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From: "me at serhei dot io" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug bpf/26109] New: bug when begin probe exits quickly
Date: Wed, 10 Jun 2020 23:32:05 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D26109

            Bug ID: 26109
           Summary: bug when begin probe exits quickly
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: bpf
          Assignee: systemtap at sourceware dot org
          Reporter: me at serhei dot io
  Target Milestone: ---

if a bpf begin probe sets exit status, the main thread will skip the pause()
call and immediately deallocate global data structures. Then the
perf_event_loop thread will run on the corrupted data and occasionally fail.
Example result is an assertion failure due count_active_cpus() running on
corrupted data.

Could change the main thread to join() instead of detach(), but then all
threads must be modified to listen for exit status including exit status fr=
om
begin thread.

I think if the begin probe was running, it wasn't correct to start the
perf_event_loop (or PERF_EVENT_IOC_ENABLE, or any of the procfs threads) in=
 the
first place, as those things logically happen after the begin probe has alr=
eady
exited. Simply clean up and exit.

--=20
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