFAULT);
static unsigned long adrs;
static int size = 1;
@ -3302,6 +3303,8 @@ static void sysrq_handle_xmon(int key)
/* ensure xmon is enabled */
xmon_init(1);
debugger(get_irq_regs());
if (!xmon_on)
xmon_init(0);
}
static struct sysrq_key_op sysrq_xmon_op = {
@ -3318,7 +3321,7 @@ 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)
{
@ -3326,10 +3329,12 @@ static int __init early_parse_xmon(char *p)
/* just "xmon" is equivalent to "xmon=early" */
xmon_init(1);
xmon_early = 1;
} else if (strncmp(p, "on", 2) == 0)
xmon_on = 1;
} else if (strncmp(p, "on", 2) == 0) {
xmon_init(1);
else if (strncmp(p, "off", 3) == 0)
xmon_off = 1;
xmon_on = 1;
} else if (strncmp(p, "off", 3) == 0)
xmon_on = 0;
else if (strncmp(p, "nobt", 4) == 0)
xmon_no_auto_backtrace = 1;
else
@ -3341,10 +3346,8 @@ early_param("xmon", early_parse_xmon);
void __init xmon_setup(void)
{
#ifdef CONFIG_XMON_DEFAULT
if (!xmon_off)
if (xmon_on)
xmon_init(1);
#endif
if (xmon_early)
debugger(NULL);
}