Hi, On 10/04/13 18:37, David Daney wrote: > On 04/10/2013 02:12 AM, Wladislav Wiebe wrote: >> >> From: Wladislav Wiebe <wladislav.kw@xxxxxxxxx> >> >> 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. Thanks! > > Without more information about why this is needed, I would have to say NAK. > > David Daney > >> >> Signed-off-by: Wladislav Wiebe <wladislav.kw@xxxxxxxxx> >> --- >> 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) += $(call cc-option,-mno-sched-prolog) \ >> -fno-omit-frame-pointer >> >> # >> +# FTrace depended compiler options, currently only needed by MIPS64/OCTEON2. >> +# >> +ifdef CONFIG_64BIT >> +ifdef CONFIG_CAVIUM_OCTEON2 >> +cflags-$(CONFIG_FUNCTION_TRACER) += $(call cc-option,-fno-omit-frame-pointer) >> +endif >> +endif >> + >> +# >> # CPU-dependent compiler/assembler options for optimization. >> # >> cflags-$(CONFIG_CPU_R3000) += -march=r3000 >> >
