NAME¶

PR_SET_CHILD_SUBREAPER - set/unset the "child subreaper" attribute of the calling process

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <linux/prctl.h>  /* Definition of PR_* constants */
#include <sys/prctl.h>

int prctl(PR_SET_CHILD_SUBREAPER, long set);

DESCRIPTION¶

If set is nonzero, set the "child subreaper" attribute of the calling process; if set is zero, unset the attribute.

A subreaper fulfills the role of init(1) for its descendant processes. When a process becomes orphaned (i.e., its immediate parent terminates), then that process will be reparented to the nearest still living ancestor subreaper. Subsequently, calls to getppid(2) in the orphaned process will now return the PID of the subreaper process, and when the orphan terminates, it is the subreaper process that will receive a SIGCHLD signal and will be able to wait(2) on the process to discover its termination status.

The setting of the "child subreaper" attribute is not inherited by children created by fork(2) and clone(2). The setting is preserved across execve(2).

Establishing a subreaper process is useful in session management frameworks where a hierarchical group of processes is managed by a subreaper process that needs to be informed when one of the processes—for example, a double-forked daemon—terminates (perhaps so that it can restart that process). Some init(1) frameworks (e.g., systemd(1)) employ a subreaper process for similar reasons.

RETURN VALUE¶

On success, 0 is returned. On error, -1 is returned, and errno is set to indicate the error.

STANDARDS¶

Linux.

HISTORY¶

Linux 3.4.

SEE ALSO¶

prctl(2), PR_GET_CHILD_SUBREAPER(2const)