linux-kernel - Re: [PATCH] PM: Fix crash on graph trace through x86 suspend

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Date:	Thu, 3 Mar 2016 02:34:49 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Todd Brandt <todd.e.brandt@...ux.intel.com>
Cc:	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	todd.e.brandt@...el.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	x86@...nel.org, Steven Rostedt <rostedt@...dmins.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] PM: Fix crash on graph trace through x86 suspend

On Thu, Mar 3, 2016 at 1:43 AM, Todd Brandt
<todd.e.brandt@...ux.intel.com> wrote:
> On Thu, 2016-03-03 at 01:19 +0100, Rafael J. Wysocki wrote:
>> On Thu, Mar 3, 2016 at 1:05 AM, Todd Brandt
>> <todd.e.brandt@...ux.intel.com> wrote:
>> > Pause/unpause graph tracing around do_suspend_lowlevel as it has
>> > inconsistent call/return info after it jumps to the wakeup vector.
>> > The graph trace buffer will otherwise become misaligned and
>> > may eventually crash and hang on suspend.
>> >
>> > To reproduce the issue and test the fix:
>> > Run a function_graph trace over suspend/resume and set the graph
>> > function to suspend_devices_and_enter. This consistently hangs the
>> > system without this fix.
>> >
>> > Signed-off-by: Todd Brandt <todd.e.brandt@...ux.intel.com>
>>
>> OK
>>
>> I guess we'll need that in -stable, right?
>
> Sure, it's pretty important. The new analyze_suspend features are going
> to rely pretty heavily on full graph trace of suspend (all we can do is
> standby and freeze now because of the bug). Thanks!

OK, applied, but let Steven and the x86 folks see it.

>>
>> > ---
>> >  arch/x86/kernel/acpi/sleep.c | 7 +++++++
>> >  1 file changed, 7 insertions(+)
>> >
>> > diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
>> > index d1daead..311360e 100644
>> > --- a/arch/x86/kernel/acpi/sleep.c
>> > +++ b/arch/x86/kernel/acpi/sleep.c
>> > @@ -16,6 +16,7 @@
>> >  #include <asm/cacheflush.h>
>> >  #include <asm/realmode.h>
>> >
>> > +#include <linux/ftrace.h>
>> >  #include "../../realmode/rm/wakeup.h"
>> >  #include "sleep.h"
>> >
>> > @@ -107,7 +108,13 @@ int x86_acpi_suspend_lowlevel(void)
>> >         saved_magic = 0x123456789abcdef0L;
>> >  #endif /* CONFIG_64BIT */
>> >
>> > +       /*
>> > +        * Pause/unpause graph tracing around do_suspend_lowlevel as it has
>> > +        * inconsistent call/return info after it jumps to the wakeup vector
>> > +        */
>> > +       pause_graph_tracing();
>> >         do_suspend_lowlevel();
>> > +       unpause_graph_tracing();
>> >         return 0;
>> >  }
>> >
>> > --
>> > 2.1.4
>> >
>> > --


Thanks,
Rafael