[patch 4/4] FUTEX: Tidy up the code

From: Thomas Gleixner
Date: Thu Jun 07 2007 - 20:31:15 EST

The recent PRIVATE and REQUEUE_PI changes to the futex code made it hard to read.
Tidy it up.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
kernel/futex.c | 192 ++++++++++++++++++++----------------------------
kernel/rtmutex-debug.c | 6 -
kernel/rtmutex.c | 6 -
kernel/rtmutex_common.h | 7 +
4 files changed, 88 insertions(+), 123 deletions(-)

Index: linux-2.6.22-rc4/kernel/rtmutex-debug.c
===================================================================
--- linux-2.6.22-rc4.orig/kernel/rtmutex-debug.c 2007-06-08 01:42:29.000000000 +0200
+++ linux-2.6.22-rc4/kernel/rtmutex-debug.c 2007-06-08 01:48:02.000000000 +0200
@@ -29,12 +29,6 @@

#include "rtmutex_common.h"

-#ifdef CONFIG_DEBUG_RT_MUTEXES
-# include "rtmutex-debug.h"
-#else
-# include "rtmutex.h"
-#endif
-
# define TRACE_WARN_ON(x) WARN_ON(x)
# define TRACE_BUG_ON(x) BUG_ON(x)

Index: linux-2.6.22-rc4/kernel/rtmutex.c
===================================================================
--- linux-2.6.22-rc4.orig/kernel/rtmutex.c 2007-06-08 01:44:54.000000000 +0200
+++ linux-2.6.22-rc4/kernel/rtmutex.c 2007-06-08 01:48:02.000000000 +0200
@@ -17,12 +17,6 @@

#include "rtmutex_common.h"

-#ifdef CONFIG_DEBUG_RT_MUTEXES
-# include "rtmutex-debug.h"
-#else
-# include "rtmutex.h"
-#endif
-
/*
* lock->owner state tracking:
*
Index: linux-2.6.22-rc4/kernel/rtmutex_common.h
===================================================================
--- linux-2.6.22-rc4.orig/kernel/rtmutex_common.h 2007-06-08 01:42:29.000000000 +0200
+++ linux-2.6.22-rc4/kernel/rtmutex_common.h 2007-06-08 01:48:02.000000000 +0200
@@ -154,4 +154,11 @@ extern int rt_mutex_adjust_prio_chain(st
struct task_struct *top_task);
extern void remove_waiter(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter);
+
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+# include "rtmutex-debug.h"
+#else
+# include "rtmutex.h"
+#endif
+
#endif
Index: linux-2.6.22-rc4/kernel/futex.c
===================================================================
--- linux-2.6.22-rc4.orig/kernel/futex.c 2007-06-08 01:46:59.000000000 +0200
+++ linux-2.6.22-rc4/kernel/futex.c 2007-06-08 01:48:02.000000000 +0200
@@ -56,12 +56,6 @@

#include "rtmutex_common.h"

-#ifdef CONFIG_DEBUG_RT_MUTEXES
-# include "rtmutex-debug.h"
-#else
-# include "rtmutex.h"
-#endif
-
#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)

/*
@@ -133,6 +127,24 @@ static struct futex_hash_bucket futex_qu
static struct vfsmount *futex_mnt;

/*
+ * Take mm->mmap_sem, when futex is shared
+ */
+static inline void futex_lock_mm(struct rw_semaphore *fshared)
+{
+ if (fshared)
+ down_read(fshared);
+}
+
+/*
+ * Release mm->mmap_sem, when the futex is shared
+ */
+static inline void futex_unlock_mm(struct rw_semaphore *fshared)
+{
+ if (fshared)
+ up_read(fshared);
+}
+
+/*
* We hash on the keys returned from get_futex_key (see below).
*/
static struct futex_hash_bucket *hash_futex(union futex_key *key)
@@ -302,7 +314,18 @@ void drop_futex_key_refs(union futex_key
}
EXPORT_SYMBOL_GPL(drop_futex_key_refs);

