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staprun -c deadlocks often


systemtap-1.4-9.fc15.x86_64
kernel 2.6.38.7-30.fc15.x86_64

I'm not sure if I'm "doing it wrong", but it appears that the staprun -c
option deadlocks for me very frequently.  Not always, but at least
more often than one time in two.

Here is what I'm doing (as root):

  stap -p4 \
  -e 'probe module("ext2").statement ("*@*.c:*") { printf ("%s\n", pp()); }'

[stap command prints the module name, used below]

  staprun -o /tmp/stap -c /bin/ls /home/rjones/.systemtap/cache/44/stap_44fe38ee6f62656645948ce5d275d678_260427.ko

As I say, more often than half the time, instead of printing out a
directory listing, the staprun command will just hang.  Note that the
filesystem I'm listing is not ext2, so I don't think the probes
themselves have anything to do with it.

When it hangs, a process listing shows:

  13073 pts/4    Ss     0:00  \_ bash
  17930 pts/4    S+     0:00  |   \_ sudo staprun -o /tmp/stap -c /bin/ls /home/rjones/.systemtap/cache/44/stap_44fe38ee6f62656645948ce5d275d678_260427.ko
  17931 pts/4    Sl+    0:00  |       \_ /usr/libexec/systemtap/stapio -o /tmp/stap -c /bin/ls /home/rjones/.systemtap/cache/44/stap_44fe38ee6f62656645948ce5d275d678_260427.ko
  17932 pts/4    S+     0:00  |           \_ /usr/libexec/systemtap/stapio -o /tmp/stap -c /bin/ls /home/rjones/.systemtap/cache/44/stap_44fe38ee6f62656645948ce5d275d678_260427.ko

Note that there is no staprun process, nor any /bin/ls, but two stapio
processes have been left around.

Any ideas?  I had a look at the code in runtime/staprun/mainloop.c but
it just looks fiendishly complex ...

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
New in Fedora 11: Fedora Windows cross-compiler. Compile Windows
programs, test, and build Windows installers. Over 70 libraries supprt'd
http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw


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