On Mon, Feb 19, 2018 at 10:21:34AM +0900, Namhyung Kim wrote: > Hello, > > On Wed, Feb 14, 2018 at 10:44:24AM +0800, changbin...@intel.com wrote: > > From: Changbin Du <changbin...@intel.com> > > > > Before this change, the '--graph-funcs', '--nograph-funcs' and > > '--trace-funcs' options didn't work as expected when the <func> doesn't > > exist. Because the kernel side hid possible errors. > > > > $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg > > 0) 0.140 us | rcu_all_qs(); > > 3) 0.304 us | mutex_unlock(); > > 0) 0.153 us | find_vma(); > > 3) 0.088 us | __fsnotify_parent(); > > 0) 6.145 us | handle_mm_fault(); > > 3) 0.089 us | fsnotify(); > > 3) 0.161 us | __sb_end_write(); > > 3) 0.710 us | SyS_close(); > > 3) 7.848 us | exit_to_usermode_loop(); > > > > On above example, I specified function filter 'abcdefg' but all functions > > are enabled. The expected error is hidden. > > > > The original fix is to make the kernel support '\0' as end of string: > > https://lkml.org/lkml/2018/1/16/116 > > > > But above fix cannot be compatible with old kernels. Then Namhyung Kim > > suggest adding a space after function name. > > > > This patch will append an '\n' when write tracing file. After this fix, > > the perf will report correct error state. Also let it print an error if > > reset_tracing_files() fails. > > > > Cc: Namhyung Kim <namhy...@kernel.org> > > Signed-off-by: Changbin Du <changbin...@intel.com> > > > > --- > > v3: Took Kim's suggestion that add a space after function name. > > v2: Rebase. > > --- > > tools/perf/builtin-ftrace.c | 15 +++++++++++++-- > > 1 file changed, 13 insertions(+), 2 deletions(-) > > > > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c > > index 25a42ac..9ffd748 100644 > > --- a/tools/perf/builtin-ftrace.c > > +++ b/tools/perf/builtin-ftrace.c > > @@ -72,6 +72,7 @@ static int __write_tracing_file(const char *name, const > > char *val, bool append) > > ssize_t size = strlen(val); > > int flags = O_WRONLY; > > char errbuf[512]; > > + char *val_copy; > > > > file = get_tracing_file(name); > > if (!file) { > > @@ -91,12 +92,20 @@ static int __write_tracing_file(const char *name, const > > char *val, bool append) > > goto out; > > } > > > > - if (write(fd, val, size) == size) > > + /* > > + * Copy the original value and append a '\n'. Without this, > > + * the kernel can hide possible errors. > > + */ > > + val_copy = strdup(val); > > Please check the return value. > Thanks, I will update. > Thanks, > Namhyung > > > > + val_copy[size] = '\n'; > > + > > + if (write(fd, val_copy, size + 1) == size + 1) > > ret = 0; > > else > > pr_debug("write '%s' to tracing/%s failed: %s\n", > > val, name, str_error_r(errno, errbuf, sizeof(errbuf))); > > > > + free(val_copy); > > close(fd); > > out: > > put_tracing_file(file); > > @@ -280,8 +289,10 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, > > int argc, const char **argv) > > signal(SIGCHLD, sig_handler); > > signal(SIGPIPE, sig_handler); > > > > - if (reset_tracing_files(ftrace) < 0) > > + if (reset_tracing_files(ftrace) < 0) { > > + pr_err("failed to reset ftrace\n"); > > goto out; > > + } > > > > /* reset ftrace buffer */ > > if (write_tracing_file("trace", "0") < 0) > > -- > > 2.7.4 > >
-- Thanks, Changbin Du
