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

Arnaldo Carvalho de Melo
2009-08-08T01:12:11Z

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?

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.

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

- 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