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Re: [PATCH] Linux Kernel Markers 0.7 for 2.6.17 (with type checking!)
- From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- To: Jeremy Fitzhardinge <jeremy at goop dot org>
- Cc: Martin Bligh <mbligh at google dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, prasanna at in dot ibm dot com, Andrew Morton <akpm at osdl dot org>, Ingo Molnar <mingo at elte dot hu>, Paul Mundt <lethal at linux-sh dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, Jes Sorensen <jes at sgi dot com>, Tom Zanussi <zanussi at us dot ibm dot com>, Richard J Moore <richardj_moore at uk dot ibm dot com>, Michel Dagenais <michel dot dagenais at polymtl dot ca>, Christoph Hellwig <hch at infradead dot org>, Greg Kroah-Hartman <gregkh at suse dot de>, Thomas Gleixner <tglx at linutronix dot de>, William Cohen <wcohen at redhat dot com>, ltt-dev at shafik dot org, systemtap at sources dot redhat dot com, Alan Cox <alan at lxorguk dot ukuu dot org dot uk>
- Date: Thu, 21 Sep 2006 22:01:19 -0400
- Subject: Re: [PATCH] Linux Kernel Markers 0.7 for 2.6.17 (with type checking!)
- References: <20060921232024.GA16155@Krystal> <451331A1.3020601@goop.org>
* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> Mathieu Desnoyers wrote:
> >+#ifdef CONFIG_MARK_SYMBOL
> >+#define MARK_SYM(name) \
> >+ do { \
> >+ __label__ here; \
> >+ here: asm volatile \
> >+ (MARK_KPROBE_PREFIX#name " = %0" : : "m" (*&&here));
> >\
> >+ } while(0)
> >+#else
> >+#define MARK_SYM(name)
> >+#endif
>
> BTW, this won't work if you put the MARK_SYM in a loop which gcc
> unrolls; you'll only get the mark in the last unrolled iteration
> (because the symbol assignments will override each other).
>
> Do make this work properly, you really need to put the mark entries into
> a separate section, so that if gcc duplicates the code, you get
> duplicated markers too.
>
Good point, I will change it to :
#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).
Regards,
Mathieu
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