Aw: Re: Crash when recording clock_gettime

Benjamin King benjaminking at web.de
Mon Aug 28 13:19:13 UTC 2017


Hi Robert (wow, you're fast)!
 
> > My libc is custom built with frame pointers but without further modifications.
> Can you try it with system libc?
I'll try that a bit later.

> > I have not seen this with an earlier release of rr yet. Any ideas?
> If it works in rr 4.5.0 you could bisect to find the regression.
git bisect tells me that e7b00db is the first bad commit.
 
> Try recording with -n to see if this is related to syscall buffering.
No, 'rr record -n a.out' does not do anything different.

When I set RR_LOG=all:warn, then I get this for commit e7b00db:
----
rr: Saving execution to trace directory `/home/bki/.local/share/rr/a.out-39'.
[WARN signal_state_changed() errno: SUCCESS] Delivered core-dumping signal; may misrecord CLONE_CHILD_CLEARTID memory race
=== Start rr backtrace:
rr(_ZN2rr13dump_rr_stackEv+0x36)[0x7cf841]
rr(_ZN2rr15notifying_abortEv+0x51)[0x7cf806]
rr(_ZN2rr25NewlineTerminatingOstreamD1Ev+0x5c)[0x6c708e]
rr(_ZN2rr13RecordSession20signal_state_changedEPNS_10RecordTaskEPNS0_9StepStateE+0x65b)[0x6f5bcd]
rr(_ZN2rr13RecordSession11record_stepEv+0x48d)[0x6f865f]
rr[0x6efa95]
rr(_ZN2rr13RecordCommand3runERSt6vectorISsSaISsEE+0x16a)[0x6f02fa]
rr(main+0x18a)[0x7e61e1]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x10f)[0x7f42dbc74f4f]
rr[0x62ec8f]
=== End rr backtrace
Aborted (core dumped)
----

Is this what is to be expected when a tracee is crashing?

For the previous commit, there is no logging except for the "Saving execution to trace...".

> Nothing else springs to mind immediately.
I'll doublecheck with the default libc, then.


Thanks,
  Benjamin


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