| Message ID | 20171221152520.25867-3-vladislav.valtchev@gmail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | trace-cmd: Integrate stack tracer status in 'stat' | expand |
On Thu, 21 Dec 2017 17:25:19 +0200 "Vladislav Valtchev (VMware)" <vladislav.valtchev@gmail.com> wrote: > As trace-stack.c's read_proc() function is going to be used by trace-cmd stat, > we don't want it to make the program die in case something went wrong. > Therefore, this simple patch makes read_proc() to just return -1 in case the > proc file was empty or read() failed with an error, instead of using die(). > > Signed-off-by: Vladislav Valtchev (VMware) <vladislav.valtchev@gmail.com> > --- > trace-stack.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/trace-stack.c b/trace-stack.c > index c1058ca..d55d994 100644 > --- a/trace-stack.c > +++ b/trace-stack.c > @@ -79,9 +79,9 @@ static int read_proc(int *status) > > n = read(fd, buf, sizeof(buf)); > > - /* We assume that the file is never empty we got no errors. */ > + /* The file was empty or read() failed with an error. */ > if (n <= 0) > - die("error reading %s", PROC_FILE); > + return -1; > > /* Does this file have more than 63 characters?? */ > if (n >= sizeof(buf)) But you need to handle the error cases for the users of read_proc(). >From the previous patch: static void change_stack_tracer_status(int new_status) { char buf[1]; int status; int fd; int n; if (read_proc(&status) > 0 && status == new_status) return; /* nothing to do */ We should not continue if read_proc() fails. Should move the die here: ret = read_proc(&status); if (ret < 0) die("error reading %s", PROC_FILE); if (ret > 0 && status == new_status) return; /* nothing to do */ -- Steve fd = open(PROC_FILE, O_WRONLY); if (fd < 0) die("writing %s", PROC_FILE); buf[0] = new_status + '0'; n = write(fd, buf, 1);
On Fri, 2018-01-12 at 10:43 -0500, Steven Rostedt wrote: > > But you need to handle the error cases for the users of read_proc(). > From the previous patch: > > static void change_stack_tracer_status(int new_status) > { > char buf[1]; > int status; > int fd; > int n; > > if (read_proc(&status) > 0 && status == new_status) > return; /* nothing to do */ > > We should not continue if read_proc() fails. Should move the die here: > > ret = read_proc(&status); > if (ret < 0) > die("error reading %s", PROC_FILE); > > if (ret > 0 && status == new_status) > return; /* nothing to do */ > > -- Steve > You're totally right. I overlooked at this detail.
diff --git a/trace-stack.c b/trace-stack.c index c1058ca..d55d994 100644 --- a/trace-stack.c +++ b/trace-stack.c @@ -79,9 +79,9 @@ static int read_proc(int *status) n = read(fd, buf, sizeof(buf)); - /* We assume that the file is never empty we got no errors. */ + /* The file was empty or read() failed with an error. */ if (n <= 0) - die("error reading %s", PROC_FILE); + return -1; /* Does this file have more than 63 characters?? */ if (n >= sizeof(buf))
As trace-stack.c's read_proc() function is going to be used by trace-cmd stat, we don't want it to make the program die in case something went wrong. Therefore, this simple patch makes read_proc() to just return -1 in case the proc file was empty or read() failed with an error, instead of using die(). Signed-off-by: Vladislav Valtchev (VMware) <vladislav.valtchev@gmail.com> --- trace-stack.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)