Re: [PATCH 1/1] perf bench inject-buildid: Handle writen() errors

[Namhyung Kim <namhyung@kernel.org>]

Hi Arnaldo,

On Wed, Aug 25, 2021 at 9:59 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Hi Namhyung,
>
>         Please check and ack,
>
> - Arnaldo
>
> From 4e5caa5fbe6955dd26336a0b106c52b98c793f3b Mon Sep 17 00:00:00 2001
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> Date: Wed, 25 Aug 2021 11:50:37 -0300
> Subject: [PATCH 1/2] perf bench inject-buildid: Handle writen() errors
>
> The build on fedora:35 and fedora:rawhide with clang is failing with:
>
>   49    41.00 fedora:35                     : FAIL clang version 13.0.0 (Fedora 13.0.0~rc1-1.fc35)
>     bench/inject-buildid.c:351:6: error: variable 'len' set but not used [-Werror,-Wunused-but-set-variable]
>             u64 len = 0;
>                 ^
>     1 error generated.
>     make[3]: *** [/git/perf-5.14.0-rc7/tools/build/Makefile.build:139: bench] Error 2
>   50    41.11 fedora:rawhide                : FAIL clang version 13.0.0 (Fedora 13.0.0~rc1-1.fc35)
>     bench/inject-buildid.c:351:6: error: variable 'len' set but not used [-Werror,-Wunused-but-set-variable]
>             u64 len = 0;
>                 ^
>     1 error generated.
>     make[3]: *** [/git/perf-5.14.0-rc7/tools/build/Makefile.build:139: bench] Error 2
>
> That 'len' variable is not used at all, so just make sure all the
> synthesize_RECORD() routines return ssize_t to propagate the writen()
> return, as it may fail, ditch the 'ret' var and bail out if those
> routines fail.
>
> Fixes: 0bf02a0d80427f26 ("perf bench: Add build-id injection benchmark")
> Cc: Namhyung Kim <namhyung@kernel.org>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung


> ---
>  tools/perf/bench/inject-buildid.c | 52 ++++++++++++++++++-------------
>  1 file changed, 30 insertions(+), 22 deletions(-)
>
> diff --git a/tools/perf/bench/inject-buildid.c b/tools/perf/bench/inject-buildid.c
> index 55d373b75791b0e4..17672790f1231acc 100644
> --- a/tools/perf/bench/inject-buildid.c
> +++ b/tools/perf/bench/inject-buildid.c
> @@ -133,7 +133,7 @@ static u64 dso_map_addr(struct bench_dso *dso)
>         return 0x400000ULL + dso->ino * 8192ULL;
>  }
>
> -static u32 synthesize_attr(struct bench_data *data)
> +static ssize_t synthesize_attr(struct bench_data *data)
>  {
>         union perf_event event;
>
> @@ -151,7 +151,7 @@ static u32 synthesize_attr(struct bench_data *data)
>         return writen(data->input_pipe[1], &event, event.header.size);
>  }
>
> -static u32 synthesize_fork(struct bench_data *data)
> +static ssize_t synthesize_fork(struct bench_data *data)
>  {
>         union perf_event event;
>
> @@ -169,8 +169,7 @@ static u32 synthesize_fork(struct bench_data *data)
>         return writen(data->input_pipe[1], &event, event.header.size);
>  }
>
> -static u32 synthesize_mmap(struct bench_data *data, struct bench_dso *dso,
> -                          u64 timestamp)
> +static ssize_t synthesize_mmap(struct bench_data *data, struct bench_dso *dso, u64 timestamp)
>  {
>         union perf_event event;
>         size_t len = offsetof(struct perf_record_mmap2, filename);
> @@ -198,23 +197,25 @@ static u32 synthesize_mmap(struct bench_data *data, struct bench_dso *dso,
>
>         if (len > sizeof(event.mmap2)) {
>                 /* write mmap2 event first */
> -               writen(data->input_pipe[1], &event, len - bench_id_hdr_size);
> +               if (writen(data->input_pipe[1], &event, len - bench_id_hdr_size) < 0)
> +                       return -1;
>                 /* zero-fill sample id header */
>                 memset(id_hdr_ptr, 0, bench_id_hdr_size);
>                 /* put timestamp in the right position */
>                 ts_idx = (bench_id_hdr_size / sizeof(u64)) - 2;
>                 id_hdr_ptr[ts_idx] = timestamp;
> -               writen(data->input_pipe[1], id_hdr_ptr, bench_id_hdr_size);
> -       } else {
> -               ts_idx = (len / sizeof(u64)) - 2;
> -               id_hdr_ptr[ts_idx] = timestamp;
> -               writen(data->input_pipe[1], &event, len);
> +               if (writen(data->input_pipe[1], id_hdr_ptr, bench_id_hdr_size) < 0)
> +                       return -1;
> +
> +               return len;
>         }
> -       return len;
> +
> +       ts_idx = (len / sizeof(u64)) - 2;
> +       id_hdr_ptr[ts_idx] = timestamp;
> +       return writen(data->input_pipe[1], &event, len);
>  }
>
> -static u32 synthesize_sample(struct bench_data *data, struct bench_dso *dso,
> -                            u64 timestamp)
> +static ssize_t synthesize_sample(struct bench_data *data, struct bench_dso *dso, u64 timestamp)
>  {
>         union perf_event event;
>         struct perf_sample sample = {
> @@ -233,7 +234,7 @@ static u32 synthesize_sample(struct bench_data *data, struct bench_dso *dso,
>         return writen(data->input_pipe[1], &event, event.header.size);
>  }
>
> -static u32 synthesize_flush(struct bench_data *data)
> +static ssize_t synthesize_flush(struct bench_data *data)
>  {
>         struct perf_event_header header = {
>                 .size = sizeof(header),
> @@ -348,14 +349,16 @@ static int inject_build_id(struct bench_data *data, u64 *max_rss)
>         int status;
>         unsigned int i, k;
>         struct rusage rusage;
> -       u64 len = 0;
>
>         /* this makes the child to run */
>         if (perf_header__write_pipe(data->input_pipe[1]) < 0)
>                 return -1;
>
> -       len += synthesize_attr(data);
> -       len += synthesize_fork(data);
> +       if (synthesize_attr(data) < 0)
> +               return -1;
> +
> +       if (synthesize_fork(data) < 0)
> +               return -1;
>
>         for (i = 0; i < nr_mmaps; i++) {
>                 int idx = rand() % (nr_dsos - 1);
> @@ -363,13 +366,18 @@ static int inject_build_id(struct bench_data *data, u64 *max_rss)
>                 u64 timestamp = rand() % 1000000;
>
>                 pr_debug2("   [%d] injecting: %s\n", i+1, dso->name);
> -               len += synthesize_mmap(data, dso, timestamp);
> +               if (synthesize_mmap(data, dso, timestamp) < 0)
> +                       return -1;
>
> -               for (k = 0; k < nr_samples; k++)
> -                       len += synthesize_sample(data, dso, timestamp + k * 1000);
> +               for (k = 0; k < nr_samples; k++) {
> +                       if (synthesize_sample(data, dso, timestamp + k * 1000) < 0)
> +                               return -1;
> +               }
>
> -               if ((i + 1) % 10 == 0)
> -                       len += synthesize_flush(data);
> +               if ((i + 1) % 10 == 0) {
> +                       if (synthesize_flush(data) < 0)
> +                               return -1;
> +               }
>         }
>
>         /* this makes the child to finish */
> --
> 2.31.1
>