On 21/05/2019 13.34, Christian Brauner wrote:
> 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)
> {
> DIR *dir;
> struct dirent *direntp;
>
> dir = opendir("/proc/self/fd");
> if (!dir)
> return -1;
>
> 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 == 0 || fd == 1 || fd == 2)
> continue;
> close(fd);
> }
>
> closedir(dir); /* cannot fail */
> return 0;
> }
Before anybody copy-pastes this, please note that it lacks a check for
fd == dirfd(dir). If all of /proc/self/fd is returned in the first
getdents() syscall one won't notice, but...
Rasmus
