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Date: Mon, 29 Dec 2008 15:49:53 -0800
From: "Darren Hart" <darren@...art.com>
To: "Ingo Molnar" <mingo@...e.hu>, linux-kernel@...r.kernel.org
Cc: "Peter Zijlstra" <peterz@...radead.org>,
"Thomas Gleixner" <tglx@...utronix.de>,
"Rusty Russell" <rusty@....ibm.com>,
"Darren Hart" <dvhltc@...ibm.com>
Subject: Re: [PATCH 1/2] futex: make futex_(get|put)_key() calls symmetric
On Mon, Dec 29, 2008 at 10:53 AM, Darren Hart <dvhltc@...ibm.com> wrote:
> Impact: cleanup
>
> This patch makes the calls to futex_get_key_refs() and futex_drop_key_refs()
> explicitly symmetric by only "putting" keys we successfully "got". Also
> cleanup a couple return points that didn't "put" after a successful "get".
>
> Build and boot tested on an x86_64 system.
Eeek. Apologies, I thought I had built/booted this one, but a test
for another patch later today shows I must not have as I am missing a
label and the build failed. Updated patch below, this one DOES build
and boot. Apologies!
futex: make futex_(get|put)_key() calls symmetric
From: Darren Hart <dvhltc@...ibm.com>
Impact: cleanup
This patch makes the calls to futex_get_key_refs() and futex_drop_key_refs()
explicitly symmetric by only "putting" keys we successfully "got". Also
cleanup a couple return points that didn't "put" after a successful "get".
Build and boot tested on an x86_64 system.
Signed-off-by: Darren Hart <dvhltc@...ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Rusty Russell <rusty@....ibm.com>
---
kernel/futex.c | 67 ++++++++++++++++++++++++++++++--------------------------
1 files changed, 36 insertions(+), 31 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index b4f87ba..c5ac55c 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -723,8 +723,8 @@ static int futex_wake(u32 __user *uaddr, int
fshared, int nr_wake, u32 bitset)
}
spin_unlock(&hb->lock);
-out:
put_futex_key(fshared, &key);
+out:
return ret;
}
@@ -748,7 +748,7 @@ retryfull:
goto out;
ret = get_futex_key(uaddr2, fshared, &key2);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
@@ -770,12 +770,12 @@ retry:
* but we might get them from range checking
*/
ret = op_ret;
- goto out;
+ goto out_put_keys;
#endif
if (unlikely(op_ret != -EFAULT)) {
ret = op_ret;
- goto out;
+ goto out_put_keys;
}
/*
@@ -789,7 +789,7 @@ retry:
ret = futex_handle_fault((unsigned long)uaddr2,
attempt);
if (ret)
- goto out;
+ goto out_put_keys;
goto retry;
}
@@ -827,10 +827,11 @@ retry:
spin_unlock(&hb1->lock);
if (hb1 != hb2)
spin_unlock(&hb2->lock);
-out:
+out_put_keys:
put_futex_key(fshared, &key2);
+out_put_key1:
put_futex_key(fshared, &key1);
-
+out:
return ret;
}
@@ -847,13 +848,13 @@ static int futex_requeue(u32 __user *uaddr1, int
fshared, u32 __user *uaddr2,
struct futex_q *this, *next;
int ret, drop_count = 0;
- retry:
+retry:
ret = get_futex_key(uaddr1, fshared, &key1);
if (unlikely(ret != 0))
goto out;
ret = get_futex_key(uaddr2, fshared, &key2);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
@@ -875,7 +876,7 @@ static int futex_requeue(u32 __user *uaddr1, int
fshared, u32 __user *uaddr2,
if (!ret)
goto retry;
- return ret;
+ goto out_put_keys;
}
if (curval != *cmpval) {
ret = -EAGAIN;
@@ -920,9 +921,11 @@ out_unlock:
while (--drop_count >= 0)
drop_futex_key_refs(&key1);
-out:
+out_put_keys:
put_futex_key(fshared, &key2);
+out_put_key1:
put_futex_key(fshared, &key1);
+out:
return ret;
}
@@ -983,7 +986,7 @@ static int unqueue_me(struct futex_q *q)
int ret = 0;
/* In the common case we don't take the spinlock, which is nice. */
- retry:
+retry:
lock_ptr = q->lock_ptr;
barrier();
if (lock_ptr != NULL) {
@@ -1165,11 +1168,11 @@ static int futex_wait(u32 __user *uaddr, int fshared,
q.pi_state = NULL;
q.bitset = bitset;
- retry:
+retry:
q.key = FUTEX_KEY_INIT;
ret = get_futex_key(uaddr, fshared, &q.key);
if (unlikely(ret != 0))
- goto out_release_sem;
+ goto out;
hb = queue_lock(&q);
@@ -1197,6 +1200,7 @@ static int futex_wait(u32 __user *uaddr, int fshared,
if (unlikely(ret)) {
queue_unlock(&q, hb);
+ put_futex_key(fshared, &q.key);
ret = get_user(uval, uaddr);
@@ -1206,7 +1210,7 @@ static int futex_wait(u32 __user *uaddr, int fshared,
}
ret = -EWOULDBLOCK;
if (uval != val)
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
/* Only actually queue if *uaddr contained val. */
queue_me(&q, hb);
@@ -1298,11 +1302,11 @@ static int futex_wait(u32 __user *uaddr, int fshared,
return -ERESTART_RESTARTBLOCK;
}
- out_unlock_release_sem:
+out_unlock_put_key:
queue_unlock(&q, hb);
-
- out_release_sem:
put_futex_key(fshared, &q.key);
+
+out:
return ret;
}
@@ -1351,16 +1355,16 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
}
q.pi_state = NULL;
- retry:
+retry:
q.key = FUTEX_KEY_INIT;
ret = get_futex_key(uaddr, fshared, &q.key);
if (unlikely(ret != 0))
- goto out_release_sem;
+ goto out;
- retry_unlocked:
+retry_unlocked:
hb = queue_lock(&q);
- retry_locked:
+retry_locked:
ret = lock_taken = 0;
/*
@@ -1381,14 +1385,14 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
*/
if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
ret = -EDEADLK;
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
}
/*
* Surprise - we got the lock. Just return to userspace:
*/
if (unlikely(!curval))
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
uval = curval;
@@ -1424,7 +1428,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
* We took the lock due to owner died take over.
*/
if (unlikely(lock_taken))
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
/*
* We dont have the lock. Look up the PI state (or create it if
@@ -1463,7 +1467,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
goto retry_locked;
}
default:
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
}
}
@@ -1554,16 +1558,17 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
destroy_hrtimer_on_stack(&to->timer);
return ret != -EINTR ? ret : -ERESTARTNOINTR;
- out_unlock_release_sem:
+out_unlock_put_key:
queue_unlock(&q, hb);
- out_release_sem:
+out_put_key:
put_futex_key(fshared, &q.key);
+out:
if (to)
destroy_hrtimer_on_stack(&to->timer);
return ret;
- uaddr_faulted:
+uaddr_faulted:
/*
* We have to r/w *(int __user *)uaddr, and we have to modify it
* atomically. Therefore, if we continue to fault after get_user()
@@ -1576,7 +1581,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
if (attempt++) {
ret = futex_handle_fault((unsigned long)uaddr, attempt);
if (ret)
- goto out_release_sem;
+ goto out_put_key;
goto retry_unlocked;
}
@@ -1668,9 +1673,9 @@ retry_unlocked:
out_unlock:
spin_unlock(&hb->lock);
-out:
put_futex_key(fshared, &key);
+out:
return ret;
pi_faulted:
--
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