linux-kernel - [PATCH 5/6] futex: handle timeout inside adaptive lock spin

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Date:	Mon,  5 Apr 2010 13:23:58 -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 5/6] futex: handle timeout inside adaptive lock spin

Signed-off-by: Darren Hart <dvhltc@...ibm.com>
---
 kernel/futex.c |   24 +++++++++++++++++++++---
 1 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index c33ac2a..af61dcd 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2385,6 +2385,7 @@ out:
 /**
  * trylock_futex_adaptive() - Try to acquire the futex lock in a busy loop
  * @uaddr: the futex user address
+ * @timeout: absolute timeout or NULL if none
  *
  * Try to acquire a futex lock in a loop until the owner changes or the owner
  * is descheduled. To lock the futex, set the value to the current TID.
@@ -2394,10 +2395,11 @@ out:
  *  1 - Futex lock acquired
  * <0 - On error
  */
-static int trylock_futex_adaptive(u32 __user *uaddr)
+static int trylock_futex_adaptive(u32 __user *uaddr, ktime_t *timeout)
 {
 	int ret = 0;
 	u32 curval;
+	ktime_t now;
 
 	for (;;) {
 		struct thread_info *owner;
@@ -2433,6 +2435,22 @@ static int trylock_futex_adaptive(u32 __user *uaddr)
 		if (need_resched())
 			break;
 
+		if (timeout) {
+			now = ktime_get();
+/* FIXME: consider creating ktime_less_than(lhs, rhs) */
+#if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
+			if (timeout->tv64 < now.tv64)
+				break;
+#else
+			if (timeout->sec < now.sec ||
+			    (timeout->sec == now.sec &&
+			     timeout->nsec < now.nsec)) {
+				ret = -ETIMEDOUT;
+				break;
+			}
+#endif
+		}
+
 		cpu_relax();
 	}
 	return ret;
@@ -2480,7 +2498,7 @@ retry:
 #ifdef CONFIG_SMP
 	if (flags & FLAGS_ADAPTIVE) {
 		preempt_disable();
-		ret = trylock_futex_adaptive(uaddr);
+		ret = trylock_futex_adaptive(uaddr, time);
 		preempt_enable();
 
 		/* We got the lock. */
@@ -2489,7 +2507,7 @@ retry:
 			goto out;
 		}
 
-		/* We encountered an error, -EFAULT most likely. */
+		/* We encountered an error, -EFAULT or -ETIMEDOUT */
 		if (ret)
 			goto out;
 	}
-- 
1.6.3.3

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