linux-kernel - [PATCH [RT] 11/14] optimize the !printk fastpath through the lock acquisition

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Date:	Thu, 21 Feb 2008 10:27:22 -0500
From:	Gregory Haskins <ghaskins@...ell.com>
To:	mingo@...e.hu, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	rostedt@...dmis.org, linux-rt-users@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, bill.huey@...il.com,
	kevin@...man.org, cminyard@...sta.com, dsingleton@...sta.com,
	dwalker@...sta.com, npiggin@...e.de, dsaxena@...xity.net,
	ak@...e.de, gregkh@...e.de, sdietrich@...ell.com,
	pmorreale@...ell.com, mkohari@...ell.com, ghaskins@...ell.com
Subject: [PATCH [RT] 11/14] optimize the !printk fastpath through the lock
	acquisition

Decorate the printk path with an "unlikely()"

Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
---

 kernel/rtmutex.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 122f143..ebdaa17 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -660,12 +660,12 @@ rt_spin_lock_fastlock(struct rt_mutex *lock,
 		void fastcall (*slowfn)(struct rt_mutex *lock))
 {
 	/* Temporary HACK! */
-	if (!current->in_printk)
-		might_sleep();
-	else if (in_atomic() || irqs_disabled())
+	if (unlikely(current->in_printk) && (in_atomic() || irqs_disabled()))
 		/* don't grab locks for printk in atomic */
 		return;
 
+	might_sleep();
+
 	if (likely(rt_mutex_cmpxchg(lock, NULL, current)))
 		rt_mutex_deadlock_account_lock(lock, current);
 	else
@@ -677,7 +677,7 @@ rt_spin_lock_fastunlock(struct rt_mutex *lock,
 			void fastcall (*slowfn)(struct rt_mutex *lock))
 {
 	/* Temporary HACK! */
-	if (current->in_printk && (in_atomic() || irqs_disabled()))
+	if (unlikely(current->in_printk) && (in_atomic() || irqs_disabled()))
 		/* don't grab locks for printk in atomic */
 		return;
 

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