Messages in this thread | | | Subject | Re: [PATCH][GIT PULL] ftrace: Rename config option HAVE_C_MCOUNT_RECORD to HAVE_C_RECORDMCOUNT | From | Steven Rostedt <> | Date | Fri, 15 Oct 2010 09:40:38 -0400 |
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On Fri, 2010-10-15 at 09:38 +0200, Ingo Molnar wrote: > FYI, a recent tracing change causes this new warning on latest -tip: > > Freeing SMP alternatives: 20k freed > ftrace: allocating 14134 entries in 28 pages > ------------[ cut here ]------------ > WARNING: at kernel/trace/ftrace.c:1006 ftrace_bug+0x94/0x1f9() > Hardware name: System Product Name > Modules linked in: > Pid: 0, comm: swapper Not tainted 2.6.36-rc8-tip+ #49604 > Call Trace: > [<c102c224>] warn_slowpath_common+0x6a/0x7f > [<c10629f3>] ? ftrace_bug+0x94/0x1f9 > [<c10633d8>] ? ftrace_process_locs+0x152/0x225 > [<c102c24d>] warn_slowpath_null+0x14/0x18 > [<c10629f3>] ftrace_bug+0x94/0x1f9 > [<c1063404>] ftrace_process_locs+0x17e/0x225 > [<c10633d8>] ? ftrace_process_locs+0x152/0x225 > [<c13fd7b4>] ftrace_init+0x112/0x12a > [<c13ed7ca>] start_kernel+0x287/0x291 > [<c13ed079>] i386_start_kernel+0x79/0x7b > ---[ end trace 4eaa2a86a8e2da22 ]--- > ftrace failed to modify [<c10633d8>] ftrace_process_locs+0x152/0x225
I know exactly what happened here, and it has to be because of the C recordmcount code, because the perl version will not process a file called ftrace.o
What happened is that ftrace_process_locs() references the mcount call, and since we are adding relocations of mcount to the __mcount_loc section, we just added a place that references the call but does not actually call mcount. So we fail the check when we try to modify a caller to mcount.
I'll see if I can add a fix to that in the code.
-- Steve
> actual: b9:44:2b:00:c1 > Enabling APIC mode: Flat. Using 1 I/O APICs > enabled ExtINT on CPU#0 > > (it booted up fine after this) > > Candidates would be: > > 0fdf136: Merge branch 'tip/perf/recordmcount-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/core > cf4db25: ftrace: Rename config option HAVE_C_MCOUNT_RECORD to HAVE_C_RECORDMCOUNT > d9d572a: Merge branch 'perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing into perf/core > c28d507: ftrace: Remove duplicate code for 64 and 32 bit in recordmcount.c > 72441cb: ftrace/x86: Add support for C version of recordmcount > 81d3858: ftrace: Add C version of recordmcount compile time code > ebc8827: x86: Barf when vmalloc and kmemcheck faults happen in NMI > 3cba11d: kconfig/x86: Add HAVE_TEXT_POKE_SMP config for stop_machine dependency > 3caa375: x86: Use __stop_machine() in text_poke_smp() > 087a4eb: stopmachine: Define __stop_machine when CONFIG_STOP_MACHINE=n > fd02e6f: kprobes: Fix selftest to clear flags field for reusing probes > 0f55a2f: kprobes: Update document about irq disabled state in kprobe handler > > Config attached. > > Gut feeling suggests that it's the new in-C recordmcount code causing > this bug. > > Thanks, > > Ingo
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