Let's Cc: LAKML, and To: Russell.
Russell, any comments on this?
Without this patch we got the heartbeat's reboot_notifier called twice while
testing the recent hibernation patches, which was unexpected and produced a
kernel panic: https://lkml.org/lkml/2014/3/19/363
Instead of fixing the heartbeat LED trigger, or the hibernation code, it
seems better to fix the ARM machine_power_off, as it's not supposed to return.
On Mar 24, Sebastian Capella wrote:
quoted hunk
Add loop to prevent return from machine_power_off if
pm_power_off is null or does not halt the system.
This caused a panic during hibernation testing on Kirkwood
Openblocks A6 board.
Signed-off-by: Sebastian Capella <redacted>
Reported-by: Ezequiel Garcia <redacted>
Cc: Len Brown <redacted>
Cc: Pavel Machek <redacted>
Cc: "Rafael J. Wysocki" <redacted>
---
arch/arm/kernel/process.c | 2 ++
1 file changed, 2 insertions(+)
--
1.7.9.5
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From: Russell King - ARM Linux <hidden> Date: 2014-03-26 00:51:40
On Tue, Mar 25, 2014 at 07:45:55PM -0300, Ezequiel Garcia wrote:
Let's Cc: LAKML, and To: Russell.
Russell, any comments on this?
Without this patch we got the heartbeat's reboot_notifier called twice while
testing the recent hibernation patches, which was unexpected and produced a
kernel panic: https://lkml.org/lkml/2014/3/19/363
I don't see why we should make this change. kernel/reboot.c handles
this function returning, so other places should do too.
Even on x86, this function can return:
void machine_power_off(void)
{
machine_ops.power_off();
}
.power_off = native_machine_power_off,
static void native_machine_power_off(void)
{
if (pm_power_off) {
if (!reboot_force)
machine_shutdown();
pm_power_off();
}
/* A fallback in case there is no PM info available */
tboot_shutdown(TB_SHUTDOWN_HALT);
}
void tboot_shutdown(u32 shutdown_type)
{
void (*shutdown)(void);
if (!tboot_enabled())
return;
Therefore, I'd say... it's a bug in the hibernation code - or we probably
have many buggy architectures. I'd suggest fixing the hibernation code
rather than stuffing some workaround like an endless loop into every
architecture.
--
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
Russell,
Thanks for the reply!
On Mar 26, Russell King - ARM Linux wrote:
On Tue, Mar 25, 2014 at 07:45:55PM -0300, Ezequiel Garcia wrote:
quoted
Without this patch we got the heartbeat's reboot_notifier called twice while
testing the recent hibernation patches, which was unexpected and produced a
kernel panic: https://lkml.org/lkml/2014/3/19/363
I don't see why we should make this change. kernel/reboot.c handles
this function returning, so other places should do too.
Even on x86, this function can return:
[..]
Therefore, I'd say... it's a bug in the hibernation code - or we probably
have many buggy architectures. I'd suggest fixing the hibernation code
rather than stuffing some workaround like an endless loop into every
architecture.
Which is exactly what Sebastian did first:
https://lkml.org/lkml/2014/3/20/605
But Pavel asked to fix ARM's machine_power_off instead.
Also, looking at the other architectures, it seems this API is not well
defined: some of them have an infinite loop, some don't. So it's hard to
say the function is supposed to return or not.
--
Ezequiel Garc?a, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
From: Russell King - ARM Linux <hidden> Date: 2014-03-26 11:00:05
On Wed, Mar 26, 2014 at 07:12:27AM -0300, Ezequiel Garcia wrote:
On Mar 26, Russell King - ARM Linux wrote:
quoted
On Tue, Mar 25, 2014 at 07:45:55PM -0300, Ezequiel Garcia wrote:
quoted
Without this patch we got the heartbeat's reboot_notifier called twice while
testing the recent hibernation patches, which was unexpected and produced a
kernel panic: https://lkml.org/lkml/2014/3/19/363
I don't see why we should make this change. kernel/reboot.c handles
this function returning, so other places should do too.
Even on x86, this function can return:
[..]
quoted
Therefore, I'd say... it's a bug in the hibernation code - or we probably
have many buggy architectures. I'd suggest fixing the hibernation code
rather than stuffing some workaround like an endless loop into every
architecture.
Which is exactly what Sebastian did first:
https://lkml.org/lkml/2014/3/20/605
But Pavel asked to fix ARM's machine_power_off instead.
Also, looking at the other architectures, it seems this API is not well
defined: some of them have an infinite loop, some don't. So it's hard to
say the function is supposed to return or not.
I'm going by x86 (which I regard as definitive) and the generic power-off
kernel code (which I've looked at all the way back to 2.6.12-rc2).
The hibernation code path should really be fixed - the paths in
kernel/reboot.c have coped for 9+ with all of these platform hooks
returning, and it's only the silly switch() in the hibernation code
that doesn't use a "default" case to handle the kernel_halt() case
which is the real cause of the problem.
As you've found, calling kernel_power_off() followed by kernel_halt()
leads to bugs in drivers: this is not an architecture thing, it's partly
a hibernation code failure for doing that, and partly a driver bug for
trying to unregister something that it's already unregistered.
--
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.