From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932325Ab2BATtq (ORCPT ); Wed, 1 Feb 2012 14:49:46 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:41224 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932270Ab2BATto (ORCPT ); Wed, 1 Feb 2012 14:49:44 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, "Paul E. McKenney" , "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 22/41] rcu: Simplify unboosting checks Date: Wed, 1 Feb 2012 11:41:40 -0800 Message-Id: <1328125319-5205-22-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120201194131.GA10028@linux.vnet.ibm.com> <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12020119-3534-0000-0000-0000051AC76C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" This is a port of commit #82e78d80 from TREE_PREEMPT_RCU to TINY_PREEMPT_RCU. This commit uses the fact that current->rcu_boost_mutex is set any time that the RCU_READ_UNLOCK_BOOSTED flag is set in the current->rcu_read_unlock_special bitmask. This allows tests of the bit to be changed to tests of the pointer, which in turn allows the RCU_READ_UNLOCK_BOOSTED flag to be eliminated. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- include/linux/sched.h | 3 +-- kernel/rcutiny_plugin.h | 10 ++++++---- 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 4032ec1..1db119f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1864,8 +1864,7 @@ extern void task_clear_jobctl_pending(struct task_struct *task, #ifdef CONFIG_PREEMPT_RCU #define RCU_READ_UNLOCK_BLOCKED (1 << 0) /* blocked while in RCU read-side. */ -#define RCU_READ_UNLOCK_BOOSTED (1 << 1) /* boosted while in RCU read-side. */ -#define RCU_READ_UNLOCK_NEED_QS (1 << 2) /* RCU core needs CPU response. */ +#define RCU_READ_UNLOCK_NEED_QS (1 << 1) /* RCU core needs CPU response. */ static inline void rcu_copy_process(struct task_struct *p) { diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 9d7d985..01eac49 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -318,7 +318,6 @@ static int rcu_boost(void) t = container_of(tb, struct task_struct, rcu_node_entry); rt_mutex_init_proxy_locked(&mtx, t); t->rcu_boost_mutex = &mtx; - t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED; raw_local_irq_restore(flags); rt_mutex_lock(&mtx); rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ @@ -550,6 +549,9 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) int empty_exp; unsigned long flags; struct list_head *np; +#ifdef CONFIG_RCU_BOOST + struct rt_mutex *rbmp = NULL; +#endif /* #ifdef CONFIG_RCU_BOOST */ int special; /* @@ -615,10 +617,10 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) } #ifdef CONFIG_RCU_BOOST /* Unboost self if was boosted. */ - if (special & RCU_READ_UNLOCK_BOOSTED) { - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED; - rt_mutex_unlock(t->rcu_boost_mutex); + if (t->rcu_boost_mutex != NULL) { + rbmp = t->rcu_boost_mutex; t->rcu_boost_mutex = NULL; + rt_mutex_unlock(rbmp); } #endif /* #ifdef CONFIG_RCU_BOOST */ local_irq_restore(flags); -- 1.7.8