* Russell King <[email protected]> wrote:
> On Wed, Jan 17, 2007 at 10:13:19AM +0100, Ingo Molnar wrote:
> > we dont call the reboot notifiers during emergency reboot mainly because
> > it could be called from atomic context and reboot notifiers are a
> > blocking notifier list. But actually the kernel is often perfectly
> > reschedulable in this stage, so we could as well process the
> > reboot_notifier_list.
>
> My experience has been that when there has been the need to use this
> facility, the kernel hasn't been reschedulable. [...]
this decision is totally automatic - so if your situation happens and
the kernel isnt reschedulable, then the notifier chain wont be called
and nothing changes from your perspective. Hm, perhaps this should be
dependent on CONFIG_PREEMPT, to make sure preempt_count() is reliable?
but from my perspective this patch fixes a real regression.
updated patch attached below.
Ingo
-------------------->
Subject: [patch] call reboot notifier list when doing an emergency reboot
From: Ingo Molnar <[email protected]>
my laptop does not reboot unless the shutdown notifiers are called
first. So the following command, which i use as a fast way to reboot
into a new kernel:
echo b > /proc/sysrq-trigger
just hangs indefinitely after the kernel prints "System rebooting".
the thing is, that the kernel is actually reschedulable in this stage,
so we could as well process the reboot_notifier_list. (furthermore,
on -rt kernels this place is preemptable even during SysRq-b)
So just process the reboot notifier list if we are preemptable. This
will shut disk caches and chipsets off.
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sys.c | 10 ++++++++++
1 file changed, 10 insertions(+)
Index: linux/kernel/sys.c
===================================================================
--- linux.orig/kernel/sys.c
+++ linux/kernel/sys.c
@@ -29,6 +29,7 @@
#include <linux/signal.h>
#include <linux/cn_proc.h>
#include <linux/getcpu.h>
+#include <linux/hardirq.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
@@ -710,6 +711,15 @@ out_unlock:
*/
void emergency_restart(void)
{
+ /*
+ * Call the notifier chain if we are not in an
+ * atomic context:
+ */
+#ifdef CONFIG_PREEMPT
+ if (!in_atomic() && !irqs_disabled())
+ blocking_notifier_call_chain(&reboot_notifier_list,
+ SYS_RESTART, NULL);
+#endif
machine_emergency_restart();
}
EXPORT_SYMBOL_GPL(emergency_restart);
-
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