Messages in this thread | | | Date | Wed, 17 Mar 2010 15:14:43 -0400 | From | Masami Hiramatsu <> | Subject | Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures |
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Mark Wielaard wrote: > On Tue, 2010-03-16 at 18:06 -0400, Masami Hiramatsu wrote: >> Support accessing members in the data structures. With this, >> perf-probe accepts data-structure members(IOW, it now accepts >> dot '.' and arrow '->' operators) as probe arguemnts. >> >> e.g. >> >> ./perf probe --add 'schedule:44 rq->curr' >> >> ./perf probe --add 'vfs_read file->f_op->read file->f_path.dentry' >> >> Note that '>' can be interpreted as redirection in command-line. > > If you find that a problem then you can do like SystemTap does and allow > '.' in place of '->'. In the code you already use the > perf_probe_arg_field ref flag only to check that the DIE gives you the > same information. So you could just drop that and use any separator. > Then you decide based on whether you see a DW_TAG_pointer_type. This > gives the user some extra flexibility by letting them not having to care > about specifying extra type information already available elsewhere.
Thanks, when designing this feature, I considered it too.
Since perf probe already support displaying source code by --line option, users will read the probed code itself and try to probe it. In that case, I think they naturally use '.' and '->' as they read (they might try to copy & paste it).
So, I think that it would be good to support both of '.' and '->' as they are used in the code, because it will not confuse users.
Thank you,
-- Masami Hiramatsu e-mail: mhiramat@redhat.com
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