-static inline int get_futex_value_locked(u32 *dest, u32 __user *from)
+static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
+{
+ u32 curval;
+
+ pagefault_disable();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ pagefault_enable();
+
+ return curval;
+}
+
+static int get_futex_value_locked(u32 *dest, u32 __user *from)
{
int ret;

@@ -424,14 +447,12 @@ static struct task_struct * futex_find_g

rcu_read_lock();
p = find_task_by_pid(pid);
- if (!p)
- goto out_unlock;
- if ((current->euid != p->euid) && (current->euid != p->uid)) {
- p = NULL;
- goto out_unlock;
- }
- get_task_struct(p);
-out_unlock:
+
+ if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
+ p = ERR_PTR(-ESRCH);
+ else
+ get_task_struct(p);
+
rcu_read_unlock();

return p;
@@ -639,9 +660,7 @@ static int wake_futex_pi(u32 __user *uad
/* Keep the FUTEX_WAITER_REQUEUED flag if it was set */
newval |= (uval & FUTEX_WAITER_REQUEUED);

- pagefault_disable();
- curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
- pagefault_enable();
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

if (curval == -EFAULT)
ret = -EFAULT;
@@ -678,9 +697,7 @@ static int unlock_futex_pi(u32 __user *u
* There is no waiter, so we unlock the futex. The owner died
* bit has not to be preserved here. We are the owner:
*/
- pagefault_disable();
- oldval = futex_atomic_cmpxchg_inatomic(uaddr, uval, 0);
- pagefault_enable();
+ oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);

if (oldval == -EFAULT)
return oldval;
@@ -719,8 +736,7 @@ static int futex_wake(u32 __user *uaddr,
union futex_key key;
int ret;

- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr, fshared, &key);
if (unlikely(ret != 0))
@@ -744,8 +760,7 @@ static int futex_wake(u32 __user *uaddr,

spin_unlock(&hb->lock);
out:
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
return ret;
}

@@ -780,9 +795,7 @@ retry:
uval = curval;
newval = uval | FUTEX_WAITERS | FUTEX_WAITER_REQUEUED;

- pagefault_disable();
- curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
- pagefault_enable();
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

if (unlikely(curval == -EFAULT))
return -EFAULT;
@@ -830,11 +843,7 @@ static int futex_requeue_pi(u32 __user *
return -ENOMEM;

retry:
- /*
- * First take all the futex related locks:
- */
- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr1, fshared, &key1);
if (unlikely(ret != 0))
@@ -862,8 +871,7 @@ retry:
* If we would have faulted, release mmap_sem, fault
* it in and start all over again.
*/
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

ret = get_user(curval, uaddr1);

@@ -997,8 +1005,7 @@ out_unlock:
drop_futex_key_refs(&key1);

out:
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
return ret;
}

@@ -1018,8 +1025,7 @@ futex_wake_op(u32 __user *uaddr1, struct
int ret, op_ret, attempt = 0;

retryfull:
- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr1, fshared, &key1);
if (unlikely(ret != 0))
@@ -1065,7 +1071,7 @@ retry:
*/
if (attempt++) {
ret = futex_handle_fault((unsigned long)uaddr2,
- fshared, attempt);
+ fshared, attempt);
if (ret)
goto out;
goto retry;
@@ -1075,8 +1081,7 @@ retry:
* If we would have faulted, release mmap_sem,
* fault it in and start all over again.
*/
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

ret = get_user(dummy, uaddr2);
if (ret)
@@ -1113,8 +1118,7 @@ retry:
if (hb1 != hb2)
spin_unlock(&hb2->lock);
out:
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
return ret;
}

