Re: [Ltt-dev] LTTng 0.10.0-pre23 (fix)

[Mathieu Desnoyers <compudj at krystal dot dyndns dot org>]

* David Smith (dsmith@redhat.com) wrote:
> Mike Mason wrote:
> > Mathieu Desnoyers wrote:
> >> * Mathieu Desnoyers (compudj@krystal.dyndns.org) wrote:
> >>> * Mathieu Desnoyers (compudj@krystal.dyndns.org) wrote:
> >>>> Hi,
> >>>>
> >>>> I just released lttng 0.10.0-pre22 for Linux 2.6.24-rc2, which adds
> >>>> support for multiple callbacks connected to a single marker. I make
> >>>> extensive use the kernel RCU mechanism so batch connexion of probes to
> >>>> different markers can be done as quickly as possible, requiring to wait
> >>>> for quiescent state only when necessary. It proves to be important when
> >>>> connecting probes on busy systems, where waiting for ~50
> >>>> synchronize_sched() could take about 1-2 minutes.
> >>>>
> >>> Actually this release is pre21, not pre22.
> >>>
> >>
> >> LTTng 0.10.0-pre23 fixes a bug in an inaccurate assumption that a
> >> function pointer is always aligned on (at least) 2 bytes boundaries.
> >> It's not on some architectures.
> > 
> > I tested your changes on x86_64 using multiple instances of the
> > probe-example code.  Everything seems to work fine.  The code itself
> > looks fine, too, though I'm no RCU expert.  The SystemTap support for
> > markers will have to change again since the register and unregister
> > interfaces have changed.  I also noticed the arm and disarm functions
> > are gone.
> 
> Systemtap has been updated to work with latest LTTNG patch
> patch-2.6.24-rc2-lttng-0.10-pre23.tar.bz2, with one exception.
> 
> Mathieu, in samples/markers/probe_example.c, you've got:
> 
> ===
> void
> probe_subsystem_eventb(void *probe_data, void *call_data,
> 	const char *format, va_list *args) __attribute__((aligned(2)));
> ===
> 
> However, when I try to compile that (on fedora 7) I get:
> 
> ===
> probe-example.c:25: error: alignment may not be specified for
> âprobe_subsystem_eventbâ
> ===
> 
> Of course removing the '__attribute__((aligned(2)))' makes it work
> correctly.  Am I missing something here?
> 

wooops! that's a leftover from a test.. it's fixed now in LTTng
0.10.0-pre27.

Thanks!

Mathieu




> -- 
> David Smith
> dsmith@redhat.com
> Red Hat
> http://www.redhat.com
> 256.217.0141 (direct)
> 256.837.0057 (fax)
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68