linux-kernel - Re: [PATCH] acpi: fix incompatibility with mcount-based function graph tracing

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Date:   Wed, 22 Mar 2017 01:04:31 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] acpi: fix incompatibility with mcount-based function
 graph tracing

Dear Josh,


On 2017-03-21 21:44, Paul Menzel wrote:

> On 2017-03-16 14:56, Josh Poimboeuf wrote:
>> Paul Menzel reported a warning:
>> 
>>   WARNING: CPU: 0 PID: 774 at
>> /build/linux-ROBWaj/linux-4.9.13/kernel/trace/trace_functions_graph.c:233
>> ftrace_return_to_handler+0x1aa/0x1e0
>>   Bad frame pointer: expected f6919d98, received f6919db0
>>     from func acpi_pm_device_sleep_wake return to c43b6f9d
>> 
>> The warning means that function graph tracing is broken for the
>> acpi_pm_device_sleep_wake() function.  That's because the acpi 
>> Makefile
>> unconditionally sets the '-Os' gcc flag to optimize for size.  That's 
>> an
>> issue because mcount-based function graph tracing is incompatible with
>> '-Os' on x86, thanks to the following gcc bug:
>> 
>>   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109
>> 
>> I have another patch pending which will ensure that mcount-based
>> function graph tracing is never used with CONFIG_CC_OPTIMIZE_FOR_SIZE 
>> on
>> x86.
>> 
>> But this patch is needed in addition to that one because the ACPI
>> Makefile overrides that config option for no apparent reason.  It has
>> had this flag since the beginning of git history, and there's no 
>> related
>> comment, so I don't know why it's there.  As far as I can tell, 
>> there's
>> no reason for it to be there.  The appropriate behavior is for it to
>> honor CONFIG_CC_OPTIMIZE_FOR_{SIZE,PERFORMANCE} like the rest of the
>> kernel.
>> 
>> Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
>> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
>> ---
>>  drivers/acpi/Makefile | 1 -
>>  1 file changed, 1 deletion(-)
>> 
>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>> index a391bbc..d94f92f 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -2,7 +2,6 @@
>>  # Makefile for the Linux ACPI interpreter
>>  #
>> 
>> -ccflags-y			:= -Os
>>  ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
>> 
>>  #
> 
> I checked out Linux 4.9.16, applied your patch on top, and copied the
> Debian 4.9 Linux kernel configuration, did `make menuconfig`, disabled
> building debugging symbols, and executed `ARCH=i386 make -j40
> deb-pkg`.
> 
> I installed that package on the Lenovo X60, and the result with
> tracing enabled has improved. The system suspends without a crash.
> Unfortunately, instead of resuming when pressing the power button, it
> starts from scratch. Suspend and resume without tracing enabled works
> though.
> 
> I’ll try to collect logs, but I don’t know, if there will be any, if
> the system just resets.

The system is able to resume with `no_console_suspend` passed to Linux 
on its command line.

```
$ more /proc/cmdline
BOOT_IMAGE=/vmlinuz-4.9.16 
root=UUID=0198e82a-32df-4f18-bec0-3e08802b084d ro noisapnp 
pcie_aspm=force pcie_aspm.policy=powersave nmi_watchdog=0 iomem=relaxed 
console=t
tyS1,115200 console=tty0 no_console_suspend
```

Please tell me, what you need from my side.

> Maybe, this can be reproduced in QEMU?


Kind regards,

Paul