On 10/04/13 18:37, David Daney wrote:
> On 04/10/2013 02:12 AM, Wladislav Wiebe wrote:
>> From: Wladislav Wiebe <firstname.lastname@example.org>
>> Function tracing is broken due to removal of selecting FRAME_POINTER with
>> FUNCTION_TRACER as result of commit: b732d439cb43336cd6d7e804ecb2c81193ef63b0
>> Latest commit ad8c396936e328f5344e1881afde9e28d5f2045f "MIPS: Unbreak
>> function tracer for 64-bit kernel." fixes just the early startup hang,
>> but on MIPS64/CAVIUM_OCTEON2 are still random printk recursion bugs
>> which cause also Kernel hangs, especially on late startup phase when
>> network drivers get loaded. This patch enable for CAVIUM_OCTEON2/64 Bit
>> architecture -fno-omit-frame-pointer cflag when FUNCTION_TRACER get
>> enabled. This will fix random Kernel hangs with "BUG: recent printk
>> recursion!" from linux/kernel/printk.c.
>> Maybe there exist a other solution in mcount handling, since in the
>> commit message from Al Cooper is mentioned that "MIPS frame pointers are
>> generally considered to be useless because they cannot be used to unwind
>> the stack. Unfortunately the MIPS function tracing code has bugs that
>> are masked by the use of frame pointers. This commit fixes the bugs so
>> that MIPS frame pointers don't need to be enabled."
>> But this is just a solution for MIPS32 - on a symmetric multiprocessing
>> @MIPS64/CAVIUM_OCTEON2 it doesn't work properly.
> There are a couple of problems that I see with this patch:
> 1) It doesn't handle non-OCTEON2. Surely other 64-bit targets are effected
> as well
> 2) You don't say how it is broken or how this fixes it.
> 3) Function graph tracing on 3.9.0-rc6 compiled with gcc-4.7.0 works fine for
> me without this. So I see no need to clog up the make files with a rats nest
> of ifdef
well, didn't cross checked with gcc-4.7.0 (currently using gcc-4.3).
Will do so and get back if problem still visible.
> Without more information about why this is needed, I would have to say NAK.
> David Daney
>> Signed-off-by: Wladislav Wiebe <email@example.com>
>> arch/mips/Makefile | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>> diff --git a/arch/mips/Makefile b/arch/mips/Makefile
>> index 6f7978f..8befe31 100644
>> --- a/arch/mips/Makefile
>> +++ b/arch/mips/Makefile
>> @@ -119,6 +119,15 @@ cflags-$(CONFIG_SB1XXX_CORELIS) += $(call
>> cc-option,-mno-sched-prolog) \
>> +# FTrace depended compiler options, currently only needed by MIPS64/OCTEON2.
>> +ifdef CONFIG_64BIT
>> +ifdef CONFIG_CAVIUM_OCTEON2
>> +cflags-$(CONFIG_FUNCTION_TRACER) += $(call
>> # CPU-dependent compiler/assembler options for optimization.
>> cflags-$(CONFIG_CPU_R3000) += -march=r3000