@@ -1133,8 +1137,7 @@ static int futex_requeue(u32 __user *uad
int ret, drop_count = 0;

retry:
- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr1, fshared, &key1);
if (unlikely(ret != 0))
@@ -1162,8 +1165,7 @@ static int futex_requeue(u32 __user *uad
* If we would have faulted, release mmap_sem, fault
* it in and start all over again.
*/
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

ret = get_user(curval, uaddr1);

@@ -1216,8 +1218,7 @@ out_unlock:
drop_futex_key_refs(&key1);

out:
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
return ret;
}

@@ -1386,10 +1387,7 @@ static int fixup_pi_state_owner(u32 __us
newval = (uval & FUTEX_OWNER_DIED) | newtid;
newval |= (uval & FUTEX_WAITER_REQUEUED);

- pagefault_disable();
- curval = futex_atomic_cmpxchg_inatomic(uaddr,
- uval, newval);
- pagefault_enable();
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

if (curval == -EFAULT)
ret = -EFAULT;
@@ -1407,6 +1405,7 @@ static int fixup_pi_state_owner(u32 __us
#define ARG3_SHARED 1

static long futex_wait_restart(struct restart_block *restart);
+
static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
u32 val, ktime_t *abs_time)
{
@@ -1421,8 +1420,7 @@ static int futex_wait(u32 __user *uaddr,

q.pi_state = NULL;
retry:
- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr, fshared, &q.key);
if (unlikely(ret != 0))
@@ -1459,8 +1457,7 @@ static int futex_wait(u32 __user *uaddr,
* If we would have faulted, release mmap_sem, fault it in and
* start all over again.
*/
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

ret = get_user(uval, uaddr);

@@ -1487,8 +1484,7 @@ static int futex_wait(u32 __user *uaddr,
* Now the futex is queued and we have checked the data, we
* don't want to hold mmap_sem while we sleep.
*/
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

/*
* There might have been scheduling since the queue_me(), as we
@@ -1548,9 +1544,9 @@ static int futex_wait(u32 __user *uaddr,
struct rt_mutex *lock = &q.pi_state->pi_mutex;

spin_lock(&lock->wait_lock);
- if (unlikely(q.waiter.task)) {
+ if (unlikely(q.waiter.task))
remove_waiter(lock, &q.waiter);
- }
+
spin_unlock(&lock->wait_lock);

if (rem)
@@ -1558,8 +1554,7 @@ static int futex_wait(u32 __user *uaddr,
else
ret = rt_mutex_timed_lock(lock, to, 1);

- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);
spin_lock(q.lock_ptr);

/*
@@ -1589,8 +1584,7 @@ static int futex_wait(u32 __user *uaddr,

/* Unqueue and drop the lock */
unqueue_me_pi(&q);
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

debug_rt_mutex_free_waiter(&q.waiter);

@@ -1628,8 +1622,7 @@ static int futex_wait(u32 __user *uaddr,
queue_unlock(&q, hb);

out_release_sem:
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
return ret;
}

@@ -1721,8 +1714,7 @@ static int futex_lock_pi(u32 __user *uad

q.pi_state = NULL;
retry:
- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr, fshared, &q.key);
if (unlikely(ret != 0))
@@ -1741,9 +1733,7 @@ static int futex_lock_pi(u32 __user *uad
*/
newval = current->pid;

- pagefault_disable();
- curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval);
- pagefault_enable();
+ curval = cmpxchg_futex_value_locked(uaddr, 0, newval);

if (unlikely(curval == -EFAULT))
goto uaddr_faulted;
@@ -1787,9 +1777,7 @@ static int futex_lock_pi(u32 __user *uad
lock_taken = 1;
}

- pagefault_disable();
- curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
- pagefault_enable();
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

if (unlikely(curval == -EFAULT))
goto uaddr_faulted;
@@ -1821,8 +1809,7 @@ static int futex_lock_pi(u32 __user *uad
* exit to complete.
*/
queue_unlock(&q, hb);
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
cond_resched();
goto retry;

