From: Peter Zijlstra <peterz@infradead.org>
To: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: mingo@redhat.com, acme@kernel.org,
alexander.shishkin@linux.intel.com, jolsa@redhat.com,
namhyung@kernel.org, linux-kernel@vger.kernel.org,
rostedt@goodmis.org, mhiramat@kernel.org,
ananth@linux.vnet.ibm.com, naveen.n.rao@linux.vnet.ibm.com,
srikar@linux.vnet.ibm.com, oleg@redhat.com
Subject: Re: [RFC 3/4] trace_uprobe: Support SDT markers having semaphore
Date: Wed, 7 Mar 2018 09:57:05 +0100 [thread overview]
Message-ID: <20180307085705.GL25181@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <3a0f9efd-158e-08ba-ae01-38391f580133@linux.vnet.ibm.com>
On Wed, Mar 07, 2018 at 02:16:13PM +0530, Ravi Bangoria wrote:
> > W.T.H. is that called a semaphore? afaict its just a usage-counter.
>
> I totally agree with you. But it's not me who named it semaphore :)
>
> Please refer to "Semaphore Handling" section at:
> https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
>
> We can surly name it differently in the kernel code and document it
> properly in the Documents/tracing/
Yes, just because the SDT people failed their CS101 class doesn't mean
we need to perpetuate that failure. Please name it sensibly in our code.
> > Also, would it not be much better to do userspace jump-labels for this?
> > That completely avoids the dynamic branch at the SDT site.
> >
>
> Userspace jump-label is a good idea but...
>
> Semaphore logic has already became a kinda ABI now. Tools like bcc,
> gdb, systemtap etc. flip the semaphore while probing the marker.
*groan*.. maybe suggest it for the next version; it appears we're
already at SDTv3, so surely there will be a v4 too.
next prev parent reply other threads:[~2018-03-07 8:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-28 7:53 [RFC 0/4] trace_uprobe: Support SDT markers having semaphore Ravi Bangoria
2018-02-28 7:53 ` [RFC 1/4] Uprobe: Rename map_info to uprobe_map_info Ravi Bangoria
2018-02-28 12:09 ` Srikar Dronamraju
2018-03-01 5:11 ` Ravi Bangoria
2018-02-28 7:53 ` [RFC 2/4] Uprobe: Export few functions / data structures Ravi Bangoria
2018-02-28 12:24 ` Srikar Dronamraju
2018-03-01 5:25 ` Ravi Bangoria
2018-02-28 7:53 ` [RFC 3/4] trace_uprobe: Support SDT markers having semaphore Ravi Bangoria
2018-03-01 14:07 ` Masami Hiramatsu
2018-03-02 3:54 ` Ravi Bangoria
2018-03-06 11:59 ` Peter Zijlstra
2018-03-07 8:46 ` Ravi Bangoria
2018-03-07 8:57 ` Peter Zijlstra [this message]
2018-02-28 7:53 ` [RFC 4/4] trace_uprobe: Fix multiple update of same semaphores Ravi Bangoria
2018-02-28 12:06 ` [RFC 0/4] trace_uprobe: Support SDT markers having semaphore Srikar Dronamraju
2018-03-01 5:10 ` Ravi Bangoria
2018-02-28 14:25 ` Masami Hiramatsu
2018-03-01 5:32 ` Ravi Bangoria
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180307085705.GL25181@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=ananth@linux.vnet.ibm.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=naveen.n.rao@linux.vnet.ibm.com \
--cc=oleg@redhat.com \
--cc=ravi.bangoria@linux.vnet.ibm.com \
--cc=rostedt@goodmis.org \
--cc=srikar@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox