Steven Rostedt (Red Hat) 70b3d6c5aa tracing: Skip more functions when doing stack tracing of events ... [ Upstream commit be54f69c26 ] # echo 1 > options/stacktrace # echo 1 > events/sched/sched_switch/enable # cat trace <idle>-0 [002] d..2 1982.525169: <stack trace> => save_stack_trace => __ftrace_trace_stack => trace_buffer_unlock_commit_regs => event_trigger_unlock_commit => trace_event_buffer_commit => trace_event_raw_event_sched_switch => __schedule => schedule => schedule_preempt_disabled => cpu_startup_entry => start_secondary The above shows that we are seeing 6 functions before ever making it to the caller of the sched_switch event. # echo stacktrace > events/sched/sched_switch/trigger # cat trace <idle>-0 [002] d..3 2146.335208: <stack trace> => trace_event_buffer_commit => trace_event_raw_event_sched_switch => __schedule => schedule => schedule_preempt_disabled => cpu_startup_entry => start_secondary The stacktrace trigger isn't as bad, because it adds its own skip to the stacktracing, but still has two events extra. One issue is that if the stacktrace passes its own "regs" then there should be no addition to the skip, as the regs will not include the functions being called. This was an issue that was fixed by commit 7717c6be69 ("tracing: Fix stacktrace skip depth in trace_buffer_unlock_commit_regs()" as adding the skip number for kprobes made the probes not have any stack at all. But since this is only an issue when regs is being used, a skip should be added if regs is NULL. Now we have: # echo 1 > options/stacktrace # echo 1 > events/sched/sched_switch/enable # cat trace <idle>-0 [000] d..2 1297.676333: <stack trace> => __schedule => schedule => schedule_preempt_disabled => cpu_startup_entry => rest_init => start_kernel => x86_64_start_reservations => x86_64_start_kernel # echo stacktrace > events/sched/sched_switch/trigger # cat trace <idle>-0 [002] d..3 1370.759745: <stack trace> => __schedule => schedule => schedule_preempt_disabled => cpu_startup_entry => start_secondary And kprobes are not touched. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2018-11-10 07:41:35 -08:00
..
blktrace.c	tracing/blktrace: Fix to allow setting same value	2018-09-09 20:04:34 +02:00
bpf_trace.c
ftrace.c	ftrace: Remove incorrect setting of glob search field	2018-02-16 20:09:47 +01:00
Kconfig
Makefile	Makefile: Mute warning for __builtin_return_address(>0) for tracing only	2016-09-30 10:18:35 +02:00
power-traces.c
ring_buffer_benchmark.c
ring_buffer.c	ring-buffer: Allow for rescheduling when removing pages	2018-09-29 03:08:52 -07:00
rpm-traces.c
trace_benchmark.c
trace_benchmark.h
trace_branch.c
trace_clock.c
trace_entries.h
trace_event_perf.c
trace_events_filter_test.h
trace_events_filter.c	tracing: Fix regex_match_front() to not over compare the test string	2018-05-16 10:06:51 +02:00
trace_events_trigger.c	tracing: Fix possible double free in event_enable_trigger_func()	2018-08-06 16:24:29 +02:00
trace_events.c	tracing: Fix converting enum's from the map in trace_event_eval_update()	2018-01-23 19:50:16 +01:00
trace_export.c
trace_functions_graph.c	tracing: Fix missing return symbol in function_graph output	2018-07-11 16:03:48 +02:00
trace_functions.c
trace_irqsoff.c
trace_kdb.c
trace_kprobe.c	tracing: Quiet gcc warning about maybe unused link variable	2018-08-06 16:24:30 +02:00
trace_mmiotrace.c
trace_nop.c
trace_output.c
trace_output.h
trace_printk.c
trace_probe.c	tracing: probeevent: Fix to support minus offset from symbol	2018-03-28 18:40:15 +02:00
trace_probe.h	tracing: probeevent: Fix to support minus offset from symbol	2018-03-28 18:40:15 +02:00
trace_sched_switch.c
trace_sched_wakeup.c
trace_selftest_dynamic.c
trace_selftest.c	ftrace: Fix selftest goto location on error	2017-09-27 11:00:16 +02:00
trace_seq.c
trace_stack.c
trace_stat.c
trace_stat.h
trace_syscalls.c
trace_uprobe.c	uprobes: Use synchronize_rcu() not synchronize_sched()	2018-09-09 20:04:34 +02:00
trace.c	tracing: Skip more functions when doing stack tracing of events	2018-11-10 07:41:35 -08:00
trace.h