[Bug runtime/17091] New: pr16806.exp sometimes hangs on RHEL6

[Bug runtime/17091] New: pr16806.exp sometimes hangs on RHEL6

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17091

            Bug ID: 17091
           Summary: pr16806.exp sometimes hangs on RHEL6
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: jlebon at redhat dot com

This is related to PR16806 and possibly PR17027. It seems like the RHEL6 kernel
doesn't like the pr16806.exp testcase:

$ # Create modloop.ko and causes stap to load uprobes module
$ stap -m modloop -e 'probe process("./loop").function("ibar") {
println("entered ibar"); exit() }' -c /bin/true

$ # Repeat this staprun command multiple times until it hangs (takes ~8 runs
here)
$ staprun modloop.ko -c "timeout 1 ./loop"

On dmesg, we get the following after a while:

INFO: task stapio:12563 blocked for more than 120 seconds.
      Not tainted 2.6.32-431.20.3.el6.i686 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
stapio        D 00000002     0 12563   6814 0x00000080
 f338daa0 00000086 00000001 00000002 cae0873c f48fcacc 00000000 00009b4e
 00000000 f66f6900 000002d0 00000001 000002d0 c0b6b700 c0b6b700 f338dd48
 c0b6b700 c0b67064 c0b6b700 f338dd48 ef90c000 c0870720 00000000 c0441cca
Call Trace:
 [<c0441cca>] ? check_preempt_curr+0x5a/0x70
 [<c0450575>] ? try_to_wake_up+0x205/0x3a0
 [<c060b813>] ? rwsem_wake+0x53/0x120
 [<c047da6b>] ? prepare_to_wait+0x5b/0x60
 [<f8628575>] ? __unregister_uprobe+0x1f5/0x220 [uprobes]
 [<c047d750>] ? autoremove_wake_function+0x0/0x40
 [<fb235fcb>] ? _stp_cleanup_and_exit+0x17b/0x300 [modloop]
 [<c0470c96>] ? group_send_sig_info+0x46/0x60
 [<fb237a30>] ? _stp_ctl_write_cmd+0x120/0xce0 [modloop]
 [<c05bfe27>] ? selinux_file_permission+0xe7/0x130
 [<c05b4cec>] ? security_file_permission+0xc/0x10
 [<c0536c56>] ? rw_verify_area+0x66/0xe0
 [<fb237910>] ? _stp_ctl_write_cmd+0x0/0xce0 [modloop]
 [<c0536d70>] ? vfs_write+0xa0/0x190
 [<c05376f1>] ? sys_write+0x41/0x70
 [<c08606e4>] ? syscall_call+0x7/0xb

It seems like the __unregister_uprobe() call is hanging for some reason.

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[Bug runtime/17091] pr16806.exp sometimes hangs on RHEL6

[mcermak at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17091

Martin Cermak <mcermak at redhat dot com> changed:

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                 CC|                            |mcermak at redhat dot com

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[Bug runtime/17091] pr16806.exp sometimes hangs on RHEL6

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17091

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |fche at redhat dot com

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