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authorTom Zanussi <zanussi@kernel.org>2020-07-02 20:53:46 +0200
committerArnaldo Carvalho de Melo <acme@redhat.com>2020-07-03 13:45:38 +0200
commit2160d6c8a13e685b7b2bacbe9cd1e9600506a05f (patch)
tree8ef5aacfec71bab1efb63277809275464bd4b2e2 /tools/usb/ffs-aio-example
parenttools lib traceevent: Add API to read time information from kbuffer (diff)
downloadlinux-2160d6c8a13e685b7b2bacbe9cd1e9600506a05f.tar.xz
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tools lib traceevent: Add proper KBUFFER_TYPE_TIME_STAMP handling
Kernel commit dc4e2801d400 (ring-buffer: Redefine the unimplemented RINGBUF_TYPE_TIME_STAMP) changed the way the ring buffer timestamps work - after that commit the previously unimplemented RINGBUF_TYPE_TIME_STAMP type causes the time delta to be used as a timestamp rather than a delta to be added to the timestamp. The trace-cmd code didn't get updated to handle this, so misinterprets the event data for this case, which causes a cascade of errors, including trace-report not being able to identify synthetic (or any other) events generated by the histogram code (which uses TIME_STAMP mode). For example, the following triggers along with the trace-cmd shown cause an UNKNOWN_EVENT error and trace-cmd report crash: # echo 'wakeup_latency u64 lat pid_t pid char comm[16]' > /sys/kernel/debug/tracing/synthetic_events # echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_wakeup).trace(wakeup_latency,$wakeup_lat,next_pid,next_comm) if next_comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_switch/trigger # echo 'hist:keys=comm,pid,lat:wakeup_lat=lat:sort=lat' > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger # trace-cmd record -e wakeup_latency -e sched_wakeup -f comm==\"ping\" ping localhost -c 5 # trace-cmd report CPU 0 is empty CPU 1 is empty CPU 2 is empty CPU 3 is empty CPU 5 is empty CPU 6 is empty CPU 7 is empty cpus=8 ug! no event found for type 0 [UNKNOWN TYPE 0] ug! no event found for type 11520 Segmentation fault (core dumped) After this patch we get the correct interpretation and the events are shown properly: # trace-cmd report CPU 0 is empty CPU 1 is empty CPU 2 is empty CPU 3 is empty CPU 5 is empty CPU 6 is empty CPU 7 is empty cpus=8 <idle>-0 [004] 23284.341392: sched_wakeup: ping:12031 [120] success=1 CPU:004 <idle>-0 [004] 23284.341464: wakeup_latency: lat=58, pid=12031, comm=ping <idle>-0 [004] 23285.365303: sched_wakeup: ping:12031 [120] success=1 CPU:004 <idle>-0 [004] 23285.365382: wakeup_latency: lat=64, pid=12031, comm=ping <idle>-0 [004] 23286.389290: sched_wakeup: ping:12031 [120] success=1 CPU:004 <idle>-0 [004] 23286.389378: wakeup_latency: lat=72, pid=12031, comm=ping <idle>-0 [004] 23287.413213: sched_wakeup: ping:12031 [120] success=1 CPU:004 <idle>-0 [004] 23287.413291: wakeup_latency: lat=64, pid=12031, comm=ping Link: http://lkml.kernel.org/r/1567628224.13841.4.camel@kernel.org Link: http://lore.kernel.org/linux-trace-devel/20200625100516.365338-3-tz.stoyanov@gmail.com Signed-off-by: Tom Zanussi <zanussi@kernel.org> [ Ported from trace-cmd.git ] Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: linux-trace-devel@vger.kernel.org Link: http://lore.kernel.org/lkml/20200702185703.785094515@goodmis.org Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/usb/ffs-aio-example')
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