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    SubjectRe: [RFC 0/4] trace_uprobe: Support SDT markers having semaphore
    * Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> [2018-02-28 13:23:41]:

    > # readelf -n ./tick
    > Provider: tick
    > Name: loop2
    > ... Semaphore: 0x0000000010020036
    >
    > # readelf -SW ./tick | grep probes
    > [25] .probes PROGBITS 0000000010020034 010034
    >
    >
    > Semaphore offset is 0x10036. I don't have educated 'perf probe'
    > about semaphore. So instead of using 'perf probe' command, I'm
    > manually adding entry in the <tracefs>/uprobe_events file.
    > Special char * denotes semaphore offset.
    >
    >
    > # echo "p:sdt_tick/loop2 /tmp/tick:0x6e4 *0x10036" > uprobe_events
    >
    > # perf stat -e sdt_tick:loop2 -- /tmp/tick
    > hi: 0
    > hi: 1
    > hi: 2
    > hi: 3
    > ^C
    > Performance counter stats for '/tmp/tick':
    > 4 sdt_tick:loop2
    > 3.359047827 seconds time elapsed
    >
    >
    > Feedback?
    >
    > TODO:
    > - Educate perf tool about semaphore.
    >

    Is it possible to extend perf buildcache with a new option to work with
    semaphore?

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