On Thu, Jan 30, 2025 at 08:40:26PM +0000, Lorenzo Stoakes wrote: > It is useful to be able to utilise the pidfd mechanism to reference the > current thread or process (from a userland point of view - thread group > leader from the kernel's point of view). > > Therefore introduce PIDFD_SELF_THREAD to refer to the current thread, and > PIDFD_SELF_THREAD_GROUP to refer to the current thread group leader. > > For convenience and to avoid confusion from userland's perspective we alias > these: > > * PIDFD_SELF is an alias for PIDFD_SELF_THREAD - This is nearly always what > the user will want to use, as they would find it surprising if for > instance fd's were unshared()'d and they wanted to invoke pidfd_getfd() > and that failed. > > * PIDFD_SELF_PROCESS is an alias for PIDFD_SELF_THREAD_GROUP - Most users > have no concept of thread groups or what a thread group leader is, and > from userland's perspective and nomenclature this is what userland > considers to be a process. > > We adjust pidfd_get_task() and the pidfd_send_signal() system call with > specific handling for this, implementing this functionality for > process_madvise(), process_mrelease() (albeit, using it here wouldn't > really make sense) and pidfd_send_signal(). > > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
