Dear Josh,
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.
I’ll try to collect logs, but I don’t know, if there will be any, if the
system just resets.
Maybe, this can be reproduced in QEMU?
Kind regards,
Paul
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