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Subject[PATCH v4] panic: keep blinking in spite of long spin timer mode
To keep panic_timeout accuracy when running under a hypervisor, the
current implementation only spins on long time (1 second) calls to
mdelay. That brings a good effect, but the problem is the keyboard
LEDs don't blink at all on that situation.

This patch changes to call to panic_blink_enter() between every mdelay
and keeps blinking in spite of long spin timer mode.

The time to call to mdelay is now 100ms. Even this change will keep
panic_timeout accuracy enough when running under a hypervisor.

Signed-off-by: TAMUKI Shoichi <tamuki@linet.gr.jp>
---
Changes since v3:
- get rid of CONFIG_PANIC_LONGSPIN_TIMER kernel config option
Documentation/kernel-parameters.txt | 3 -
arch/arm/mach-s3c2440/mach-gta02.c | 17 ++-----
drivers/input/serio/i8042.c | 25 ++---------
include/linux/kernel.h | 2
kernel/panic.c | 58 +++++++++++---------------
5 files changed, 37 insertions(+), 68 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index fa2f098..fd8a873 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -911,9 +911,6 @@ and is between 256 and 4096 characters. It is defined in the file
controller
i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
controllers
- i8042.panicblink=
- [HW] Frequency with which keyboard LEDs should blink
- when kernel panics (default is 0.5 sec)
i8042.reset [HW] Reset the controller during init and cleanup
i8042.unlock [HW] Unlock (ignore) the keylock

diff --git a/arch/arm/mach-s3c2440/mach-gta02.c b/arch/arm/mach-s3c2440/mach-gta02.c
index 9e39faa..deaabe8 100644
--- a/arch/arm/mach-s3c2440/mach-gta02.c
+++ b/arch/arm/mach-s3c2440/mach-gta02.c
@@ -90,24 +90,17 @@
static struct pcf50633 *gta02_pcf;

/*
- * This gets called every 1ms when we paniced.
+ * This gets called frequently when we paniced.
*/

-static long gta02_panic_blink(long count)
+static long gta02_panic_blink(int state)
{
long delay = 0;
- static long last_blink;
- static char led;
+ char led;

- /* Fast blink: 200ms period. */
- if (count - last_blink < 100)
- return 0;
-
- led ^= 1;
+ led = (state) ? 1 : 0;
gpio_direction_output(GTA02_GPIO_AUX_LED, led);

- last_blink = count;
-
return delay;
}

@@ -556,7 +549,7 @@ static void gta02_poweroff(void)

static void __init gta02_machine_init(void)
{
- /* Set the panic callback to make AUX LED blink at ~5Hz. */
+ /* Set the panic callback to turn AUX LED on or off. */
panic_blink = gta02_panic_blink;

s3c_pm_init();
diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
index 6440a8f..c32d9b3 100644
--- a/drivers/input/serio/i8042.c
+++ b/drivers/input/serio/i8042.c
@@ -61,10 +61,6 @@ static bool i8042_noloop;
module_param_named(noloop, i8042_noloop, bool, 0);
MODULE_PARM_DESC(noloop, "Disable the AUX Loopback command while probing for the AUX port");

-static unsigned int i8042_blink_frequency = 500;
-module_param_named(panicblink, i8042_blink_frequency, uint, 0600);
-MODULE_PARM_DESC(panicblink, "Frequency with which keyboard LEDs should blink when kernel panics");
-
#ifdef CONFIG_X86
static bool i8042_dritek;
module_param_named(dritek, i8042_dritek, bool, 0);
@@ -1032,8 +1028,8 @@ static void i8042_controller_reset(void)


/*
- * i8042_panic_blink() will flash the keyboard LEDs and is called when
- * kernel panics. Flashing LEDs is useful for users running X who may
+ * i8042_panic_blink() will turn the keyboard LEDs on or off and is called
+ * when kernel panics. Flashing LEDs is useful for users running X who may
* not see the console and will help distingushing panics from "real"
* lockups.
*
@@ -1043,22 +1039,12 @@ static void i8042_controller_reset(void)

#define DELAY do { mdelay(1); if (++delay > 10) return delay; } while(0)

