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
--
1.8.3.2
--
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/
