On Wed, Jun 03, 2020 at 01:30:57AM +0200, Florian Weimer wrote:
> * Christian Brauner:
>
> > The performance is striking. For good measure, comparing the following
> > simple close_all_fds() userspace implementation that is essentially just
> > glibc's version in [6]:
> >
> > static int close_all_fds(void)
> > {
> > int dir_fd;
> > DIR *dir;
> > struct dirent *direntp;
> >
> > dir = opendir("/proc/self/fd");
> > if (!dir)
> > return -1;
> > dir_fd = dirfd(dir);
> > while ((direntp = readdir(dir))) {
> > int fd;
> > if (strcmp(direntp->d_name, ".") == 0)
> > continue;
> > if (strcmp(direntp->d_name, "..") == 0)
> > continue;
> > fd = atoi(direntp->d_name);
> > if (fd == dir_fd || fd == 0 || fd == 1 || fd == 2)
> > continue;
> > close(fd);
> > }
> > closedir(dir);
> > return 0;
> > }
> >
>
> > [6]: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/grantpt.c;h=2030e07fa6e652aac32c775b8c6e005844c3c4eb;hb=HEAD#l17
> > Note that this is an internal implementation that is not exported.
> > Currently, libc seems to not provide an exported version of this
> > because of missing kernel support to do this.
>
> Just to be clear, this code is not compiled into glibc anymore in
> typical configurations. I have posted a patch to turn grantpt into a
> no-op: <https://sourceware.org/pipermail/libc-alpha/2020-May/114379.html>
That's great! (I remember commenting on that thread.)
