Re: [patch] futex requeueing feature, futex-requeue-2.5.69-D4

Ingo Molnar (mingo@elte.hu)
Mon, 19 May 2003 12:30:11 +0200 (CEST)


On Mon, 19 May 2003, Andrew Morton wrote:

> page1 is leaked.

doh, indeed. -D4 patch attached. It also fixes the line-wrap noticed by
Christoph Hellwig. Patch applies, compiles and boots fine.

Ingo

--- linux/include/linux/futex.h.orig
+++ linux/include/linux/futex.h
@@ -5,7 +5,8 @@
#define FUTEX_WAIT (0)
#define FUTEX_WAKE (1)
#define FUTEX_FD (2)
+#define FUTEX_REQUEUE (3)

-extern asmlinkage long sys_futex(u32 __user *uaddr, int op, int val, struct timespec __user *utime);
+extern asmlinkage long sys_futex(u32 __user *uaddr, int op, int val, struct timespec __user *utime, u32 __user *uaddr2);

#endif
--- linux/kernel/fork.c.orig
+++ linux/kernel/fork.c
@@ -457,7 +457,7 @@ void mm_release(struct task_struct *tsk,
* not set up a proper pointer then tough luck.
*/
put_user(0, tidptr);
- sys_futex(tidptr, FUTEX_WAKE, 1, NULL);
+ sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL);
}
}

--- linux/kernel/compat.c.orig
+++ linux/kernel/compat.c
@@ -214,7 +214,7 @@ asmlinkage long compat_sys_sigprocmask(i
extern long do_futex(unsigned long, int, int, unsigned long);

asmlinkage long compat_sys_futex(u32 *uaddr, int op, int val,
- struct compat_timespec *utime)
+ struct compat_timespec *utime, u32 *uaddr2)
{
struct timespec t;
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
@@ -224,7 +224,7 @@ asmlinkage long compat_sys_futex(u32 *ua
return -EFAULT;
timeout = timespec_to_jiffies(&t) + 1;
}
- return do_futex((unsigned long)uaddr, op, val, timeout);
+ return do_futex((unsigned long)uaddr, op, val, timeout, (unsigned long)uaddr2);
}

asmlinkage long sys_setrlimit(unsigned int resource, struct rlimit *rlim);
--- linux/kernel/futex.c.orig
+++ linux/kernel/futex.c
@@ -2,6 +2,9 @@
* Fast Userspace Mutexes (which I call "Futexes!").
* (C) Rusty Russell, IBM 2002
*
+ * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
+ * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
+ *
* Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
* enough at me, Linus for the original (flawed) idea, Matthew
* Kirkwood for proof-of-concept implementation.
@@ -9,9 +12,6 @@
* "The futexes are also cursed."
* "But they come in a choice of three flavours!"
*
- * Generalized futexes for every mapping type, Ingo Molnar, 2002
- *
- *
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
@@ -216,6 +216,62 @@ static void futex_vcache_callback(vcache
spin_unlock(&futex_lock);
}

+/*
+ * Requeue all waiters hashed on one physical page to another
+ * physical page.
+ */
+static int futex_requeue(unsigned long uaddr1, int offset1, unsigned long uaddr2, int offset2, int num)
+{
+ struct list_head *i, *next, *head1, *head2;
+ struct page *page1 = NULL, *page2 = NULL;
+ int ret = 0;
+
+ lock_futex_mm();
+
+ page1 = __pin_page(uaddr1 - offset1);
+ if (!page1)
+ goto out;
+ page2 = __pin_page(uaddr2 - offset2);
+ if (!page2)
+ goto out;
+
+ head1 = hash_futex(page1, offset1);
+ head2 = hash_futex(page2, offset2);
+
+ list_for_each_safe(i, next, head1) {
+ struct futex_q *this = list_entry(i, struct futex_q, list);
+
+ if (this->page == page1 && this->offset == offset1) {
+ list_del_init(i);
+ __detach_vcache(&this->vcache);
+ if (++ret <= num) {
+ wake_up_all(&this->waiters);
+ if (this->filp)
+ send_sigio(&this->filp->f_owner,
+ this->fd, POLL_IN);
+ } else {
+ unpin_page(this->page);
+ __pin_page_atomic (page2);
+ list_add_tail(i, head2);
+ __attach_vcache(&this->vcache, uaddr2,
+ current->mm, futex_vcache_callback);
+ this->offset = offset2;
+ this->page = page2;
+ }
+ }
+ }
+
+out:
+ unlock_futex_mm();
+
+ if (page1)
+ unpin_page(page1);
+ if (page2)
+ unpin_page(page2);
+
+ return ret;
+}
+
static inline void __queue_me(struct futex_q *q, struct page *page,
unsigned long uaddr, int offset,
int fd, struct file *filp)
@@ -425,9 +481,9 @@ out:
return ret;
}

-long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout)
+long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout, unsigned long uaddr2)
{
- unsigned long pos_in_page;
+ unsigned long pos_in_page, pos_in_page2;
int ret;

pos_in_page = uaddr % PAGE_SIZE;
@@ -443,6 +499,14 @@ long do_futex(unsigned long uaddr, int o
case FUTEX_WAKE:
ret = futex_wake(uaddr, pos_in_page, val);
break;
+ case FUTEX_REQUEUE:
+ pos_in_page2 = uaddr2 % PAGE_SIZE;
+
+ /* Must be "naturally" aligned */
+ if (pos_in_page2 % sizeof(u32))
+ return -EINVAL;
+ ret = futex_requeue(uaddr, pos_in_page, uaddr2, pos_in_page2, val);
+ break;
case FUTEX_FD:
/* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
ret = futex_fd(uaddr, pos_in_page, val);
@@ -453,7 +517,7 @@ long do_futex(unsigned long uaddr, int o
return ret;
}

-asmlinkage long sys_futex(u32 __user *uaddr, int op, int val, struct timespec __user *utime)
+asmlinkage long sys_futex(u32 __user *uaddr, int op, int val, struct timespec __user *utime, u32 __user *uaddr2)
{
struct timespec t;
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
@@ -463,7 +527,7 @@ asmlinkage long sys_futex(u32 __user *ua
return -EFAULT;
timeout = timespec_to_jiffies(&t) + 1;
}
- return do_futex((unsigned long)uaddr, op, val, timeout);
+ return do_futex((unsigned long)uaddr, op, val, timeout, (unsigned long)uaddr2);
}

static struct super_block *

-
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