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Commit 9adef58b authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds
Browse files

futex: get_futex_key, get_key_refs and drop_key_refs 



lguest uses the convenient futex infrastructure for inter-domain I/O, so
expose get_futex_key, get_key_refs (renamed get_futex_key_refs) and
drop_key_refs (renamed drop_futex_key_refs).  Also means we need to expose the
union that these use.

No code changes.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent aa5bd7e9

include/linux/futex.h

+29 −0
Original line number Diff line number Diff line
@@ -100,6 +100,35 @@ long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout, 
extern int

handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);



/*

 * 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.

 * We set bit 0 to indicate if it's an inode-based key.

 */

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;

};

int get_futex_key(u32 __user *uaddr, union futex_key *key);

void get_futex_key_refs(union futex_key *key);

void drop_futex_key_refs(union futex_key *key);



#ifdef CONFIG_FUTEX

extern void exit_robust_list(struct task_struct *curr);

extern void exit_pi_state_list(struct task_struct *curr);

kernel/futex.c

+14 −36
Original line number Diff line number Diff line
@@ -48,38 +48,13 @@ 
#include <linux/pagemap.h>

#include <linux/syscalls.h>

#include <linux/signal.h>

#include <linux/module.h>

#include <asm/futex.h>



#include "rtmutex_common.h"



#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)



/*

 * 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.

 * We set bit 0 to indicate if it's an inode-based key.

 */

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;

};



/*

 * Priority Inheritance state:

 */
@@ -175,7 +150,7 @@ static inline int match_futex(union futex_key *key1, union futex_key *key2) 
 *

 * Should be called with &current->mm->mmap_sem but NOT any spinlocks.

 */

static int get_futex_key(u32 __user *uaddr, union futex_key *key)

int get_futex_key(u32 __user *uaddr, union futex_key *key)

{

	unsigned long address = (unsigned long)uaddr;

	struct mm_struct *mm = current->mm;
@@ -246,6 +221,7 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key) 
	}

	return err;

}

EXPORT_SYMBOL_GPL(get_futex_key);



/*

 * Take a reference to the resource addressed by a key.
@@ -254,7 +230,7 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key) 
 * NOTE: mmap_sem MUST be held between get_futex_key() and calling this

 * function, if it is called at all.  mmap_sem keeps key->shared.inode valid.

 */

static inline void get_key_refs(union futex_key *key)

inline void get_futex_key_refs(union futex_key *key)

{

	if (key->both.ptr != 0) {

		if (key->both.offset & 1)
@@ -263,12 +239,13 @@ static inline void get_key_refs(union futex_key *key) 
			atomic_inc(&key->private.mm->mm_count);

	}

}

EXPORT_SYMBOL_GPL(get_futex_key_refs);



/*

 * Drop a reference to the resource addressed by a key.

 * The hash bucket spinlock must not be held.

 */

static void drop_key_refs(union futex_key *key)

void drop_futex_key_refs(union futex_key *key)

{

	if (key->both.ptr != 0) {

		if (key->both.offset & 1)
@@ -277,6 +254,7 @@ static void drop_key_refs(union futex_key *key) 
			mmdrop(key->private.mm);

	}

}

EXPORT_SYMBOL_GPL(drop_futex_key_refs);



static inline int get_futex_value_locked(u32 *dest, u32 __user *from)

{
@@ -873,7 +851,7 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, 
				this->lock_ptr = &hb2->lock;

			}

			this->key = key2;

			get_key_refs(&key2);

			get_futex_key_refs(&key2);

			drop_count++;



			if (ret - nr_wake >= nr_requeue)
@@ -886,9 +864,9 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, 
	if (hb1 != hb2)

		spin_unlock(&hb2->lock);



	/* drop_key_refs() must be called outside the spinlocks. */

	/* drop_futex_key_refs() must be called outside the spinlocks. */

	while (--drop_count >= 0)

		drop_key_refs(&key1);

		drop_futex_key_refs(&key1);



out:

	up_read(&current->mm->mmap_sem);
@@ -906,7 +884,7 @@ queue_lock(struct futex_q *q, int fd, struct file *filp) 


	init_waitqueue_head(&q->waiters);



	get_key_refs(&q->key);

	get_futex_key_refs(&q->key);

	hb = hash_futex(&q->key);

	q->lock_ptr = &hb->lock;
@@ -925,7 +903,7 @@ static inline void 
queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)

{

	spin_unlock(&hb->lock);

	drop_key_refs(&q->key);

	drop_futex_key_refs(&q->key);

}



/*
@@ -980,7 +958,7 @@ static int unqueue_me(struct futex_q *q) 
		ret = 1;

	}



	drop_key_refs(&q->key);

	drop_futex_key_refs(&q->key);

	return ret;

}
@@ -999,7 +977,7 @@ static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb) 


	spin_unlock(&hb->lock);



	drop_key_refs(&q->key);

	drop_futex_key_refs(&q->key);

}



static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)