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

[Paul Menzel]

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@xxxxxxxxxxxxx>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > ---
> >  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.
>
> Iâll try to collect logs, but I donât 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