/* SPDX-License-Identifier: GPL-2.0 */#ifndef _VDSO_FUTEX_H#define _VDSO_FUTEX_H #include <uapi/linux/types.h> /** * __vdso_futex_robust_list64_try_unlock - Try to unlock an uncontended robust futex *					   with a 64-bit pending op pointer * @lock:	Pointer to the futex lock object * @tid:	The TID of the calling task * @pop:	Pointer to the task's robust_list_head::list_pending_op * * Return: The content of *@lock. On success this is the same as @tid. * * The function implements: *	if (atomic_try_cmpxchg(lock, &tid, 0)) *		*op = NULL; *	return tid; * * There is a race between a successful unlock and clearing the pending op * pointer in the robust list head. If the calling task is interrupted in the * race window and has to handle a (fatal) signal on return to user space then * the kernel handles the clearing of @pending_op before attempting to deliver * the signal. That ensures that a task cannot exit with a potentially invalid * pending op pointer. * * User space uses it in the following way: * * if (__vdso_futex_robust_list64_try_unlock(lock, tid, &pending_op) != tid) *	err = sys_futex($OP | FUTEX_ROBUST_UNLOCK,....); * * If the unlock attempt fails due to the FUTEX_WAITERS bit set in the lock, * then the syscall does the unlock, clears the pending op pointer and wakes the * requested number of waiters. */__u32 __vdso_futex_robust_list64_try_unlock(__u32 *lock, __u32 tid, __u64 *pop); /** * __vdso_futex_robust_list32_try_unlock - Try to unlock an uncontended robust futex *					   with a 32-bit pending op pointer * @lock:	Pointer to the futex lock object * @tid:	The TID of the calling task * @pop:	Pointer to the task's robust_list_head::list_pending_op * * Return: The content of *@lock. On success this is the same as @tid. * * Same as __vdso_futex_robust_list64_try_unlock() just with a 32-bit @pop pointer. */__u32 __vdso_futex_robust_list32_try_unlock(__u32 *lock, __u32 tid, __u32 *pop); #endif