3d4775df0a
The futex exit handling relies on PF_ flags. That's suboptimal as it requires a smp_mb() and an ugly lock/unlock of the exiting tasks pi_lock in the middle of do_exit() to enforce the observability of PF_EXITING in the futex code. Add a futex_state member to task_struct and convert the PF_EXITPIDONE logic over to the new state. The PF_EXITING dependency will be cleaned up in a later step. This prepares for handling various futex exit issues later. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20191106224556.149449274@linutronix.de
113 lines
3.2 KiB
C
113 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_FUTEX_H
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#define _LINUX_FUTEX_H
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#include <linux/sched.h>
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#include <linux/ktime.h>
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#include <uapi/linux/futex.h>
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struct inode;
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struct mm_struct;
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struct task_struct;
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/*
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* Futexes are matched on equal values of this key.
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* The key type depends on whether it's a shared or private mapping.
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* Don't rearrange members without looking at hash_futex().
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*
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* 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 :
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* 00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
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* (no reference on an inode or mm)
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* 01 : Shared futex (PTHREAD_PROCESS_SHARED)
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* mapped on a file (reference on the underlying inode)
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* 10 : Shared futex (PTHREAD_PROCESS_SHARED)
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* (but private mapping on an mm, and reference taken on it)
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*/
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#define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */
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#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
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union futex_key {
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struct {
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unsigned long pgoff;
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struct inode *inode;
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int offset;
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} shared;
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struct {
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unsigned long address;
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struct mm_struct *mm;
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int offset;
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} private;
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struct {
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unsigned long word;
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void *ptr;
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int offset;
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} both;
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};
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#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
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#ifdef CONFIG_FUTEX
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enum {
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FUTEX_STATE_OK,
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FUTEX_STATE_DEAD,
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};
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static inline void futex_init_task(struct task_struct *tsk)
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{
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tsk->robust_list = NULL;
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#ifdef CONFIG_COMPAT
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tsk->compat_robust_list = NULL;
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#endif
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INIT_LIST_HEAD(&tsk->pi_state_list);
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tsk->pi_state_cache = NULL;
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tsk->futex_state = FUTEX_STATE_OK;
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}
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/**
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* futex_exit_done - Sets the tasks futex state to FUTEX_STATE_DEAD
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* @tsk: task to set the state on
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*
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* Set the futex exit state of the task lockless. The futex waiter code
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* observes that state when a task is exiting and loops until the task has
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* actually finished the futex cleanup. The worst case for this is that the
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* waiter runs through the wait loop until the state becomes visible.
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*
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* This has two callers:
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*
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* - futex_mm_release() after the futex exit cleanup has been done
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*
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* - do_exit() from the recursive fault handling path.
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*
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* In case of a recursive fault this is best effort. Either the futex exit
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* code has run already or not. If the OWNER_DIED bit has been set on the
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* futex then the waiter can take it over. If not, the problem is pushed
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* back to user space. If the futex exit code did not run yet, then an
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* already queued waiter might block forever, but there is nothing which
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* can be done about that.
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*/
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static inline void futex_exit_done(struct task_struct *tsk)
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{
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tsk->futex_state = FUTEX_STATE_DEAD;
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}
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void futex_mm_release(struct task_struct *tsk);
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long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
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u32 __user *uaddr2, u32 val2, u32 val3);
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#else
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static inline void futex_init_task(struct task_struct *tsk) { }
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static inline void futex_mm_release(struct task_struct *tsk) { }
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static inline void futex_exit_done(struct task_struct *tsk) { }
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static inline long do_futex(u32 __user *uaddr, int op, u32 val,
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ktime_t *timeout, u32 __user *uaddr2,
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u32 val2, u32 val3)
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{
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return -EINVAL;
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}
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#endif
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#endif
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