Message-ID: <CAP-5=fXJpD_f6dUqroVpqe-OX5kyOPc1zpbyOZoQtqvQWBGr=Q@mail.gmail.com>
Date: Wed, 30 Apr 2025 15:22:41 -0700
From: Ian Rogers <irogers@...gle.com>
To: Dirk Gouders <dirk@...ders.net>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
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Subject: Re: [PATCH v2 04/47] perf bench: Silence -Wshorten-64-to-32 warnings

On Wed, Apr 30, 2025 at 3:19 PM Dirk Gouders <dirk@...ders.net> wrote:
>
> Ian Rogers <irogers@...gle.com> writes:
>
> > On Wed, Apr 30, 2025 at 1:23 PM Dirk Gouders <dirk@...ders.net> wrote:
> >>
> >> Hi Ian,
> >>
> >> considering so many eyes looking at this, I am probably wrong.
> >>
> >> So, this is only a "gauge reply" to see if it's worth I really read
> >> through all the commits ;-)
> >>
> >> Ian Rogers <irogers@...gle.com> writes:
> >>
> >> [SNIP]
> >>
> >> > diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c
> >> > index 70139036d68f..b847213fd616 100644
> >> > --- a/tools/perf/bench/sched-pipe.c
> >> > +++ b/tools/perf/bench/sched-pipe.c
> >> > @@ -102,7 +102,8 @@ static const char * const bench_sched_pipe_usage[] = {
> >> >  static int enter_cgroup(int nr)
> >> >  {
> >> >       char buf[32];
> >> > -     int fd, len, ret;
> >> > +     int fd;
> >> > +     ssize_t ret, len;
> >> >       int saved_errno;
> >> >       struct cgroup *cgrp;
> >> >       pid_t pid;
> >> > @@ -118,7 +119,7 @@ static int enter_cgroup(int nr)
> >> >       cgrp = cgrps[nr];
> >> >
> >> >       if (threaded)
> >> > -             pid = syscall(__NR_gettid);
> >> > +             pid = (pid_t)syscall(__NR_gettid);
> >> >       else
> >> >               pid = getpid();
> >> >
> >> > @@ -172,23 +173,25 @@ static void exit_cgroup(int nr)
> >> >
> >> >  static inline int read_pipe(struct thread_data *td)
> >> >  {
> >> > -     int ret, m;
> >> > +     ssize_t ret;
> >> > +     int m;
> >> >  retry:
> >> >       if (nonblocking) {
> >> >               ret = epoll_wait(td->epoll_fd, &td->epoll_ev, 1, -1);
> >>
> >> The epoll_wait(), I know of, returns an int and not ssize_t.
> >>
> >> That shouldn't show up, because it doesn't cause real problems...
> >
> > So the function is read_pipe so it should probably return a ssize_t. I
> > stopped short of that but made ret a ssize_t to silence the truncation
> > warning on the read call. Assigning smaller to bigger is of course not
> > an issue for epoll_wait.
>
> Oh yes, I missed that ret is also used for the result of read().
>
> Some lines down there is also a combination of
>
> ret = enter_cgroup() (which is int)
>
> and
>
> ret = write()
>
>
> Just confusing but yes, because ret is also used for read() and write()
> in those cases it should be ssize_t.
>
> I'm sorry for the noise.

No worries, I'm appreciative of the eyes. I suspect we'll only pick up
the first patches in this series to fix what is a bug on ARM. I think
I'm responsible for too much noise here ;-)

Thanks,
Ian

> Best regards,
>
> Dirk

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