[Bug tapsets/16273] New: irq_handler probe doesn't work on RHEL5 kernel

[Bug tapsets/16273] New: irq_handler probe doesn't work on RHEL5 kernel

[mcermak at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16273

            Bug ID: 16273
           Summary: irq_handler probe doesn't work on RHEL5 kernel
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tapsets
          Assignee: systemtap at sourceware dot org
          Reporter: mcermak at redhat dot com

RHEL5 kernel (2.6.18-371.el5) is missing irq_handler_entry and irq_handler_exit
tracepoints making the irq_handler tapset unusable. Present irq_entry and
irq_exit tracepoints might be usable instead, but not in a straightforward way.
Affects interrupts-by-dev.stp example.

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[Bug tapsets/16273] irq_handler probe doesn't work on RHEL5 kernel

[atomlin at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16273

atomlin at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |atomlin at redhat dot com

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[Bug tapsets/16273] irq_handler probe doesn't work on RHEL5 kernel

[dsmith at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16273

David Smith <dsmith at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |dsmith at redhat dot com
         Resolution|---                         |WONTFIX

--- Comment #1 from David Smith <dsmith at redhat dot com> ---
On RHEL6 kernels, the tracepoint 'irq_handler_entry' is called from the kernel
function handle_IRQ_event(). This function exists on RHEL5 (2.6.18-371.el5
x86_64), but is on stap's blacklist (of functions unsafe to put a kprobe on).

At this point there isn't really any other workaround that I can think of to
get around the lack of the 'irq_handler_entry' tracepoint on RHEL5.

We don't guarantee that all examples work everywhere. In this case, the
interrupts-by-dev.stp uses a kernel feature that isn't supported on RHEL5, so
the example isn't supported on RHEL5. The examples testsuite on RHEL5 should
not try to run this example, since the interrupts-by-dev.meta file has a
'test_support' item that checks for the existence of the tracepoint:

   stap -l 'kernel.trace("irq_handler_entry")' 

If the testsuite is trying to run that example, we do have a failure in the
testsuite here. Otherwise there isn't anything we can do to make this example
run on RHEL5.

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