@@ -1858,8 +1845,7 @@ static int futex_lock_pi(u32 __user *uad
* Now the futex is queued and we have checked the data, we
* don't want to hold mmap_sem while we sleep.
*/
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

WARN_ON(!q.pi_state);
/*
@@ -1873,8 +1859,7 @@ static int futex_lock_pi(u32 __user *uad
ret = ret ? 0 : -EWOULDBLOCK;
}

- if (fshared)
- down_read(fshared);
+ futex_lock_mm(fshared);
spin_lock(q.lock_ptr);

if (!ret) {
@@ -1911,8 +1896,7 @@ static int futex_lock_pi(u32 __user *uad

/* Unqueue and drop the lock */
unqueue_me_pi(&q);
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

return ret != -EINTR ? ret : -ERESTARTNOINTR;

@@ -1920,8 +1904,7 @@ static int futex_lock_pi(u32 __user *uad
queue_unlock(&q, hb);

out_release_sem:
- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);
return ret;

uaddr_faulted:
@@ -1943,8 +1926,7 @@ static int futex_lock_pi(u32 __user *uad
goto retry_unlocked;
}

- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

ret = get_user(uval, uaddr);
if (!ret && (uval != -EFAULT))
@@ -1975,11 +1957,8 @@ retry:
*/
if ((uval & FUTEX_TID_MASK) != current->pid)
return -EPERM;
- /*
- * First take all the futex related locks:
- */
- if (fshared)
- down_read(fshared);
+
+ futex_lock_mm(fshared);

ret = get_futex_key(uaddr, fshared, &key);
if (unlikely(ret != 0))
@@ -1994,11 +1973,8 @@ retry_unlocked:
* again. If it succeeds then we can return without waking
* anyone else up:
*/
- if (!(uval & FUTEX_OWNER_DIED)) {
- pagefault_disable();
- uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0);
- pagefault_enable();
- }
+ if (!(uval & FUTEX_OWNER_DIED))
+ uval = cmpxchg_futex_value_locked(uaddr, current->pid, 0);

if (unlikely(uval == -EFAULT))
goto pi_faulted;
@@ -2040,9 +2016,7 @@ retry_unlocked:
out_unlock:
spin_unlock(&hb->lock);
out:
- if (fshared)
- up_read(fshared);
-
+ futex_unlock_mm(fshared);
return ret;

pi_faulted:
@@ -2064,8 +2038,7 @@ pi_faulted:
goto retry_unlocked;
}

- if (fshared)
- up_read(fshared);
+ futex_unlock_mm(fshared);

ret = get_user(uval, uaddr);
if (!ret && (uval != -EFAULT))
@@ -2122,8 +2095,8 @@ static int futex_fd(u32 __user *uaddr, i

if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) {
printk(KERN_WARNING "Process `%s' used FUTEX_FD, which "
- "will be removed from the kernel in June 2007\n",
- current->comm);
+ "will be removed from the kernel in June 2007\n",
+ current->comm);
}

ret = -EINVAL;
@@ -2288,9 +2261,8 @@ retry:
* thread-death.) The rest of the cleanup is done in
* userspace.
*/
- mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
- /* Also keep the FUTEX_WAITER_REQUEUED flag if set */
- mval |= (uval & FUTEX_WAITER_REQUEUED);
+ mval = uval & (FUTEX_WAITERS | FUTEX_WAITER_REQUEUED);
+ mval |= FUTEX_OWNER_DIED;
nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);

if (nval == -EFAULT)
@@ -2303,10 +2275,8 @@ retry:
* Wake robust non-PI futexes here. The wakeup of
* PI futexes happens in exit_pi_state():
*/
- if (!pi) {
- if (uval & FUTEX_WAITERS)
+ if (!pi && (uval & FUTEX_WAITERS))
futex_wake(uaddr, &curr->mm->mmap_sem, 1);
- }
}
return 0;
}

--

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