From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Menzel Subject: Re: [PATCH] acpi: fix incompatibility with mcount-based function graph tracing Date: Tue, 21 Mar 2017 21:44:03 +0100 Message-ID: References: <6559f36c6c6cdc2552b0bccf31de967367aa790d.1489672478.git.jpoimboe@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <6559f36c6c6cdc2552b0bccf31de967367aa790d.1489672478.git.jpoimboe@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Josh Poimboeuf Cc: "Rafael J . Wysocki" , Len Brown , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt , Ingo Molnar List-Id: linux-acpi@vger.kernel.org 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 > Signed-off-by: Josh Poimboeuf > --- > 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