e3f2ddeac7
Fix robust PI-futexes to be properly unlocked on unexpected exit. For this to work the kernel has to know whether a futex is a PI or a non-PI one, because the semantics are different. Since the space in relevant glibc data structures is extremely scarce, the best solution is to encode the 'PI' information in bit 0 of the robust list pointer. Existing (non-PI) glibc robust futexes have this bit always zero, so the ABI is kept. New glibc with PI-robust-futexes will set this bit. Further fixes from Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
140 lines
4.0 KiB
C
140 lines
4.0 KiB
C
#ifndef _LINUX_FUTEX_H
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#define _LINUX_FUTEX_H
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#include <linux/sched.h>
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/* Second argument to futex syscall */
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#define FUTEX_WAIT 0
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#define FUTEX_WAKE 1
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#define FUTEX_FD 2
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#define FUTEX_REQUEUE 3
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#define FUTEX_CMP_REQUEUE 4
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#define FUTEX_WAKE_OP 5
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#define FUTEX_LOCK_PI 6
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#define FUTEX_UNLOCK_PI 7
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#define FUTEX_TRYLOCK_PI 8
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/*
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* Support for robust futexes: the kernel cleans up held futexes at
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* thread exit time.
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*/
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/*
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* Per-lock list entry - embedded in user-space locks, somewhere close
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* to the futex field. (Note: user-space uses a double-linked list to
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* achieve O(1) list add and remove, but the kernel only needs to know
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* about the forward link)
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*
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* NOTE: this structure is part of the syscall ABI, and must not be
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* changed.
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*/
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struct robust_list {
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struct robust_list __user *next;
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};
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/*
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* Per-thread list head:
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*
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* NOTE: this structure is part of the syscall ABI, and must only be
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* changed if the change is first communicated with the glibc folks.
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* (When an incompatible change is done, we'll increase the structure
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* size, which glibc will detect)
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*/
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struct robust_list_head {
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/*
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* The head of the list. Points back to itself if empty:
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*/
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struct robust_list list;
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/*
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* This relative offset is set by user-space, it gives the kernel
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* the relative position of the futex field to examine. This way
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* we keep userspace flexible, to freely shape its data-structure,
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* without hardcoding any particular offset into the kernel:
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*/
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long futex_offset;
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/*
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* The death of the thread may race with userspace setting
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* up a lock's links. So to handle this race, userspace first
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* sets this field to the address of the to-be-taken lock,
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* then does the lock acquire, and then adds itself to the
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* list, and then clears this field. Hence the kernel will
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* always have full knowledge of all locks that the thread
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* _might_ have taken. We check the owner TID in any case,
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* so only truly owned locks will be handled.
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*/
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struct robust_list __user *list_op_pending;
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};
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/*
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* Are there any waiters for this robust futex:
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*/
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#define FUTEX_WAITERS 0x80000000
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/*
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* The kernel signals via this bit that a thread holding a futex
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* has exited without unlocking the futex. The kernel also does
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* a FUTEX_WAKE on such futexes, after setting the bit, to wake
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* up any possible waiters:
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*/
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#define FUTEX_OWNER_DIED 0x40000000
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/*
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* The rest of the robust-futex field is for the TID:
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*/
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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.
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* (Not worth introducing an rlimit for it)
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*/
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#define ROBUST_LIST_LIMIT 2048
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long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
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u32 __user *uaddr2, u32 val2, u32 val3);
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extern int
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handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
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#ifdef CONFIG_FUTEX
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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
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static inline void exit_robust_list(struct task_struct *curr)
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{
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}
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static inline void exit_pi_state_list(struct task_struct *curr)
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{
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}
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#endif
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#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
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#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
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#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
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#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
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#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
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#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
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#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
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#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
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#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
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#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
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#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
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#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
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/* FUTEX_WAKE_OP will perform atomically
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int oldval = *(int *)UADDR2;
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*(int *)UADDR2 = oldval OP OPARG;
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if (oldval CMP CMPARG)
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wake UADDR2; */
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#define FUTEX_OP(op, oparg, cmp, cmparg) \
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(((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
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| ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
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#endif
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