linux-kernel - [tip:core/futexes] futex: additional (get|put)_futex

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Date:	Thu, 12 Mar 2009 10:24:36 GMT
From:	Darren Hart <dvhltc@...ibm.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, dvhltc@...ibm.com, hpa@...or.com,
	mingo@...hat.com, rusty@...tcorp.com.au, peterz@...radead.org,
	tglx@...utronix.de, mingo@...e.hu
Subject: [tip:core/futexes] futex: additional (get|put)_futex_key() fixes

Commit-ID:  de87fcc124a5d4a171aa32707b3265608ebda6e7
Gitweb:     http://git.kernel.org/tip/de87fcc124a5d4a171aa32707b3265608ebda6e7
Author:     "Darren Hart" <dvhltc@...ibm.com>
AuthorDate: Thu, 12 Mar 2009 00:55:46 -0700
Commit:     Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 12 Mar 2009 11:20:56 +0100

futex: additional (get|put)_futex_key() fixes

Impact: fix races

futex_requeue and futex_lock_pi still had some bad
(get|put)_futex_key() usage. This patch adds the missing
put_futex_keys() and corrects a goto in futex_lock_pi() to avoid
a double get.

Build and boot tested on a 4 way Intel x86_64 workstation.
Passes basic pthread_mutex and PI tests out of
ltp/testcases/realtime.

Signed-off-by: Darren Hart <dvhltc@...ibm.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Cc: Rusty Russell <rusty@...tcorp.com.au>
LKML-Reference: <20090312075545.9856.75152.stgit@...n>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/futex.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index e6a4d72..4000454 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -802,8 +802,10 @@ retry:
 
 		ret = get_user(dummy, uaddr2);
 		if (ret)
-			return ret;
+			goto out_put_keys;
 
+		put_futex_key(fshared, &key2);
+		put_futex_key(fshared, &key1);
 		goto retryfull;
 	}
 
@@ -878,6 +880,9 @@ retry:
 			if (hb1 != hb2)
 				spin_unlock(&hb2->lock);
 
+			put_futex_key(fshared, &key2);
+			put_futex_key(fshared, &key1);
+
 			ret = get_user(curval, uaddr1);
 
 			if (!ret)
@@ -1453,6 +1458,7 @@ retry_locked:
 			 * exit to complete.
 			 */
 			queue_unlock(&q, hb);
+			put_futex_key(fshared, &q.key);
 			cond_resched();
 			goto retry;
 
@@ -1595,13 +1601,12 @@ uaddr_faulted:
 
 	ret = get_user(uval, uaddr);
 	if (!ret)
-		goto retry;
+		goto retry_unlocked;
 
-	if (to)
-		destroy_hrtimer_on_stack(&to->timer);
-	return ret;
+	goto out_put_key;
 }
 
+
 /*
  * Userspace attempted a TID -> 0 atomic transition, and failed.
  * This is the in-kernel slowpath: we look up the PI state (if any),
@@ -1705,6 +1710,7 @@ pi_faulted:
 	}
 
 	ret = get_user(uval, uaddr);
+	put_futex_key(fshared, &key);
 	if (!ret)
 		goto retry;
 
--
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