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RE: locking timeout error ?
- From: "Stone, Joshua I" <joshua dot i dot stone at intel dot com>
- To: "Martin Hunt" <hunt at redhat dot com>, "Badari Pulavarty" <pbadari at us dot ibm dot com>
- Cc: <systemtap at sources dot redhat dot com>
- Date: Fri, 6 Jan 2006 16:37:28 -0800
- Subject: RE: locking timeout error ?
Martin Hunt wrote:
> On Fri, 2006-01-06 at 15:25 -0800, Badari Pulavarty wrote:
>> What does this mean ?
>>
>> # stap -g topsys.stp
>> ERROR: locking timeout over variable global_syscalls_count near
>> identifier 'syscalls_count' at topsys.stp:27:2
>
> You've found a bug.
>
> If you are saving stats in a map, then trying to print them, you have
> probably hit http://sourceware.org/bugzilla/show_bug.cgi?id=2056
>
> Otherwise, can you post some source which shows what you are doing?
>
> Martin
This is in CVS: tests/testsuite/systemtap.samples/topsys.stp
In fact the problem here is that the script is *not* using stats - it's
incrementing a counter in a global array. So Badari must be running on
an SMP machine, and two threads are trying to access the array at the
same time.
A few days ago Frank checked in code to let it wait longer to attain a
lock, so you might have better luck with a newer CVS build.
I would suggest that we should convert that script to use stats, but as
Martin points out, it's also buggy right now.
Josh