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include/linux/futex.h
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#ifndef _LINUX_FUTEX_H #define _LINUX_FUTEX_H |
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#include <linux/sched.h> |
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union ktime; |
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/* Second argument to futex syscall */ |
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#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 |
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#define FUTEX_LOCK_PI 6 #define FUTEX_UNLOCK_PI 7 #define FUTEX_TRYLOCK_PI 8 |
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#define FUTEX_PRIVATE_FLAG 128 #define FUTEX_CMD_MASK ~FUTEX_PRIVATE_FLAG #define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG) #define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG) #define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG) #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG) #define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG) #define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG) #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG) #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG) |
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/* * 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 /* |
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* The rest of the robust-futex field is for the TID: */ |
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#define FUTEX_TID_MASK 0x3fffffff |
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/* |
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* This limit protects against a deliberately circular list. * (Not worth introducing an rlimit for it) |
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*/ |
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#define ROBUST_LIST_LIMIT 2048 |
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#ifdef __KERNEL__ |
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long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout, |
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u32 __user *uaddr2, u32 val2, u32 val3); |
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extern int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi); |
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/* * Futexes are matched on equal values of this key. * The key type depends on whether it's a shared or private mapping. * Don't rearrange members without looking at hash_futex(). * * offset is aligned to a multiple of sizeof(u32) (== 4) by definition. |
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* We use the two low order bits of offset to tell what is the kind of key : * 00 : Private process futex (PTHREAD_PROCESS_PRIVATE) * (no reference on an inode or mm) * 01 : Shared futex (PTHREAD_PROCESS_SHARED) * mapped on a file (reference on the underlying inode) * 10 : Shared futex (PTHREAD_PROCESS_SHARED) * (but private mapping on an mm, and reference taken on it) */ #define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */ #define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */ |
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union futex_key { struct { unsigned long pgoff; struct inode *inode; int offset; } shared; struct { unsigned long address; struct mm_struct *mm; int offset; } private; struct { unsigned long word; void *ptr; int offset; } both; }; |
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int get_futex_key(u32 __user *uaddr, struct rw_semaphore *shared, union futex_key *key); |
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void get_futex_key_refs(union futex_key *key); void drop_futex_key_refs(union futex_key *key); |
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#ifdef CONFIG_FUTEX extern void exit_robust_list(struct task_struct *curr); |
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extern void exit_pi_state_list(struct task_struct *curr); |
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#else static inline void exit_robust_list(struct task_struct *curr) { } |
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static inline void exit_pi_state_list(struct task_struct *curr) { } |
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#endif |
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#endif /* __KERNEL__ */ |
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#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)) |
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#endif |