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From: Dave Young on 6 Feb 2010 08:50
printk delay help us to capture printk messages on some unconvenient senarios,
but it is still not easy to read.

Add another sysctl variable printk_delay_per_lines to make it more readable.
We can set the lines according to screen height, then take pictures by camera.

kmesg will delay printk_delay_per_lines * printk_delay_msecs milliseconds
after every printk_delay_per_lines lines when printk_delay is enabled.

Setting the lines by proc/sysctl interface:
/proc/sys/kernel/printk_delay_per_lines

Andrew, sorry, I have not find time to cleanup the kernel.h sysctl variables.
If I'm free I will try to do it.

The value range from 1 - 100, default value is 1

Signed-off-by: Dave Young <hidave.darkstar(a)gmail.com>
---

Documentation/sysctl/kernel.txt | 9 +++++++++
include/linux/kernel.h | 1 +
kernel/printk.c | 12 +++++++++++-
kernel/sysctl.c | 9 +++++++++
4 files changed, 30 insertions(+), 1 deletions(-)

--- linux-2.6.orig/Documentation/sysctl/kernel.txt 2010-02-02 13:38:09.517495705 +0800
+++ linux-2.6/Documentation/sysctl/kernel.txt 2010-02-02 13:40:47.657480122 +0800
@@ -374,6 +374,15 @@ Value from 0 - 10000 is allowed.

==============================================================

+printk_delay_per_lines:
+
+Delay printk message every printk_delay_per_lines lines
+in printk_delay * printk_delay_per_lines milliseconds
+
+Value from 1 - 100 is allowed.
+
+==============================================================
+
randomize-va-space:

This option can be used to select the type of process address
--- linux-2.6.orig/include/linux/kernel.h 2010-02-02 13:38:09.537495564 +0800
+++ linux-2.6/include/linux/kernel.h 2010-02-02 13:40:47.657480122 +0800
@@ -246,6 +246,7 @@ extern bool printk_timed_ratelimit(unsig
unsigned int interval_msec);

extern int printk_delay_msec;
+extern int printk_delay_per_lines;

/*
* Print a one-time message (analogous to WARN_ONCE() et al):
--- linux-2.6.orig/kernel/printk.c 2010-02-02 13:39:19.446657319 +0800
+++ linux-2.6/kernel/printk.c 2010-02-02 13:40:47.660813615 +0800
@@ -656,16 +656,26 @@ static int new_text_line = 1;
static char printk_buf[1024];

int printk_delay_msec __read_mostly;
+int printk_delay_per_lines __read_mostly;

static inline void printk_delay(void)
{
if (unlikely(printk_delay_msec)) {
- int m = printk_delay_msec;
+ static int m, l;

+ if (!l)
+ l = printk_delay_per_lines;
+
+ if (--l) {
+ m += printk_delay_msec;
+ return;
+ }
+ m += printk_delay_msec;
while (m--) {
mdelay(1);
touch_nmi_watchdog();
}
+ m = 0;
}
}

--- linux-2.6.orig/kernel/sysctl.c 2010-02-02 13:38:09.507495705 +0800
+++ linux-2.6/kernel/sysctl.c 2010-02-02 13:40:47.660813615 +0800
@@ -684,6 +684,15 @@ static struct ctl_table kern_table[] = {
.extra1 = &zero,
.extra2 = &ten_thousand,
},
+ {
+ .procname = "printk_delay_per_lines",
+ .data = &printk_delay_per_lines,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &one,
+ .extra2 = &one_hundred,
+ },
#endif
{
.procname = "ngroups_max",
--
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Prev: [PATCH 1/2] printk delay for each line break instead of callback
Next: PROBLEM: iwlagn kernel 2.6.32.3 ooops