Commit 86b1ae38 authored by Hariprasad Nellitheertha's avatar Hariprasad Nellitheertha Committed by Linus Torvalds
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[PATCH] kdump: sysrq trigger mechanism for kexec based crashdumps

Add a sysrq-trigger mechanism for kexec based crashdumps.  Alt-Sysrq-c
triggers a kexec based crashdump.
Signed-off-by: default avatarHariprasad Nellitheertha <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 315c215c
......@@ -72,6 +72,8 @@ On all - write a character to /proc/sysrq-trigger. eg:
'b' - Will immediately reboot the system without syncing or unmounting
your disks.
'c' - Will perform a kexec reboot in order to take a crashdump.
'o' - Will shut your system off (if configured and supported).
's' - Will attempt to sync all mounted filesystems.
......@@ -122,6 +124,9 @@ useful when you want to exit a program that will not let you switch consoles.
re'B'oot is good when you're unable to shut down. But you should also 'S'ync
and 'U'mount first.
'C'rashdump can be used to manually trigger a crashdump when the system is hung.
The kernel needs to have been built with CONFIG_KEXEC enabled.
'S'ync is great when your system is locked up, it allows you to sync your
disks and will certainly lessen the chance of data loss and fscking. Note
that the sync hasn't taken place until you see the "OK" and "Done" appear
......@@ -35,6 +35,7 @@
#include <linux/spinlock.h>
#include <linux/vt_kern.h>
#include <linux/workqueue.h>
#include <linux/kexec.h>
#include <asm/ptrace.h>
......@@ -94,6 +95,21 @@ static struct sysrq_key_op sysrq_unraw_op = {
#endif /* CONFIG_VT */
/* crashdump sysrq handler */
static void sysrq_handle_crashdump(int key, struct pt_regs *pt_regs,
struct tty_struct *tty)
static struct sysrq_key_op sysrq_crashdump_op = {
.handler = sysrq_handle_crashdump,
.help_msg = "Crashdump",
.action_msg = "Trigger a crashdump",
.enable_mask = SYSRQ_ENABLE_DUMP,
/* reboot sysrq handler */
static void sysrq_handle_reboot(int key, struct pt_regs *pt_regs,
struct tty_struct *tty)
......@@ -273,8 +289,12 @@ static struct sysrq_key_op *sysrq_key_table[SYSRQ_KEY_TABLE_LENGTH] = {
it is handled specially on the sparc
and will never arrive */
/* b */ &sysrq_reboot_op,
/* c */ NULL,
/* d */ NULL,
/* c */ &sysrq_crashdump_op,
/* c */ NULL,
/* d */ NULL,
/* e */ &sysrq_term_op,
/* f */ &sysrq_moom_op,
/* g */ NULL,
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