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Fri, 17 Jul 2020 06:58:48 -0700 (PDT) Date: Fri, 17 Jul 2020 21:58:38 +0800 From: Changbin Du To: Namhyung Kim Cc: Changbin Du , Jiri Olsa , Arnaldo Carvalho de Melo , Peter Zijlstra , Ingo Molnar , Steven Rostedt , linux-kernel Subject: Re: [PATCH v5 02/17] perf ftrace: add option '-F/--funcs' to list available functions Message-ID: <20200717135838.b2sch4sulsdptc6u@mail.google.com> References: <20200711124035.6513-1-changbin.du@gmail.com> <20200711124035.6513-3-changbin.du@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 13, 2020 at 10:49:40AM +0900, Namhyung Kim wrote: > Hello, > > On Sat, Jul 11, 2020 at 9:42 PM Changbin Du wrote: > > > > This adds an option '-F/--funcs' to list all available functions to trace, > > which is read from tracing file 'available_filter_functions'. > > > > $ sudo ./perf ftrace -F | head > > trace_initcall_finish_cb > > initcall_blacklisted > > do_one_initcall > > do_one_initcall > > trace_initcall_start_cb > > run_init_process > > try_to_run_init_process > > match_dev_by_label > > match_dev_by_uuid > > rootfs_init_fs_context > > > > Signed-off-by: Changbin Du > > > > --- > > v2: option name '-l/--list-functions' -> '-F/--funcs' > > --- > > tools/perf/Documentation/perf-ftrace.txt | 4 +++ > > tools/perf/builtin-ftrace.c | 43 ++++++++++++++++++++++++ > > 2 files changed, 47 insertions(+) > > > > diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt > > index 952e46669168..d79560dea19f 100644 > > --- a/tools/perf/Documentation/perf-ftrace.txt > > +++ b/tools/perf/Documentation/perf-ftrace.txt > > @@ -30,6 +30,10 @@ OPTIONS > > --verbose=:: > > Verbosity level. > > > > +-F:: > > +--funcs:: > > + List all available functions to trace. > > + > > -p:: > > --pid=:: > > Trace on existing process id (comma separated list). > > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c > > index 5f53da87040d..244cc8e6bd60 100644 > > --- a/tools/perf/builtin-ftrace.c > > +++ b/tools/perf/builtin-ftrace.c > > @@ -32,6 +32,7 @@ struct perf_ftrace { > > struct evlist *evlist; > > struct target target; > > const char *tracer; > > + bool list_avail_functions; > > struct list_head filters; > > struct list_head notrace; > > struct list_head graph_funcs; > > @@ -127,6 +128,43 @@ static int append_tracing_file(const char *name, const char *val) > > return __write_tracing_file(name, val, true); > > } > > > > +static int read_tracing_file_to_stdout(const char *name) > > +{ > > + char buf[4096]; > > + char *file; > > + int fd; > > + int ret = -1; > > + > > + file = get_tracing_file(name); > > + if (!file) { > > + pr_debug("cannot get tracing file: %s\n", name); > > + return -1; > > + } > > + > > + fd = open(file, O_RDONLY); > > + if (fd < 0) { > > + pr_debug("cannot open tracing file: %s: %s\n", > > + name, str_error_r(errno, buf, sizeof(buf))); > > + goto out; > > + } > > + > > + /* read contents to stdout */ > > + while (true) { > > + int n = read(fd, buf, sizeof(buf)); > > + if (n <= 0) > > + goto out_close; > > + if (fwrite(buf, n, 1, stdout) != 1) > > + goto out_close; > > + } > > + ret = 0; > > As I said before, there's no break in the loop above > so the ret can never be 0. > I see now. Just fixed it as: while (true) { int n = read(fd, buf, sizeof(buf)); - if (n <= 0) + if (n == 0) + break; + else if (n < 0) goto out_close; + Thanks! > Thanks > Namhyung > > > + > > +out_close: > > + close(fd); > > +out: > > + put_tracing_file(file); > > + return ret; > > +} > > + > > static int reset_tracing_cpu(void); > > static void reset_tracing_filters(void); > > > > @@ -301,6 +339,9 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv) > > signal(SIGCHLD, sig_handler); > > signal(SIGPIPE, sig_handler); > > > > + if (ftrace->list_avail_functions) > > + return read_tracing_file_to_stdout("available_filter_functions"); > > + > > if (reset_tracing_files(ftrace) < 0) { > > pr_err("failed to reset ftrace\n"); > > goto out; > > @@ -470,6 +511,8 @@ int cmd_ftrace(int argc, const char **argv) > > const struct option ftrace_options[] = { > > OPT_STRING('t', "tracer", &ftrace.tracer, "tracer", > > "tracer to use: function or function_graph (This option is deprecated)"), > > + OPT_BOOLEAN('F', "funcs", &ftrace.list_avail_functions, > > + "Show available functions to filter"), > > OPT_STRING('p', "pid", &ftrace.target.pid, "pid", > > "trace on existing process id"), > > OPT_INCR('v', "verbose", &verbose, > > -- > > 2.25.1 > > -- Cheers, Changbin Du