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authorDave Young <hidave.darkstar@gmail.com>2009-09-23 03:43:33 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 18:39:28 +0400
commitaf91322ef3f29ae4114e736e2a72e28b4d619cf9 (patch)
treedebba08531c7dd78b90b5d8f2c03f6bf7c9e7877 /kernel/printk.c
parent3a3b6ed2235f2f619889dd6096e24b6d93bf3339 (diff)
downloadlinux-af91322ef3f29ae4114e736e2a72e28b4d619cf9.tar.xz
printk: add printk_delay to make messages readable for some scenarios
When syslog is not possible, at the same time there's no serial/net console available, it will be hard to read the printk messages. For example oops/panic/warning messages in shutdown phase. Add a printk delay feature, we can make each printk message delay some milliseconds. Setting the delay by proc/sysctl interface: /proc/sys/kernel/printk_delay The value range from 0 - 10000, default value is 0 [akpm@linux-foundation.org: fix a few things] Signed-off-by: Dave Young <hidave.darkstar@gmail.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/printk.c')
-rw-r--r--kernel/printk.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index 932ea21feb18..f38b07f78a4e 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -653,6 +653,20 @@ static int recursion_bug;
static int new_text_line = 1;
static char printk_buf[1024];
+int printk_delay_msec __read_mostly;
+
+static inline void printk_delay(void)
+{
+ if (unlikely(printk_delay_msec)) {
+ int m = printk_delay_msec;
+
+ while (m--) {
+ mdelay(1);
+ touch_nmi_watchdog();
+ }
+ }
+}
+
asmlinkage int vprintk(const char *fmt, va_list args)
{
int printed_len = 0;
@@ -662,6 +676,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
char *p;
boot_delay_msec();
+ printk_delay();
preempt_disable();
/* This stops the holder of console_sem just where we want him */