On Thu, Jun 19, 2008 at 02:50:49PM -0700, Eric W. Biederman wrote:
I withdraw the above chunk. As Eric pointed out, sys_kexec_load() is
not where the new kernel is started. That is done in kernel_kexec()
which already runs the reboot_notifier_list.
I suppose one could trust that someone with superuser permission would
not stop one partition of a multi-partitioned system in a cavalier manner.
I'm inclined to think we should run the reboot_notifier_list even in those
situations.
But definitely on some watchdog timeout event. Some kind of mechanism
should be invoked to communicate the stoppage.
agree
done
The panic() function has the panic_notifier_list for those cases where
crash_kexec() does not find a crash kernel to exec.
That leaves holes for watchdog-type events and crash_kexec().
Can you elborate on the problem with running a non-blocking scan of
the reboot_notifier_list in those situations?
What do you have in mind as a platform specific function, that would
be an improvement over the reboot_notifier_list?
My current (v2) proposed patch for using the reboot_notifier_list as
this mechanism looks like this:
(and I'm not sure if using atomic_notifier_call_chain() might be a better
alternative to raw_notifier_call_chain())
Subject: [PATCHv2] reboot-notify additions
reboot-notify additions
This patch adds scans of the "reboot_notifier_list" callback chain in
the remaining places where the kernel is being stopped and/or restarted.
Adds 2 calls to raw_notifier_call_chain() in:
crash_kexec(), emergency_restart()
Diffed against 2.6.26-rc6
Signed-off-by: Cliff Wickman <cpw@sgi.com>
---
include/linux/notifier.h | 5 +++++
kernel/kexec.c | 6 ++++++
kernel/sys.c | 7 +++++++
3 files changed, 18 insertions(+)
Index: linux/include/linux/notifier.h
===================================================================
--- linux.orig/include/linux/notifier.h
+++ linux/include/linux/notifier.h
@@ -202,6 +202,11 @@ static inline int notifier_to_errno(int
#define SYS_RESTART SYS_DOWN
#define SYS_HALT 0x0002 /* Notify of system halt */
#define SYS_POWER_OFF 0x0003 /* Notify of system power off */
+#define SYS_EMERGENCY 0x0004 /* Notify of system error/panic/oops */
+/*
+ * For the SYS_EMERGENCY case, no locks should be taken by the called-back
+ * function.
+ */
#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
Index: linux/kernel/kexec.c
===================================================================
--- linux.orig/kernel/kexec.c
+++ linux/kernel/kexec.c
@@ -1063,11 +1063,17 @@ void crash_kexec(struct pt_regs *regs)
* If the crash kernel was not located in a fixed area
* of memory the xchg(&kexec_crash_image) would be
* sufficient. But since I reuse the memory...
+ *
+ * The reboot_notifier_list uses a header for a blocking-form scan.
+ * Use a local header suitable for a non-blocking scan.
*/
locked = xchg(&kexec_lock, 1);
if (!locked) {
if (kexec_crash_image) {
struct pt_regs fixed_regs;
+ struct raw_notifier_head rh;
+ rh.head = reboot_notifier_list.head;
+ raw_notifier_call_chain(&rh, SYS_EMERGENCY, NULL);
crash_setup_regs(&fixed_regs, regs);
crash_save_vmcoreinfo();
machine_crash_shutdown(&fixed_regs);
Index: linux/kernel/sys.c
===================================================================
--- linux.orig/kernel/sys.c
+++ linux/kernel/sys.c
@@ -267,9 +267,16 @@ out_unlock:
* reboot the system. This is called when we know we are in
* trouble so this is our best effort to reboot. This is
* safe to call in interrupt context.
+ *
+ * The reboot_notifier_list uses a header for a blocking-form scan.
+ * Use a local header suitable for a non-blocking scan.
*/
void emergency_restart(void)
{
+ struct raw_notifier_head rh;
+
+ rh.head = reboot_notifier_list.head;
+ raw_notifier_call_chain(&rh, SYS_EMERGENCY, NULL);
machine_emergency_restart();
}
EXPORT_SYMBOL_GPL(emergency_restart);
--
Cliff Wickman
Silicon Graphics, Inc.
cpw@sgi.com
(651) 683-3824
--
