lkml.org 
[lkml]   [2008]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] markers: remove 2 exported symbols
* Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
> Mathieu Desnoyers wrote:
> > * Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
> >> __mark_empty_function() and marker_probe_cb_noarg()
> >> should not be seen by outer code. this patch remove them.
> >>
> >> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> >> ---
> >> diff --git a/include/linux/marker.h b/include/linux/marker.h
> >> index 1290653..f4d4d28 100644
> >> --- a/include/linux/marker.h
> >> +++ b/include/linux/marker.h
> >> @@ -132,12 +132,8 @@ static inline void __printf(1, 2) ___mark_check_format(const char *fmt, ...)
> >> ___mark_check_format(format, ## args); \
> >> } while (0)
> >>
> >> -extern marker_probe_func __mark_empty_function;
> >> -
> >
> > Hi Lai,
> >
> > Hrm ? Have a good look at the macro __trace_mark() in
> > include/linux/marker.h, you'll see that __mark_empty_function is
> > referenced. Have you tested this against code with declared markers ?
>
> Sorry for this,
> I have markers in my kernel test code.
> I hasn't tested this patch, for I thought it's to simple.
> I used "grep" to find "__mark_empty_function",
> but I missed one line of the results.
>
> Other problems:
> 1)
> why we need marker_probe_cb_noarg()?
> marker_probe_cb_noarg() has no performance optimization,
> and no additional format check, or other thing?
>

marker_probe_cb_noarg() does not need to setup the variable arguments,
because the format string explicitly contains the MARK_NOARGS string. So
this is a performance optimization.

> if we remove marker_probe_cb_noarg, we can remove struct marker.call also.
>
> 2)
> why we use va_list *?
> As I know, sizeof(va_list) = 4 or 8.
>

It becomes hellish when we want to pass it as parameter to another C
function, because va_list is typedef'd as an array on some
architectures, and the array gets propoted to a pointer type, which is
in turn incompatible with the array. C language mess :-( Not much we can
do about it.

Mathieu

>
> please ignore this patch.
>
> Thanks, Lai.
>
> >
> >> extern void marker_probe_cb(const struct marker *mdata,
> >> void *call_private, ...);
> >> -extern void marker_probe_cb_noarg(const struct marker *mdata,
> >> - void *call_private, ...);
> >
> > This second change is correct. marker_probe_cb is referenced by
> > __trace_mark(), but not marker_probe_cb_noarg, which is only connected
> > when non-empty format string is found by the registration function in
> > marker.c.
> >
> >>
> >> /*
> >> * Connect a probe to a marker.
> >> diff --git a/kernel/marker.c b/kernel/marker.c
> >> index 7d1faec..4440a09 100644
> >> --- a/kernel/marker.c
> >> +++ b/kernel/marker.c
> >> @@ -81,11 +81,10 @@ static struct hlist_head marker_table[MARKER_TABLE_SIZE];
> >> * though the function pointer change and the marker enabling are two distinct
> >> * operations that modifies the execution flow of preemptible code.
> >> */
> >> -void __mark_empty_function(void *probe_private, void *call_private,
> >> +static void __mark_empty_function(void *probe_private, void *call_private,
> >> const char *fmt, va_list *args)
> >> {
> >> }
> >> -EXPORT_SYMBOL_GPL(__mark_empty_function);
> >>
> >
> > Same as comment above.
> >
> >> /*
> >> * marker_probe_cb Callback that prepares the variable argument list for probes.
> >> @@ -157,7 +156,7 @@ EXPORT_SYMBOL_GPL(marker_probe_cb);
> >> *
> >> * Should be connected to markers "MARK_NOARGS".
> >> */
> >> -void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)
> >> +static void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)
> >> {
> >> va_list args; /* not initialized */
> >> char ptype;
> >> @@ -197,7 +196,6 @@ void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)
> >> }
> >> preempt_enable();
> >> }
> >> -EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
> >>
> >
> > This one is ok.
> >
> > So overall, if you could check why you have not hit any problem when
> > removing __mark_empty_function, that would be great. The only reason I
> > see is that you had no markers in your kernel test code.
> >
> > Mathieu
> >
> >> static void free_old_closure(struct rcu_head *head)
> >> {
> >>
> >>
> >>
> >
>
>

--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


\
 
 \ /
  Last update: 2008-10-08 05:55    [W:0.550 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site