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authorHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>2009-07-29 18:04:14 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-29 22:10:36 -0400
commitcab8bd3410d448279e3bd0fbf96d31db0bf770fa (patch)
tree2ad9262b2c4d10cc705c8553015caff06a29de11 /drivers/char
parentf5a55efa140f5e9c9dd0f398fef54f20cdb74ec9 (diff)
sysrq, kdump: make sysrq-c consistent
commit d6580a9f15238b87e618310c862231ae3f352d2d ("kexec: sysrq: simplify sysrq-c handler") changed the behavior of sysrq-c to unconditional dereference of NULL pointer. So in cases with CONFIG_KEXEC, where crash_kexec() was directly called from sysrq-c before, now it can be said that a step of "real oops" was inserted before starting kdump. However, in contrast to oops via SysRq-c from keyboard which results in panic due to in_interrupt(), oops via "echo c > /proc/sysrq-trigger" will not become panic unless panic_on_oops=1. It means that even if dump is properly configured to be taken on panic, the sysrq-c from proc interface might not start crashdump while the sysrq-c from keyboard can start crashdump. This confuses traditional users of kdump, i.e. people who expect sysrq-c to do common behavior in both of the keyboard and proc interface. This patch brings the keyboard and proc interface behavior of sysrq-c in line, by forcing panic_on_oops=1 before oops in sysrq-c handler. And some updates in documentation are included, to clarify that there is no longer dependency with CONFIG_KEXEC, and that now the system can just crash by sysrq-c if no dump mechanism is configured. Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp> Acked-by: Neil Horman <nhorman@tuxdriver.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Cc: Brayan Arraes <brayan@yack.com.br> Cc: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/sysrq.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 0db35857e4d8..5d7a02f63e1c 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -35,7 +35,6 @@
35#include <linux/spinlock.h> 35#include <linux/spinlock.h>
36#include <linux/vt_kern.h> 36#include <linux/vt_kern.h>
37#include <linux/workqueue.h> 37#include <linux/workqueue.h>
38#include <linux/kexec.h>
39#include <linux/hrtimer.h> 38#include <linux/hrtimer.h>
40#include <linux/oom.h> 39#include <linux/oom.h>
41 40
@@ -124,9 +123,12 @@ static struct sysrq_key_op sysrq_unraw_op = {
124static void sysrq_handle_crash(int key, struct tty_struct *tty) 123static void sysrq_handle_crash(int key, struct tty_struct *tty)
125{ 124{
126 char *killer = NULL; 125 char *killer = NULL;
126
127 panic_on_oops = 1; /* force panic */
128 wmb();
127 *killer = 1; 129 *killer = 1;
128} 130}
129static struct sysrq_key_op sysrq_crashdump_op = { 131static struct sysrq_key_op sysrq_crash_op = {
130 .handler = sysrq_handle_crash, 132 .handler = sysrq_handle_crash,
131 .help_msg = "Crash", 133 .help_msg = "Crash",
132 .action_msg = "Trigger a crash", 134 .action_msg = "Trigger a crash",
@@ -401,7 +403,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
401 */ 403 */
402 NULL, /* a */ 404 NULL, /* a */
403 &sysrq_reboot_op, /* b */ 405 &sysrq_reboot_op, /* b */
404 &sysrq_crashdump_op, /* c & ibm_emac driver debug */ 406 &sysrq_crash_op, /* c & ibm_emac driver debug */
405 &sysrq_showlocks_op, /* d */ 407 &sysrq_showlocks_op, /* d */
406 &sysrq_term_op, /* e */ 408 &sysrq_term_op, /* e */
407 &sysrq_moom_op, /* f */ 409 &sysrq_moom_op, /* f */