[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>

[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>
Hariprasad Nellitheertha · Linus Torvalds
1 parent 315c215c0a
Showing 2 changed files with 27 additions and 2 deletions Side-by-side Diff
Documentation/sysrq.txt
drivers/char/sysrq.c
@@ -72,6 +72,8 @@
 '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.
@@ -121,6 +123,9 @@
  
 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
@@ -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 @@
 };
 #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 @@
 		 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,
...	...	@@ -72,6 +72,8 @@
72	72	'b' - Will immediately reboot the system without syncing or unmounting
73	73	your disks.
74	74
	75	+'c' - Will perform a kexec reboot in order to take a crashdump.
	76	+
75	77	'o' - Will shut your system off (if configured and supported).
76	78
77	79	's' - Will attempt to sync all mounted filesystems.
...	...	@@ -121,6 +123,9 @@
121	123
122	124	re'B'oot is good when you're unable to shut down. But you should also 'S'ync
123	125	and 'U'mount first.
	126	+
	127	+'C'rashdump can be used to manually trigger a crashdump when the system is hung.
	128	+The kernel needs to have been built with CONFIG_KEXEC enabled.
124	129
125	130	'S'ync is great when your system is locked up, it allows you to sync your
126	131	disks and will certainly lessen the chance of data loss and fscking. Note
...	...	@@ -35,6 +35,7 @@
35	35	#include <linux/spinlock.h>
36	36	#include <linux/vt_kern.h>
37	37	#include <linux/workqueue.h>
	38	+#include <linux/kexec.h>
38	39
39	40	#include <asm/ptrace.h>
40	41
...	...	@@ -94,6 +95,21 @@
94	95	};
95	96	#endif /* CONFIG_VT */
96	97
	98	+#ifdef CONFIG_KEXEC
	99	+/* crashdump sysrq handler */
	100	+static void sysrq_handle_crashdump(int key, struct pt_regs *pt_regs,
	101	+ struct tty_struct *tty)
	102	+{
	103	+ crash_kexec();
	104	+}
	105	+static struct sysrq_key_op sysrq_crashdump_op = {
	106	+ .handler = sysrq_handle_crashdump,
	107	+ .help_msg = "Crashdump",
	108	+ .action_msg = "Trigger a crashdump",
	109	+ .enable_mask = SYSRQ_ENABLE_DUMP,
	110	+};
	111	+#endif
	112	+
97	113	/* reboot sysrq handler */
98	114	static void sysrq_handle_reboot(int key, struct pt_regs *pt_regs,
99	115	struct tty_struct *tty)
...	...	@@ -273,8 +289,12 @@
273	289	it is handled specially on the sparc
274	290	and will never arrive */
275	291	/* b */ &sysrq_reboot_op,
276		-/* c */ NULL,
277		-/* d */ NULL,
	292	+#ifdef CONFIG_KEXEC
	293	+/* c */ &sysrq_crashdump_op,
	294	+#else
	295	+/* c */ NULL,
	296	+#endif
	297	+/* d */ NULL,
278	298	/* e */ &sysrq_term_op,
279	299	/* f */ &sysrq_moom_op,
280	300	/* g */ NULL,