The patch titled
slow down printk during boot
has been removed from the -mm tree. Its filename was
slow-down-printk-during-boot.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: slow down printk during boot
From: Randy Dunlap <rdunlap@xxxxxxxxxxxx>
Optionally add a boot delay after each kernel printk() call, crudely
measured in milliseconds, with a maximum delay of 10 seconds per printk.
Enable CONFIG_BOOT_PRINTK_DELAY=y and then add (e.g.):
"lpj=loops_per_jiffy boot_delay=100"
to the kernel command line.
It has been useful in cases like "during boot, my machine just reboots or the
screen goes black" by slowing down printk, (and adding initcall_debug), we can
usually see the last thing that happened before the lights went out which is
usually a valuable clue.
[akpm@xxxxxxxxxxxxxxxxxxxx: not all architectures implement CONFIG_HZ]
[akpm@xxxxxxxxxxxxxxxxxxxx: fix lots of stuff]
[bunk@xxxxxxxxx: kernel/printk.c: make 2 variables static]
[heiko.carstens@xxxxxxxxxx: fix slow down printk on boot compile error]
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxx>
Signed-off-by: Dave Jones <davej@xxxxxxxxxx>
Signed-off-by: Adrian Bunk <bunk@xxxxxxxxx>
Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 5 ++
include/linux/jiffies.h | 2
init/calibrate.c | 2
kernel/printk.c | 59 ++++++++++++++++++++++++++
lib/Kconfig.debug | 18 +++++++
5 files changed, 85 insertions(+), 1 deletion(-)
diff -puN Documentation/kernel-parameters.txt~slow-down-printk-during-boot Documentation/kernel-parameters.txt
--- a/Documentation/kernel-parameters.txt~slow-down-printk-during-boot
+++ a/Documentation/kernel-parameters.txt
@@ -349,6 +349,11 @@ and is between 256 and 4096 characters.
blkmtd_bs=
blkmtd_count=
+ boot_delay= Milliseconds to delay each printk during boot.
+ Values larger than 10 seconds (10000) are changed to
+ no delay (0).
+ Format: integer
+
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
bttv.radio= Most important insmod options are available as
kernel args too.
diff -puN include/linux/jiffies.h~slow-down-printk-during-boot include/linux/jiffies.h
--- a/include/linux/jiffies.h~slow-down-printk-during-boot
+++ a/include/linux/jiffies.h
@@ -148,6 +148,8 @@ static inline u64 get_jiffies_64(void)
*/
#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
+extern unsigned long preset_lpj;
+
/*
* We want to do realistic conversions of time so we need to use the same
* values the update wall clock code uses as the jiffies size. This value
diff -puN init/calibrate.c~slow-down-printk-during-boot init/calibrate.c
--- a/init/calibrate.c~slow-down-printk-during-boot
+++ a/init/calibrate.c
@@ -10,7 +10,7 @@
#include <asm/timex.h>
-static unsigned long preset_lpj;
+unsigned long preset_lpj;
static int __init lpj_setup(char *str)
{
preset_lpj = simple_strtoul(str,NULL,0);
diff -puN kernel/printk.c~slow-down-printk-during-boot kernel/printk.c
--- a/kernel/printk.c~slow-down-printk-during-boot
+++ a/kernel/printk.c
@@ -22,6 +22,8 @@
#include <linux/tty_driver.h>
#include <linux/console.h>
#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/nmi.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/interrupt.h> /* For in_interrupt() */
@@ -162,6 +164,61 @@ out:
__setup("log_buf_len=", log_buf_len_setup);
+#ifdef CONFIG_BOOT_PRINTK_DELAY
+
+static unsigned int boot_delay; /* msecs delay after each printk during bootup */
+static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
+
+static int __init boot_delay_setup(char *str)
+{
+ unsigned long lpj;
+ unsigned long long loops_per_msec;
+
+ lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
+ loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
+
+ get_option(&str, &boot_delay);
+ if (boot_delay > 10 * 1000)
+ boot_delay = 0;
+
+ printk_delay_msec = loops_per_msec;
+ printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
+ "HZ: %d, printk_delay_msec: %llu\n",
+ boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
+ return 1;
+}
+__setup("boot_delay=", boot_delay_setup);
+
+static void boot_delay_msec(void)
+{
+ unsigned long long k;
+ unsigned long timeout;
+
+ if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
+ return;
+
+ k = (unsigned long long)printk_delay_msec * boot_delay;
+
+ timeout = jiffies + msecs_to_jiffies(boot_delay);
+ while (k) {
+ k--;
+ cpu_relax();
+ /*
+ * use (volatile) jiffies to prevent
+ * compiler reduction; loop termination via jiffies
+ * is secondary and may or may not happen.
+ */
+ if (time_after(jiffies, timeout))
+ break;
+ touch_nmi_watchdog();
+ }
+}
+#else
+static inline void boot_delay_msec(void)
+{
+}
+#endif
+
/*
* Commands to do_syslog:
*
@@ -527,6 +584,8 @@ asmlinkage int vprintk(const char *fmt,
static char printk_buf[1024];
static int log_level_unknown = 1;
+ boot_delay_msec();
+
preempt_disable();
if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
/* If a crash is occurring during printk() on this CPU,
diff -puN lib/Kconfig.debug~slow-down-printk-during-boot lib/Kconfig.debug
--- a/lib/Kconfig.debug~slow-down-printk-during-boot
+++ a/lib/Kconfig.debug
@@ -413,6 +413,24 @@ config FORCED_INLINING
become the default in the future, until then this option is there to
test gcc for this.
+config BOOT_PRINTK_DELAY
+ bool "Delay each boot printk message by N milliseconds"
+ depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
+ help
+ This build option allows you to read kernel boot messages
+ by inserting a short delay after each one. The delay is
+ specified in milliseconds on the kernel command line,
+ using "boot_delay=N".
+
+ It is likely that you would also need to use "lpj=M" to preset
+ the "loops per jiffie" value.
+ See a previous boot log for the "lpj" value to use for your
+ system, and then set "lpj=M" before setting "boot_delay=N".
+ NOTE: Using this option may adversely affect SMP systems.
+ I.e., processors other than the first one may not boot up.
+ BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
+ what it believes to be lockup conditions.
+
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
_
Patches currently in -mm which might be from rdunlap@xxxxxxxxxxxx are
origin.patch
ufs-implement-show_options.patch
documentation-add-entries-to-filesystems-00-index-for-several-untracked-files.patch
add-a-missing-00-index-file-for-documentation-vm.patch
add-a-00-index-file-to-documentation-mips.patch
add-a-00-index-file-to-documentation-sysctl.patch
add-a-00-index-file-to-documentation-telephony.patch
express-relocatability-of-kernel-on-x86_64-in-documentation.patch
express-new-elf32-mechanisms-in-documentation.patch
add-reset_devices-to-the-recommended-parameters.patch
add-recommended-section-ids-to-deviceiobooktmpl.patch
fix-make-htmldocs-build-break.patch
add-section-ids-to-documentation-docbook-filesystemstmpl.patch
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