[Bug tapsets/13330] New: Support TRACE_SYSTEM for tracepoints

[Bug tapsets/13330] New: Support TRACE_SYSTEM for tracepoints

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13330

             Bug #: 13330
           Summary: Support TRACE_SYSTEM for tracepoints
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap@sourceware.org
        ReportedBy: jistone@redhat.com
    Classification: Unclassified


Kernel tracepoints have a TRACE_SYSTEM which describes a sort of namespace for
the probe points. e.g. skb, net, napi, scsi:

$ perf list tracepoint | head
  skb:kfree_skb                                      [Tracepoint event]
  skb:consume_skb                                    [Tracepoint event]
  skb:skb_copy_datagram_iovec                        [Tracepoint event]
  net:net_dev_xmit                                   [Tracepoint event]
  net:net_dev_queue                                  [Tracepoint event]
  net:netif_receive_skb                              [Tracepoint event]
  net:netif_rx                                       [Tracepoint event]
  napi:napi_poll                                     [Tracepoint event]
  scsi:scsi_dispatch_cmd_start                       [Tracepoint event]
  scsi:scsi_dispatch_cmd_error                       [Tracepoint event]

We could add support for this in a couple of ways.  One is to make a new
context string, perhaps $$system.  We could also introduce this into the probe
syntax for selecting tracepoints.

  current syntax:  kernel.trace("NAME")

  new syntax:  kernel.trace("SYSTEM:NAME")
  or perhaps:  kernel.system("SYSTEM").trace("NAME")

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[Bug tapsets/13330] Support TRACE_SYSTEM for tracepoints

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=13330

Jonathan Lebon <jlebon at redhat dot com> changed:

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

--- Comment #1 from Jonathan Lebon <jlebon at redhat dot com> ---
*** Bug 14884 has been marked as a duplicate of this bug. ***

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[Bug tapsets/13330] Support TRACE_SYSTEM for tracepoints

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=13330

Jonathan Lebon <jlebon at redhat dot com> changed:

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

--- Comment #2 from Jonathan Lebon <jlebon at redhat dot com> ---
Added support for TRACE_SYSTEM in branch jlebon/trace_system:

$ stap -l 'kernel.trace("*")' | head
kernel.trace("9p:9p_client_req")
kernel.trace("9p:9p_client_res")
kernel.trace("9p:9p_protocol_dump")
kernel.trace("asoc:snd_soc_bias_level_done")
kernel.trace("asoc:snd_soc_bias_level_start")
kernel.trace("asoc:snd_soc_cache_sync")
kernel.trace("asoc:snd_soc_dapm_connected")
kernel.trace("asoc:snd_soc_dapm_done")
kernel.trace("asoc:snd_soc_dapm_input_path") 
kernel.trace("asoc:snd_soc_dapm_output_path")
$ stap -e 'probe kernel.trace("sched:sched_switch") { println($$system, ":",
$$name); exit() }'
sched:sched_switch
$ 

The old syntax is of course still supported. Because this change breaks the
value returned by pn(), the --compatible=2.6 switch can be used to disable
TRACE_SYSTEM support.

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Re: [Bug tapsets/13330] Support TRACE_SYSTEM for tracepoints

[Frank Ch. Eigler]

> --- Comment #2 from Jonathan Lebon <jlebon at redhat dot com> ---
> Added support for TRACE_SYSTEM in branch jlebon/trace_system:
> [...]

Looked the branch over briefly.  The work looks sound and useful,
thank you!

(As an OOPS style nit, presence of both a public member variable and a
public member function to compute its initial/sole value, is a bit
odd. (tracepoint_query::current_system and ::retrieve_*).  The
codebase is not exactly OOPS-pure, but if we can move toward it
slowly, that'd be good.  e.g., initialize the variable during a ctor,
or from a private: function, or ... something.  No big deal though.

- FChE

[Bug tapsets/13330] Support TRACE_SYSTEM for tracepoints

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=13330

Jonathan Lebon <jlebon at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Jonathan Lebon <jlebon at redhat dot com> ---
Merged into master (merge commit 7fc081b).

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