On Thu, 21 Dec 2017 17:25:19 +0200
"Vladislav Valtchev (VMware)" <vladislav.valtc...@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.valtc...@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);