-static long i8042_panic_blink(long count)
+static long i8042_panic_blink(int state)
{
long delay = 0;
- static long last_blink;
- static char led;
-
- /*
- * We expect frequency to be about 1/2s. KDB uses about 1s.
- * Make sure they are different.
- */
- if (!i8042_blink_frequency)
- return 0;
- if (count - last_blink < i8042_blink_frequency)
- return 0;
+ char led;

- led ^= 0x01 | 0x04;
+ led = (state) ? 0x01 | 0x04 : 0;
while (i8042_read_status() & I8042_STR_IBF)
DELAY;
dbg("%02x -> i8042 (panic blink)", 0xed);
@@ -1071,7 +1057,6 @@ static long i8042_panic_blink(long count)
dbg("%02x -> i8042 (panic blink)", led);
i8042_write_data(led);
DELAY;
- last_blink = count;
return delay;
}

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 8317ec4..7d4552a 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -172,7 +172,7 @@ static inline void might_fault(void)
#endif

extern struct atomic_notifier_head panic_notifier_list;
-extern long (*panic_blink)(long time);
+extern long (*panic_blink)(int state);
NORET_TYPE void panic(const char * fmt, ...)
__attribute__ ((NORET_AND format (printf, 1, 2))) __cold;
extern void oops_enter(void);
diff --git a/kernel/panic.c b/kernel/panic.c
index 3b16cd9..3e9037a 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -24,6 +24,9 @@
#include <linux/nmi.h>
#include <linux/dmi.h>

+#define PANIC_TIMER_STEP 100
+#define PANIC_BLINK_SPD 18
+
int panic_on_oops;
static unsigned long tainted_mask;
static int pause_on_oops;
@@ -36,36 +39,15 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

-/* Returns how long it waited in ms */
-long (*panic_blink)(long time);
-EXPORT_SYMBOL(panic_blink);
-
-static void panic_blink_one_second(void)
+static long no_blink(int state)
{
- static long i = 0, end;
-
- if (panic_blink) {
- end = i + MSEC_PER_SEC;
-
- while (i < end) {
- i += panic_blink(i);
- mdelay(1);
- i++;
- }
- } else {
- /*
- * When running under a hypervisor a small mdelay may get
- * rounded up to the hypervisor timeslice. For example, with
- * a 1ms in 10ms hypervisor timeslice we might inflate a
- * mdelay(1) loop by 10x.
- *
- * If we have nothing to blink, spin on 1 second calls to
- * mdelay to avoid this.
- */
- mdelay(MSEC_PER_SEC);
- }
+ return 0;
}

+/* Returns how long it waited in ms */
+long (*panic_blink)(int state);
+EXPORT_SYMBOL(panic_blink);
+
/**
* panic - halt the system
* @fmt: The text string to print
@@ -78,7 +60,8 @@ NORET_TYPE void panic(const char * fmt, ...)
{
static char buf[1024];
va_list args;
- long i;
+ long i, i_next = 0;
+ int state = 0;

/*
* It's possible to come here directly from a panic-assertion and
@@ -117,6 +100,9 @@ NORET_TYPE void panic(const char * fmt, ...)

bust_spinlocks(0);

+ if (!panic_blink)
+ panic_blink = no_blink;
+
if (panic_timeout > 0) {
/*
* Delay timeout seconds before rebooting the machine.
@@ -124,9 +110,13 @@ NORET_TYPE void panic(const char * fmt, ...)
*/
printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);

- for (i = 0; i < panic_timeout; i++) {
+ for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
touch_nmi_watchdog();
- panic_blink_one_second();
+ if (i >= i_next) {
+ i += panic_blink(state ^= 1);
+ i_next = i + 3600 / PANIC_BLINK_SPD;
+ }
+ mdelay(PANIC_TIMER_STEP);
}
/*
* This will not be a clean reboot, with everything
@@ -152,9 +142,13 @@ NORET_TYPE void panic(const char * fmt, ...)
}
#endif
local_irq_enable();
- while (1) {
+ for (i = 0; ; i += PANIC_TIMER_STEP) {
touch_softlockup_watchdog();
- panic_blink_one_second();
+ if (i >= i_next) {
+ i += panic_blink(state ^= 1);
+ i_next = i + 3600 / PANIC_BLINK_SPD;
+ }
+ mdelay(PANIC_TIMER_STEP);
}
}


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