[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: Hariprasad Nellitheertha <hari@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt
index f98c2e31c143e6a114f61feaef725f4422e3b028..136d817c01babb51fc8e80ba5917544a7204c5ab 100644 (file)
--- a/Documentation/sysrq.txt
+++ b/Documentation/sysrq.txt
@@ -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

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index f59f7cbd525bcd587ec799b3050aa5d8852e75f8..53b2c8fab00eabe5957f13b555c5cced8a3a3310 100644 (file)
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -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 */
 
+#ifdef CONFIG_KEXEC
+/* crashdump sysrq handler */
+static void sysrq_handle_crashdump(int key, struct pt_regs *pt_regs,
+                               struct tty_struct *tty)
+{
+       crash_kexec();
+}
+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,
+};
+#endif
+
 /* 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,
+#ifdef CONFIG_KEXEC
+/* c */ &sysrq_crashdump_op,
+#else
+/* c */        NULL,
+#endif
+/* d */ NULL,
 /* e */        &sysrq_term_op,
 /* f */        &sysrq_moom_op,
 /* g */        NULL,