linux-kernel - [PATCH 2/4] futex: add futex

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Date:	Thu,  8 Apr 2010 22:15:19 -0700
From:	dvhltc@...ibm.com
To:	linux-kernel@...r.kernel.org
Cc:	Darren Hart <dvhltc@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"Peter W. Morreale" <pmorreale@...ell.com>,
	Rik van Riel <riel@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Sven-Thorsten Dietrich <sdietrich@...ell.com>,
	Chris Mason <chris.mason@...cle.com>,
	John Cooper <john.cooper@...rd-harmonic.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Ulrich Drepper <drepper@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Avi Kivity <avi@...hat.com>
Subject: [PATCH 2/4] futex: add futex_q static initializer

From: Darren Hart <dvhltc@...ibm.com>

The futex_q struct has grown considerably over the last year or so. I
believe it now merits a static initializer to avoid uninitialized data
errors (having just spent more time than I care to admit debugging
an uninitialized q.bitset in an experimental new op code).

I originally planned on following the __THING_INITIALIZER/DECLARE_THING
method, but since we already had FUTEX_KEY_INIT, and I personally prefer
that method, I went that route.

Signed-off-by: Darren Hart <dvhltc@...ibm.com>
---
 kernel/futex.c |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index ed08cfd..2ae18cd 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -130,6 +130,12 @@ struct futex_q {
 	u32 bitset;
 };
 
+#define FUTEX_Q_INIT \
+	{ /* list gets initialized in queue_me()*/ \
+	  .task = NULL, NULL, FUTEX_KEY_INIT \
+	, NULL, NULL, NULL, FUTEX_BITSET_MATCH_ANY }
+
+
 /*
  * Hash buckets are shared by all the futex_keys that hash to the same
  * location.  Each key may have multiple futex_q structures, one for each task
@@ -1799,16 +1805,13 @@ static int futex_wait(u32 __user *uaddr, int flags, u32 val, ktime_t *abs_time,
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct restart_block *restart;
 	struct futex_hash_bucket *hb;
-	struct futex_q q;
+	struct futex_q q = FUTEX_Q_INIT;
 	int ret;
 
 	if (!bitset)
 		return -EINVAL;
 
-	q.pi_state = NULL;
 	q.bitset = bitset;
-	q.rt_waiter = NULL;
-	q.requeue_pi_key = NULL;
 
 	if (abs_time) {
 		to = &timeout;
@@ -1899,7 +1902,7 @@ static int futex_lock_pi(u32 __user *uaddr, int flags, int detect,
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct futex_hash_bucket *hb;
-	struct futex_q q;
+	struct futex_q q = FUTEX_Q_INIT;
 	int res, ret;
 
 	if (refill_pi_state_cache())
@@ -1913,9 +1916,6 @@ static int futex_lock_pi(u32 __user *uaddr, int flags, int detect,
 		hrtimer_set_expires(&to->timer, *time);
 	}
 
-	q.pi_state = NULL;
-	q.rt_waiter = NULL;
-	q.requeue_pi_key = NULL;
 retry:
 	q.key = FUTEX_KEY_INIT;
 	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
@@ -2206,7 +2206,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int flags,
 	struct rt_mutex *pi_mutex = NULL;
 	struct futex_hash_bucket *hb;
 	union futex_key key2;
-	struct futex_q q;
+	struct futex_q q = FUTEX_Q_INIT;
 	int res, ret;
 
 	if (!bitset)
@@ -2234,7 +2234,6 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int flags,
 	if (unlikely(ret != 0))
 		goto out;
 
-	q.pi_state = NULL;
 	q.bitset = bitset;
 	q.rt_waiter = &rt_waiter;
 	q.requeue_pi_key = &key2;
-- 
1.6.3.3

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