Messages in this thread | | | Date | Fri, 12 Jan 2018 10:43:55 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH v2 2/3] trace-cmd: Remove the die() call from read_proc() |
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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);
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