#ifndef _LINUX_FUTEX_H #define _LINUX_FUTEX_H #include <linux/sched.h> /* Second argument to futex syscall */ #define FUTEX_WAIT 0 #define FUTEX_WAKE 1 #define FUTEX_FD 2 #define FUTEX_REQUEUE 3 #define FUTEX_CMP_REQUEUE 4 #define FUTEX_WAKE_OP 5 /* * Support for robust futexes: the kernel cleans up held futexes at * thread exit time. */ /* * Per-lock list entry - embedded in user-space locks, somewhere close * to the futex field. (Note: user-space uses a double-linked list to * achieve O(1) list add and remove, but the kernel only needs to know * about the forward link) * * NOTE: this structure is part of the syscall ABI, and must not be * changed. */ struct robust_list { struct robust_list __user *next; }; /* * Per-thread list head: * * NOTE: this structure is part of the syscall ABI, and must only be * changed if the change is first communicated with the glibc folks. * (When an incompatible change is done, we'll increase the structure * size, which glibc will detect) */ struct robust_list_head { /* * The head of the list. Points back to itself if empty: */ struct robust_list list; /* * This relative offset is set by user-space, it gives the kernel * the relative position of the futex field to examine. This way * we keep userspace flexible, to freely shape its data-structure, * without hardcoding any particular offset into the kernel: */ long futex_offset; /* * The death of the thread may race with userspace setting * up a lock's links. So to handle this race, userspace first * sets this field to the address of the to-be-taken lock, * then does the lock acquire, and then adds itself to the * list, and then clears this field. Hence the kernel will * always have full knowledge of all locks that the thread * _might_ have taken. We check the owner TID in any case, * so only truly owned locks will be handled. */ struct robust_list __user *list_op_pending; }; /* * Are there any waiters for this robust futex: */ #define FUTEX_WAITERS 0x80000000 /* * The kernel signals via this bit that a thread holding a futex * has exited without unlocking the futex. The kernel also does * a FUTEX_WAKE on such futexes, after setting the bit, to wake * up any possible waiters: */ #define FUTEX_OWNER_DIED 0x40000000 /* * The rest of the robust-futex field is for the TID: */ #define FUTEX_TID_MASK 0x3fffffff /* * This limit protects against a deliberately circular list. * (Not worth introducing an rlimit for it) */ #define ROBUST_LIST_LIMIT 2048 long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout, unsigned long uaddr2, int val2, int val3); extern int handle_futex_death(u32 __user *uaddr, struct task_struct *curr); #ifdef CONFIG_FUTEX extern void exit_robust_list(struct task_struct *curr); #else static inline void exit_robust_list(struct task_struct *curr) { } #endif #define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */ #define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */ #define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */ #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */ #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */ #define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */ #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */ #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */ #define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */ #define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */ #define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */ #define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */ /* FUTEX_WAKE_OP will perform atomically int oldval = *(int *)UADDR2; *(int *)UADDR2 = oldval OP OPARG; if (oldval CMP CMPARG) wake UADDR2; */ #define FUTEX_OP(op, oparg, cmp, cmparg) \ (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \ | ((oparg & 0xfff) << 12) | (cmparg & 0xfff)) #endif