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samples: make pidfd-metadata fail gracefully on older kernels

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Initialize pidfd to an invalid descriptor, to fail gracefully on
those kernels that do not implement CLONE_PIDFD and leave pidfd
unchanged.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Christian Brauner <christian@brauner.io>
This commit is contained in:
Дмитрий Левин 2019-06-23 14:28:00 +03:00 committed by Christian Brauner
parent 9014143bab
commit bee19cd8f2
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GPG Key ID: 8EB056D53EECB12D
1 changed files with 6 additions and 2 deletions
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8
samples/pidfd/pidfd-metadata.c
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@ -83,7 +83,7 @@ static int pidfd_metadata_fd(pid_t pid, int pidfd)
int main(int argc, char *argv[])
{
int pidfd = 0, ret = EXIT_FAILURE;
int pidfd = -1, ret = EXIT_FAILURE;
char buf[4096] = { 0 };
pid_t pid;
int procfd, statusfd;
@ -91,7 +91,11 @@ int main(int argc, char *argv[])
pid = pidfd_clone(CLONE_PIDFD, &pidfd);
if (pid < 0)
exit(ret);
err(ret, "CLONE_PIDFD");
if (pidfd == -1) {
warnx("CLONE_PIDFD is not supported by the kernel");
goto out;
}
procfd = pidfd_metadata_fd(pid, pidfd);
close(pidfd);