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Date: Mon, 5 Apr 2010 13:23:56 -0700
From: Darren Hart <dvhltc@...ibm.com>
To: linux-kernel@...r.kernel.org
Cc: 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>,
Avi Kivity <avi@...hat.com>, Darren Hart <dvhltc@...ibm.com>
Subject: [PATCH 3/6] futex: refactor futex_lock_pi_atomic
Prepare for FUTEX_LOCK by refactoring futex_lock_pi_atomic() into
lock_futex_atomic() and lock_pi_futex_atomic(). The name change is meant to
reflect the naming convention in futex.c that futex_*() functions map directly
to futex op codes and the others are internal helper functions.
Signed-off-by: Darren Hart <dvhltc@...ibm.com>
===================================================================
---
kernel/futex.c | 79 +++++++++++++++++++++++++++++++++++++------------------
1 files changed, 53 insertions(+), 26 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 2ae18cd..8c1bb16 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -625,30 +625,23 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
}
/**
- * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
- * @uaddr: the pi futex user address
- * @hb: the pi futex hash bucket
- * @key: the futex key associated with uaddr and hb
- * @ps: the pi_state pointer where we store the result of the
- * lookup
- * @task: the task to perform the atomic lock work for. This will
- * be "current" except in the case of requeue pi.
- * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
+ * lock_futex_atomic() - Try to acquire the futex lock atomically
+ * @uaddr: user address of the futex
+ * @task: the task to perform the atomic lock work for.
+ * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
+ *
+ * The hb->lock shall be held by the caller.
*
* Returns:
* 0 - ready to wait
* 1 - acquired the lock
* <0 - error
- *
- * The hb->lock and futex_key refs shall be held by the caller.
*/
-static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
- union futex_key *key,
- struct futex_pi_state **ps,
- struct task_struct *task, int set_waiters)
+static int lock_futex_atomic(u32 __user *uaddr, struct task_struct *task,
+ int set_waiters)
{
- int lock_taken, ret, ownerdied = 0;
u32 uval, newval, curval;
+ int lock_taken, ret;
retry:
ret = lock_taken = 0;
@@ -695,10 +688,10 @@ retry:
*
* This is safe as we are protected by the hash bucket lock !
*/
- if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
+ if (unlikely((curval & FUTEX_OWNER_DIED) ||
+ !(curval & FUTEX_TID_MASK))) {
/* Keep the OWNER_DIED bit */
newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(task);
- ownerdied = 0;
lock_taken = 1;
}
@@ -715,10 +708,46 @@ retry:
if (unlikely(lock_taken))
return 1;
+ return ret;
+}
+
+/**
+ * lock_pi_futex_atomic() - Atomic work required to acquire a pi aware futex
+ * @uaddr: the pi futex user address
+ * @hb: the pi futex hash bucket
+ * @key: the futex key associated with uaddr and hb
+ * @ps: the pi_state pointer where we store the result of the
+ * lookup
+ * @task: the task to perform the atomic lock work for. This will
+ * be "current" except in the case of requeue pi.
+ * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
+ *
+ * Returns:
+ * 0 - ready to wait
+ * 1 - acquired the lock
+ * <0 - error
+ *
+ * The hb->lock and futex_key refs shall be held by the caller.
+ */
+static int lock_pi_futex_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
+ union futex_key *key,
+ struct futex_pi_state **ps,
+ struct task_struct *task, int set_waiters)
+{
+ u32 uval;
+ int ret;
+
+retry:
+ ret = lock_futex_atomic(uaddr, task, set_waiters);
+ if (ret)
+ return ret;
+
/*
* We dont have the lock. Look up the PI state (or create it if
* we are the first waiter):
*/
+ if (get_futex_value_locked(&uval, uaddr))
+ return -EFAULT;
ret = lookup_pi_state(uval, hb, key, ps);
if (unlikely(ret)) {
@@ -729,7 +758,7 @@ retry:
* OWNER_DIED bit is set to figure out whether
* this is a robust futex or not.
*/
- if (get_futex_value_locked(&curval, uaddr))
+ if (get_futex_value_locked(&uval, uaddr))
return -EFAULT;
/*
@@ -737,10 +766,8 @@ retry:
* futex. The code above will take the futex
* and return happy.
*/
- if (curval & FUTEX_OWNER_DIED) {
- ownerdied = 1;
+ if (uval & FUTEX_OWNER_DIED)
goto retry;
- }
default:
break;
}
@@ -1100,7 +1127,7 @@ void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
*
* Try and get the lock on behalf of the top waiter if we can do it atomically.
* Wake the top waiter if we succeed. If the caller specified set_waiters,
- * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
+ * then direct lock_pi_futex_atomic() to force setting the FUTEX_WAITERS bit.
* hb1 and hb2 must be held by the caller.
*
* Returns:
@@ -1124,7 +1151,7 @@ static int futex_proxy_trylock_atomic(u32 __user *pifutex,
/*
* Find the top_waiter and determine if there are additional waiters.
* If the caller intends to requeue more than 1 waiter to pifutex,
- * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
+ * force lock_pi_futex_atomic() to set the FUTEX_WAITERS bit now,
* as we have means to handle the possible fault. If not, don't set
* the bit unecessarily as it will force the subsequent unlock to enter
* the kernel.
@@ -1144,7 +1171,7 @@ static int futex_proxy_trylock_atomic(u32 __user *pifutex,
* the contended case or if set_waiters is 1. The pi_state is returned
* in ps in contended cases.
*/
- ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
+ ret = lock_pi_futex_atomic(pifutex, hb2, key2, ps, top_waiter->task,
set_waiters);
if (ret == 1)
requeue_pi_wake_futex(top_waiter, key2, hb2);
@@ -1925,7 +1952,7 @@ retry:
retry_private:
hb = queue_lock(&q);
- ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0);
+ ret = lock_pi_futex_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0);
if (unlikely(ret)) {
switch (ret) {
case 1:
--
1.6.3.3
--
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