ftrace:test.d--ftrace--func_hotplug.tc from ubuntu_kselftests_ftrace failed on O-azure

[Po-Hsu Lin]

Issue found on O-azure-6.11.0-1003.3

 Running './ftracetest -v test.d/ftrace/func_hotplug.tc'
 === Ftrace unit tests ===
 [1] ftrace - function trace across cpu hotplug [FAIL]
 execute: /home/azure/autotest/client/tmp/ubuntu_kselftests_ftrace/src/linux/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc
 + checkreq /home/azure/autotest/client/tmp/ubuntu_kselftests_ftrace/src/linux/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc
 + grep ^#[ \t]*requires: /home/azure/autotest/client/tmp/ubuntu_kselftests_ftrace/src/linux/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc
 + cut -f2- -d:
 + requires= function:tracer
 + eval check_requires function:tracer
 + check_requires function:tracer
 + p=function:tracer
 + r=function:tracer
 + t=function
 + [ function:tracer != function:tracer ]
 + [ function != function:tracer ]
 + grep -wq function available_tracers
 + initialize_ftrace
 + disable_tracing
 + echo 0
 + reset_tracer
 + echo nop
 + reset_trigger
 + [ -d events/synthetic ]
 + reset_trigger_file events/alarmtimer/alarmtimer_cancel/trigger events/alarmtimer/alarmtimer_fired/trigger ...
 + read line
 + grep -H :on[^:]*( events/alarmtimer/alarmtimer_cancel/trigger events/alarmtimer/alarmtimer_fired/trigger ...
 + read line
 + grep -Hv ^# events/alarmtimer/alarmtimer_cancel/trigger events/alarmtimer/alarmtimer_fired/trigger ..
 + reset_events_filter
 + read line
 + grep -v ^none events/alarmtimer/alarmtimer_cancel/filter events/alarmtimer/alarmtimer_fired/filter...
 + reset_ftrace_filter
 + [ ! -f set_ftrace_filter ]
 + echo
 + grep -v ^# set_ftrace_filter
 + read t
 + disable_events
 + echo 0
 + clear_dynamic_events
 + again=1
 + stop=1
 + [ 1 -eq 1 ]
 + stop=2
 + [ 2 -gt 10 ]
 + again=2
 + grep -v ^# dynamic_events
 + read line
 + [ 2 -eq 1 ]
 + [ -f set_event_pid ]
 + echo
 + [ -f set_ftrace_pid ]
 + echo
 + [ -f set_ftrace_notrace ]
 + echo
 + [ -f set_graph_function ]
 + echo
 + tee set_graph_function set_graph_notrace

 + [ -f stack_trace_filter ]
 + echo
 + [ -f kprobe_events ]
 + echo
 + [ -f uprobe_events ]
 + echo
 + [ -f synthetic_events ]
 + echo
 + [ -f snapshot ]
 + echo 0
 + [ -f options/pause-on-trace ]
 + echo 1
 + clear_trace
 + echo
 + enable_tracing
 + echo 1
 + . /home/azure/autotest/client/tmp/ubuntu_kselftests_ftrace/src/linux/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc
 + which nproc
 /usr/bin/nproc
 + nproc
 + NP=2
 + [ 2 -eq 1 ]
 + [ -f /sys/devices/system/cpu/cpu1/online ]
 + cat /sys/devices/system/cpu/cpu1/online
 + [ 1 = 1 ]
 + cpu=/sys/devices/system/cpu/cpu1
 + break
 + [ -z /sys/devices/system/cpu/cpu1 ]
 + echo 0
 + echo
 + basename /sys/devices/system/cpu/cpu1
 + : Set cpu1 offline/online with function tracer enabled
 + echo function
 + echo 1
 + echo 0
 ./ftracetest: 38: echo: echo: I/O error

 # of passed: 0
 # of failed: 1
 # of unresolved: 0
 # of untested: 0
 # of unsupported: 0
 # of xfailed: 0
 # of undefined(test bug): 0