From 9919a65ec532799544dfdfd6df6f994b74c12b42 Mon Sep 17 00:00:00 2001 From: Chris Phlipot Date: Thu, 28 Apr 2016 01:19:06 -0700 Subject: [PATCH] perf callchain: Fix incorrect ordering of entries The existing implementation of thread__resolve_callchain, under certain circumstances, can assemble callchain entries in the incorrect order. The callchain entries are resolved incorrectly for a sample when all of the following conditions are met: 1. callchain_param.order is set to ORDER_CALLER 2. thread__resolve_callchain_sample is able to resolve callchain entries for the sample. 3. unwind__get_entries is also able to resolve callchain entries for the sample. The fix is accomplished by reversing the order in which thread__resolve_callchain_sample and unwind__get_entries are called when callchain_param.order is set to ORDER_CALLER. Unwind specific code from thread__resolve_callchain is also moved into a new static function to improve readability of the fix. How to Reproduce the Existing Bug: Modifying perf script to print call trees in the opposite order or applying the remaining patches from this series and comparing the results output from export-to-postgtresql.py are the easiest ways to see the bug, however it can still be seen in current builds using perf report. Here is how i can reproduce the bug using perf report: # perf record --call-graph=dwarf stress -c 1 -t 5 when i run this command: # perf report --call-graph=flat,0,0,callee This callchain, containing kernel (handle_irq_event, etc) and userspace samples (__libc_start_main, etc) is contained in the output, which looks correct (callee order): gen8_irq_handler handle_irq_event_percpu handle_irq_event handle_edge_irq handle_irq do_IRQ ret_from_intr __random rand 0x558f2a04dded 0x558f2a04c774 __libc_start_main 0x558f2a04dcd9 Now run this command using caller order: # perf report --call-graph=flat,0,0,caller It is expected to see the exact reverse of the above when using caller order (with "0x558f2a04dcd9" at the top and "gen8_irq_handler" at the bottom) in the output, but it is nowhere to be found. instead you see this: ret_from_intr do_IRQ handle_irq handle_edge_irq handle_irq_event handle_irq_event_percpu gen8_irq_handler 0x558f2a04dcd9 __libc_start_main 0x558f2a04c774 0x558f2a04dded rand __random Notice how internally the kernel symbols are reversed and the user space symbols are reversed, but the kernel symbols still appear above the user space symbols. if this patch is applied and perf script is re-run, you will see the expected output (with "0x558f2a04dcd9" at the top and "gen8_irq_handler" at the bottom): 0x558f2a04dcd9 __libc_start_main 0x558f2a04c774 0x558f2a04dded rand __random ret_from_intr do_IRQ handle_irq handle_edge_irq handle_irq_event handle_irq_event_percpu gen8_irq_handler Signed-off-by: Chris Phlipot Tested-by: Arnaldo Carvalho de Melo Acked-by: Jiri Olsa Cc: Adrian Hunter Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1461831551-12213-2-git-send-email-cphlipot0@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/machine.c | 56 ++++++++++++++++++++++++++++----------- 1 file changed, 41 insertions(+), 15 deletions(-) diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 8c7bf4dbd479..639a2903065e 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1817,8 +1817,6 @@ static int thread__resolve_callchain_sample(struct thread *thread, int skip_idx = -1; int first_call = 0; - callchain_cursor_reset(cursor); - if (perf_evsel__has_branch_callstack(evsel)) { err = resolve_lbr_callchain_sample(thread, cursor, sample, parent, root_al, max_stack); @@ -1929,20 +1927,12 @@ static int unwind_entry(struct unwind_entry *entry, void *arg) entry->map, entry->sym); } -int thread__resolve_callchain(struct thread *thread, - struct callchain_cursor *cursor, - struct perf_evsel *evsel, - struct perf_sample *sample, - struct symbol **parent, - struct addr_location *root_al, - int max_stack) +static int thread__resolve_callchain_unwind(struct thread *thread, + struct callchain_cursor *cursor, + struct perf_evsel *evsel, + struct perf_sample *sample, + int max_stack) { - int ret = thread__resolve_callchain_sample(thread, cursor, evsel, - sample, parent, - root_al, max_stack); - if (ret) - return ret; - /* Can we do dwarf post unwind? */ if (!((evsel->attr.sample_type & PERF_SAMPLE_REGS_USER) && (evsel->attr.sample_type & PERF_SAMPLE_STACK_USER))) @@ -1955,7 +1945,43 @@ int thread__resolve_callchain(struct thread *thread, return unwind__get_entries(unwind_entry, cursor, thread, sample, max_stack); +} +int thread__resolve_callchain(struct thread *thread, + struct callchain_cursor *cursor, + struct perf_evsel *evsel, + struct perf_sample *sample, + struct symbol **parent, + struct addr_location *root_al, + int max_stack) +{ + int ret = 0; + + callchain_cursor_reset(&callchain_cursor); + + if (callchain_param.order == ORDER_CALLEE) { + ret = thread__resolve_callchain_sample(thread, cursor, + evsel, sample, + parent, root_al, + max_stack); + if (ret) + return ret; + ret = thread__resolve_callchain_unwind(thread, cursor, + evsel, sample, + max_stack); + } else { + ret = thread__resolve_callchain_unwind(thread, cursor, + evsel, sample, + max_stack); + if (ret) + return ret; + ret = thread__resolve_callchain_sample(thread, cursor, + evsel, sample, + parent, root_al, + max_stack); + } + + return ret; } int machine__for_each_thread(struct machine *machine, -- 2.20.1