[Impact]
kernel selftest ftrace will fail with:
[42] Register/unregister many kprobe events [FAIL]
[Test case]
Run that selftest with:
cd tools/testing/selftests/ftrace/
sudo make run_tests
[Regression potential]
The suggested fix only change the test, not the ftrace code. From the nature of the test, the change would hardly prevent us from detecting other hard failures besides that we do not return EEXIST currently for duplicate probes.
=============================================
Issue found on c4.large with 5.0.0-1027.30-aws
Test failed with:
[42] Register/unregister many kprobe events [FAIL]
selftests: ftrace: ftracetest
========================================
=== Ftrace unit tests ===
[1] Basic trace file check [PASS]
[2] Basic test for tracers [PASS]
[3] Basic trace clock test [PASS]
[4] Basic event tracing check [PASS]
[5] Change the ringbuffer size [PASS]
[6] Snapshot and tracing setting [PASS]
[7] trace_pipe and trace_marker [PASS]
[8] Generic dynamic event - add/remove kprobe events [PASS]
[9] Generic dynamic event - add/remove synthetic events [PASS]
[10] Generic dynamic event - selective clear (compatibility) [PASS]
[11] Generic dynamic event - generic clear event [PASS]
[12] event tracing - enable/disable with event level files [PASS]
[13] event tracing - restricts events based on pid [PASS]
[14] event tracing - enable/disable with subsystem level files [PASS]
[15] event tracing - enable/disable with top level files [PASS]
[16] Test trace_printk from module [UNRESOLVED]
[17] ftrace - function graph filters with stack tracer [PASS]
[18] ftrace - function graph filters [PASS]
[19] ftrace - function pid filters [PASS]
[20] ftrace - stacktrace filter command [PASS]
[21] ftrace - function trace with cpumask [PASS]
[22] ftrace - test for function event triggers [PASS]
[23] ftrace - function trace on module [UNRESOLVED]
[24] ftrace - function profiling [PASS]
[25] ftrace - function profiler with function tracing [PASS]
[26] ftrace - test reading of set_ftrace_filter [PASS]
[27] ftrace - test for function traceon/off triggers [PASS]
[28] Test creation and deletion of trace instances while setting an event [PASS]
[29] Test creation and deletion of trace instances [PASS]
[30] Kprobe dynamic event - adding and removing [PASS]
[31] Kprobe dynamic event - busy event check [PASS]
[32] Kprobe dynamic event with arguments [PASS]
[33] Kprobe event with comm arguments [PASS]
[34] Kprobe event string type argument [PASS]
[35] Kprobe event symbol argument [PASS]
[36] Kprobe event argument syntax [PASS]
[37] Kprobes event arguments with types [PASS]
[38] Kprobe event auto/manual naming [PASS]
[39] Kprobe dynamic event with function tracer [PASS]
[40] Kretprobe dynamic event with arguments [PASS]
[41] Kretprobe dynamic event with maxactive [PASS]
[42] Register/unregister many kprobe events [FAIL]
[43] Kprobe dynamic event - adding and removing [PASS]
[44] test for the preemptirqsoff tracer [UNSUPPORTED]
[45] Test wakeup tracer [PASS]
[46] Test wakeup RT tracer [PASS]
[47] event trigger - test extended error support [PASS]
[48] event trigger - test field variable support [PASS]
[49] event trigger - test multiple actions on hist trigger [PASS]
[50] event trigger - test inter-event histogram trigger onmatch action [PASS]
[51] event trigger - test inter-event histogram trigger onmatch-onmax action [PASS]
[52] event trigger - test inter-event histogram trigger onmax action [PASS]
[53] event trigger - test synthetic_events syntax parser [PASS]
[54] event trigger - test event enable/disable trigger [PASS]
[55] event trigger - test trigger filter [PASS]
[56] event trigger - test histogram modifiers [PASS]
[57] event trigger - test multiple histogram triggers [PASS]
[58] event trigger - test snapshot-trigger [PASS]
[59] event trigger - test stacktrace-trigger [PASS]
[60] trace_marker trigger - test snapshot trigger [PASS]
[61] trace_marker trigger - test histogram with synthetic event against kernel event [PASS]
[62] trace_marker trigger - test histogram with synthetic event [PASS]
[63] event trigger - test traceon/off trigger [PASS]
[64] (instance) Basic test for tracers [PASS]
[65] (instance) Basic trace clock test [PASS]
[66] (instance) Change the ringbuffer size [PASS]
[67] (instance) Snapshot and tracing setting [PASS]
[68] (instance) trace_pipe and trace_marker [PASS]
[69] (instance) event tracing - enable/disable with event level files [PASS]
[70] (instance) event tracing - restricts events based on pid [PASS]
[71] (instance) event tracing - enable/disable with subsystem level files [PASS]
[72] (instance) ftrace - stacktrace filter command [PASS]
[73] (instance) ftrace - test for function event triggers [PASS]
[74] (instance) ftrace - test for function traceon/off triggers [PASS]
[75] (instance) event trigger - test event enable/disable trigger [PASS]
[76] (instance) event trigger - test trigger filter [PASS]
[77] (instance) event trigger - test histogram modifiers [PASS]
[78] (instance) event trigger - test multiple histogram triggers [PASS]
[79] (instance) trace_marker trigger - test snapshot trigger [PASS]
# of passed: 75
# of failed: 1
# of unresolved: 2
# of untested: 0
# of unsupported: 1
# of xfailed: 0
# of undefined(test bug): 0
not ok 1..1 selftests: ftrace: ftracetest [FAIL]
For reference, there was once an issue for this particular test on 5.0 kernel, bug 1840750