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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@molgen.mpg.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: All applicable <stable@vger.kernel.org>
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.