Peter, this is actually an ftrace/x86 fix (not a tracing one), do you want to take it. You can add my Acked-by as well.
-- Steve On Sat, 19 Apr 2014 15:45:46 +0800 Jiaxing Wang <wangjiax...@insigma.com.cn> wrote: > When function_graph tracer is enabled, we get stack trace like this: > > Depth Size Location (88 entries) > ----- ---- -------- > 0) 3232 0 update_curr+0xe/0x1e0 > 1) 3232 0 dump_trace+0xb5/0x1b0 > 2) 3232 0 ftrace_ops_list_func+0xe6/0x100 > 3) 3232 68 ftrace_call+0x5/0xb > 4) 3164 92 enqueue_entity+0x38/0xe20 > 5) 3072 0 return_to_handler+0x0/0xf > 6) 3072 80 save_stack_trace+0x30/0x50 > 7) 2992 0 return_to_handler+0x0/0xf > 8) 2992 28 stack_trace_call+0x119/0x340 > 9) 2964 0 return_to_handler+0x0/0xf > 10) 2964 12 enqueue_task_fair+0x47/0x7e0 > 11) 2952 0 return_to_handler+0x0/0xf > 12) 2952 16 enqueue_task+0x45/0x70 > ... ... > > The 'save_stack_trace+0x30/0x50' and 'stack_trace_call+0x119/0x340' > entries are misplaced below the ftrace_ops_list_func and ftrace_call entries, > which looks very confusing. > > And dump_stack() is also affected when function_graph tracer is enabled: > > [ 425.353391] Call Trace: > [ 425.353449] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.353496] [<c1012546>] print_context_stack+0xc6/0xd0 > [ 425.353547] [<c108ab84>] enqueue_entity+0x894/0xe60 > [ 425.353597] [<c107b4c5>] ? enqueue_task+0x45/0x70 > [ 425.353649] [<c108b159>] ? enqueue_task_fair+0x9/0x7e0 > [ 425.353694] [<c107b4c5>] ? enqueue_task+0x45/0x70 > [ 425.353743] [<c1041037>] ? prepare_ftrace_return+0x77/0xa0 > [ 425.353791] [<c108b159>] ? enqueue_task_fair+0x9/0x7e0 > [ 425.353856] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.353901] [<c10116b5>] dump_trace+0xb5/0x1b0 > [ 425.353958] [<c107b4dd>] ? enqueue_task+0x5d/0x70 > [ 425.354002] [<c107b436>] ? update_rq_clock.part.80+0x6/0x50 > [ 425.354074] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.354120] [<c1012666>] show_trace_log_lvl+0x46/0x50 > [ 425.354178] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.354222] [<c1011802>] show_stack_log_lvl+0x52/0xe0 > [ 425.354272] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.354317] [<c10126c6>] show_stack+0x26/0x50 > [ 425.354369] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.354415] [<c1643be1>] dump_stack+0x41/0x52 > [ 425.354483] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.354527] [<c108b197>] enqueue_task_fair+0x47/0x7e0 > [ 425.354576] [<c16531c1>] ftrace_graph_caller+0x19/0x19 > [ 425.354621] [<c107b4c5>] enqueue_task+0x45/0x70 > ... ... > > This happens because the functions in the route of stack_trace and > dump_stack() get function_graph traced, their return addresses on stack are > replaced by 'return_to_handler' and their real return addresses are > saved in current->ret_stack[].(Specifically, these functons include > save_stack_trace,dump_trace,print_context_stack,print_ftrace_graph_addr > in the case of stack_trace and > show_stack,show_stack_log_lvl,show_trace_log_lvl > ,dump_trace,print_context_stack,print_ftrace_graph_addr in the case of > dump_stack()). > > When dumping the stack, their 'return_to_handler' on stack are skipped > but not their corresponding current->ret_stack entries which then are matched > with other function's 'return_to_handler' on the stack and resulting the > wrong output above. > > To fix this, we can disable the profiling of dumpstack utilities. > > Signed-off-by: Jiaxing Wang <wangjiax...@insigma.com.cn> > --- > arch/x86/kernel/Makefile | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile > index f4d9600..9dd8ce4 100644 > --- a/arch/x86/kernel/Makefile > +++ b/arch/x86/kernel/Makefile > @@ -14,6 +14,9 @@ CFLAGS_REMOVE_pvclock.o = -pg > CFLAGS_REMOVE_kvmclock.o = -pg > CFLAGS_REMOVE_ftrace.o = -pg > CFLAGS_REMOVE_early_printk.o = -pg > +CFLAGS_REMOVE_dumpstack.o = -pg > +CFLAGS_REMOVE_dumpstack_32.o = -pg > +CFLAGS_REMOVE_stacktrace.o = -pg > endif > > CFLAGS_irq.o := -I$(src)/../include/asm/trace -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
