On Thu, May 17, 2018 at 03:03:02PM +0200, Markus Armbruster wrote:
[...]
> > @@ -2502,7 +2525,9 @@ int monitor_fdset_get_fd(int64_t fdset_id, int flags)
> > MonFdset *mon_fdset;
> > MonFdsetFd *mon_fdset_fd;
> > int mon_fd_flags;
> > + int ret = -1;
>
> Suggest not to initialize ret, and instead ret = -1 on both failure
> paths.
[1]
But there is a third hidden failure path that we failed to find the fd
specified? In that case we still need that initial value.
But I didn't really notice that this function is returning error with
-1 paired with errno. So instead of set -1 here I may need to
initialize it to -ENOENT, and I can convert it back to errno when
return. Please see below.
>
> >
> > + qemu_mutex_lock(&mon_fdsets_lock);
> > QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
> > if (mon_fdset->id != fdset_id) {
> > continue;
> > @@ -2510,49 +2535,62 @@ int monitor_fdset_get_fd(int64_t fdset_id, int
> > flags)
> > QLIST_FOREACH(mon_fdset_fd, &mon_fdset->fds, next) {
> > mon_fd_flags = fcntl(mon_fdset_fd->fd, F_GETFL);
> > if (mon_fd_flags == -1) {
> > - return -1;
> > + goto out;
>
> Preexisting: we fail without setting errno. Smells buggy.
Indeed. Here I possibly need to set "ret = -errno" since at [2] below
the errno might be polluted by the mutex unlocking operation.
>
> Can we avoid setting errno and return a negative errno code instead?
Yes that'll be nice, but it's getting out of the scope of this
patchset. So I'll try to avoid touching that. I mean qemu_open() and
its callers.
>
> > }
> >
> > if ((flags & O_ACCMODE) == (mon_fd_flags & O_ACCMODE)) {
> > - return mon_fdset_fd->fd;
> > + ret = mon_fdset_fd->fd;
> > + goto out;
> > }
> > }
> > errno = EACCES;
> > - return -1;
> > + break;
> > }
> > -#endif
> > -
> > +out:
> > + qemu_mutex_unlock(&mon_fdsets_lock);
[2]
> > + return ret;
So in my next post I'll make sure I return -1 when error happens, and
errno should contain the correct (positive) error.
> > +#else
>
> #ifndef _WIN32 ... #endif becomes #ifndef _WIN32 ... #else ... #endif.
> I hate negative conditionals with else. Mind to swap?
Sure I can.
>
> > errno = ENOENT;
> > return -1;
> > +#endif
> > }
> >
> > int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
> > {
> > MonFdset *mon_fdset;
> > MonFdsetFd *mon_fdset_fd_dup;
> > + int ret = -1;
>
> Dead initializer, please remove.
IMHO it's the same as above [1], so we still need that, right?
>
> >
> > + qemu_mutex_lock(&mon_fdsets_lock);
> > QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
> > if (mon_fdset->id != fdset_id) {
> > continue;
> > }
> > QLIST_FOREACH(mon_fdset_fd_dup, &mon_fdset->dup_fds, next) {
> > if (mon_fdset_fd_dup->fd == dup_fd) {
> > - return -1;
> > + ret = -1;
> > + goto out;
> > }
> > }
> > mon_fdset_fd_dup = g_malloc0(sizeof(*mon_fdset_fd_dup));
> > mon_fdset_fd_dup->fd = dup_fd;
> > QLIST_INSERT_HEAD(&mon_fdset->dup_fds, mon_fdset_fd_dup, next);
> > - return 0;
> > + ret = 0;
> > + break;
> > }
> > - return -1;
> > +
> > +out:
> > + qemu_mutex_unlock(&mon_fdsets_lock);
> > + return ret;
> > }
> >
> > static int monitor_fdset_dup_fd_find_remove(int dup_fd, bool remove)
> > {
> > MonFdset *mon_fdset;
> > MonFdsetFd *mon_fdset_fd_dup;
> > + int ret = -1;
>
> Likewise.
Same as [1]?
Thanks,
--
Peter Xu
