From: Mathieu Desnoyers <compudj@krystal.dyndns.org>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Martin Bligh <mbligh@google.com>,
"Frank Ch. Eigler" <fche@redhat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
prasanna@in.ibm.com, Andrew Morton <akpm@osdl.org>,
Ingo Molnar <mingo@elte.hu>, Paul Mundt <lethal@linux-sh.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Jes Sorensen <jes@sgi.com>, Tom Zanussi <zanussi@us.ibm.com>,
Richard J Moore <richardj_moore@uk.ibm.com>,
Michel Dagenais <michel.dagenais@polymtl.ca>,
Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
William Cohen <wcohen@redhat.com>,
ltt-dev@shafik.org, systemtap@sources.redhat.com,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] Linux Kernel Markers 0.7 for 2.6.17 (with type checking!)
Date: Fri, 22 Sep 2006 15:38:00 -0000 [thread overview]
Message-ID: <20060922152737.GA30668@Krystal> (raw)
In-Reply-To: <45135FA0.1030403@goop.org>
* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> Mathieu Desnoyers wrote:
> >* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> >
> >>Mathieu Desnoyers wrote:
> >>
> >>>#define MARK_SYM(name) \
> >>> do { \
> >>> __label__ here; \
> >>> volatile static void *__mark_kprobe_##name \
> >>> asm (MARK_CALL_PREFIX#name) \
> >>> __attribute__((unused)) = &&here; \
> >>>here: \
> >>> do { } while(0); \
> >>> } while(0)
> >>>
> >>>Which fixes the problem. Some tests showed me that the compiler does not
> >>>unroll
> >>>an otherwise unrolled loop when this specific macro is called. (test
> >>>done with
> >>>-funroll-all-loops).
> >>>
> >>Eh? I thought you wanted to avoid changing the generated code?
> >>Inhibiting loop unrolling could be a pretty large change...
> >>
> >>
> >
> >Yes, if possible. But letting gcc duplicate those symbols brings many
> >questions,
> >such as : how can we name each of them differently ? Is there any way to
> >automatically increment an "identifier" counter in assembly ?
>
> Use a section instead:
>
> struct marker {
> const char *name;
> const void *location;
> };
>
> #define MARKER_SYM(name)
> do {
> __label__ here;
> here: asm volatile(".section \".markers\"; .long %0, %1;
> .previous" : : "m" (#name), "m" (*&&here));\
> } while(0);
>
> Not a linker symbol, but it does let you find all the places containing
> a particular mark.
>
Very clever idea, as it lessens the impact on the compiler optimisations. Any
ideas about how we could fit in a list of "read" memory constraints based on a
vargs list in the macro ?
Mathieu
OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg
Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
next prev parent reply other threads:[~2006-09-22 15:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-22 0:01 Mathieu Desnoyers
[not found] ` <451331A1.3020601@goop.org>
2006-09-22 2:11 ` Mathieu Desnoyers
[not found] ` <45134539.7070305@goop.org>
2006-09-22 2:24 ` Mathieu Desnoyers
[not found] ` <45135FA0.1030403@goop.org>
2006-09-22 15:38 ` Mathieu Desnoyers [this message]
2006-09-22 2:49 ` Mathieu Desnoyers
[not found] ` <1160189237.21768.47.camel@localhost.localdomain>
2006-10-10 14:21 ` Proof of concept: Logdev with "almost-non" intrusive markers Mathieu Desnoyers
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