Hi all, Here is another approach to fixing tracers vs. CALLER_ADDR problem on PowerPC.
Preface for those who don't know or forgot what the problem is: Gcc frame pointers do nothing useful on PowerPC (they're harmful, actually), and thus lib/Kconfig.debug makes CONFIG_FRAME_POINTER unselectable on PPC targets, but CALLER_ADDR macros are available only with CONFIG_FRAME_POINTER, therefore tracing is completely useless on PowerPC: [...] <idle>-0 0X.h3 2us+: 0:140:R + [000] 1733:120:S mvtsd <idle>-0 0X.h3 9us+: 0 (0) <idle>-0 0X..3 72us : 0 (0) <idle>-0 0X..3 73us : 0:140:R ==> [000] 1733:120:R mvtsd While it should look like this: [...] <idle>-0 0X.h3 2us+: 0:140:R + [000] 1740:120:S mvtsd <idle>-0 0X.h3 9us+: hrtimer_wakeup (__run_hrtimer) <idle>-0 0X..3 87us : cpu_idle (__got2_end) <idle>-0 0X..3 89us : 0:140:R ==> [000] 1740:120:R mvtsd I've tried to fix the issue via expanding the #ifdef in the ftrace.h: http://lkml.org/lkml/2009/1/31/141 Then Steven Rostedt suggested to implement something more generic, i.e. HAVE_NORMAL_FRAME_POINTERS Kconfig symbol. I found a way to solve the problem w/o additional symbols, but with some Makefile magic (http://lkml.org/lkml/2009/2/4/273). But because of top-level Makefile issues on other arches (http://lkml.org/lkml/2009/2/14/89) I had to abandon the approach. So, this patch set combines Steven Rostedt's idea and a small Makefile change, so that now only top-level Makefile has to know about the new symbol, and the rest of the kernel can stay with using CONFIG_FRAME_POINTER. -- Anton Vorontsov email: cbouatmai...@gmail.com irc://irc.freenode.net/bd2 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
