Re: [PATCH 1/4] perf tools: callchain: Warn only once in empty node detection

Frederic Weisbecker
2009-08-08T01:10:14Z

On Fri, Aug 07, 2009 at 10:06:48PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Sat, Aug 08, 2009 at 02:16:22AM +0200, Frederic Weisbecker escreveu:
> > When we fill a new node that is found to be empty (sign of a bug),
> > we print a message each time that happens. Sometimes we reach thousands
> > of lines printed.
> >
> > Just warn only once in that case (and use stderr instead of stdout).
>
> Wouldn't this be better done with a macro so that the every message is
> print once instead of any fprintf_once message?

Doh! You're right...
/me slaps his face.

> I think it would even be nice to just use the same thing the kernel
> uses... WARN_ON_ONCE, and also using asm/bug.h, etc, just add it to
> tools/perf/util/include/asm, etc.
>

Ok, I'll try that.

> That way one can even forget that this is not kernel programming... :-)

Hehe :)

> - Arnaldo
>
> > Reported-by: Ingo Molnar <mingo@elte.hu>
> > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Cc: Mike Galbraith <efault@gmx.de>
> > ---
> > tools/perf/util/callchain.c | 3 ++-
> > tools/perf/util/util.h | 3 +++
> > tools/perf/util/wrapper.c | 16 ++++++++++++++++
> > 3 files changed, 21 insertions(+), 1 deletions(-)
> >
> > diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> > index 98c5627..ce0c6d4 100644
> > --- a/tools/perf/util/callchain.c
> > +++ b/tools/perf/util/callchain.c
> > @@ -13,6 +13,7 @@
> > #include <stdio.h>
> > #include <stdbool.h>
> > #include <errno.h>
> > +#include "util.h"
> >
> > #include "callchain.h"
> >
> > @@ -203,7 +204,7 @@ fill_node(struct callchain_node *node, struct ip_callchain *chain,
> > }
> > node->val_nr = chain->nr - start;
> > if (!node->val_nr)
> > - printf("Warning: empty node in callchain tree\n");
> > + fprintf_once(stderr, "Warning: empty node in callchain tree\n");
> > }
> >
> > static void
> > diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
> > index 68fe157..386ea40 100644
> > --- a/tools/perf/util/util.h
> > +++ b/tools/perf/util/util.h
> > @@ -148,6 +148,9 @@ static inline const char *skip_prefix(const char *str, const char *prefix)
> > return strncmp(str, prefix, len) ? NULL : str + len;
> > }
> >
> > +extern int fprintf_once(FILE *fp, const char *fmt, ...)
> > + __attribute__((format (printf, 2, 3)));
> > +
> > #if defined(NO_MMAP) || defined(USE_WIN32_MMAP)
> >
> > #ifndef PROT_READ
> > diff --git a/tools/perf/util/wrapper.c b/tools/perf/util/wrapper.c
> > index 4574ac2..026c87c 100644
> > --- a/tools/perf/util/wrapper.c
> > +++ b/tools/perf/util/wrapper.c
> > @@ -205,3 +205,19 @@ int xmkstemp(char *template)
> > die("Unable to create temporary file: %s", strerror(errno));
> > return fd;
> > }
> > +
> > +int fprintf_once(FILE *fp, const char *fmt, ...)
> > +{
> > + va_list args;
> > + int ret;
> > + static int once;
> > +
> > + if (once++)
> > + return 1;
> > +
> > + va_start(args, fmt);
> > + ret = vfprintf(fp, fmt, args);
> > + va_end(args);
> > +
> > + return ret;
> > +}
> > --
> > 1.6.2.3