From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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, dvhltc@us.ibm.com, niv@us.ibm.com,
tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org,
Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 01/11] rcu: adjust force_quiescent_state() locking, step 1
Date: Mon, 4 Jan 2010 15:09:00 -0800 [thread overview]
Message-ID: <12626465501455-git-send-email-> (raw)
In-Reply-To: <20100104230850.GA22111@linux.vnet.ibm.com>
This causes rnp->lock to be held on entry to force_quiescent_state()'s
switch statement. This is a first step towards prohibiting starting
grace periods while force_quiescent_state() is executing, which will
reduce the number and complexity of races that force_quiescent_state()
is involved in.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 27 ++++++++++++++++++---------
1 files changed, 18 insertions(+), 9 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 53ae959..eae331d 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1204,7 +1204,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
}
if (relaxed &&
(long)(rsp->jiffies_force_qs - jiffies) >= 0)
- goto unlock_ret; /* no emergency and done recently. */
+ goto unlock_fqs_ret; /* no emergency and done recently. */
rsp->n_force_qs++;
spin_lock(&rnp->lock);
lastcomp = rsp->gpnum - 1;
@@ -1213,31 +1213,32 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
if(!rcu_gp_in_progress(rsp)) {
rsp->n_force_qs_ngp++;
spin_unlock(&rnp->lock);
- goto unlock_ret; /* no GP in progress, time updated. */
+ goto unlock_fqs_ret; /* no GP in progress, time updated. */
}
- spin_unlock(&rnp->lock);
switch (signaled) {
case RCU_GP_IDLE:
case RCU_GP_INIT:
+ spin_unlock(&rnp->lock);
break; /* grace period idle or initializing, ignore. */
case RCU_SAVE_DYNTICK:
+ spin_unlock(&rnp->lock);
if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
break; /* So gcc recognizes the dead code. */
/* Record dyntick-idle state. */
if (rcu_process_dyntick(rsp, lastcomp,
dyntick_save_progress_counter))
- goto unlock_ret;
+ goto unlock_fqs_ret;
+ spin_lock(&rnp->lock);
/* fall into next case. */
case RCU_SAVE_COMPLETED:
/* Update state, record completion counter. */
forcenow = 0;
- spin_lock(&rnp->lock);
if (lastcomp + 1 == rsp->gpnum &&
lastcomp == rsp->completed &&
rsp->signaled == signaled) {
@@ -1245,23 +1246,31 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
rsp->completed_fqs = lastcomp;
forcenow = signaled == RCU_SAVE_COMPLETED;
}
- spin_unlock(&rnp->lock);
- if (!forcenow)
+ if (!forcenow) {
+ spin_unlock(&rnp->lock);
break;
+ }
/* fall into next case. */
case RCU_FORCE_QS:
/* Check dyntick-idle state, send IPI to laggarts. */
+ spin_unlock(&rnp->lock);
if (rcu_process_dyntick(rsp, rsp->completed_fqs,
rcu_implicit_dynticks_qs))
- goto unlock_ret;
+ goto unlock_fqs_ret;
/* Leave state in case more forcing is required. */
break;
+
+ default:
+
+ spin_unlock(&rnp->lock);
+ WARN_ON_ONCE(1);
+ break;
}
-unlock_ret:
+unlock_fqs_ret:
spin_unlock_irqrestore(&rsp->fqslock, flags);
}
--
1.5.2.5
next prev parent reply other threads:[~2010-01-04 23:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-04 23:08 [PATCH tip/core/rcu 0/11] rcu: suppress GP start to simplify force_quiescent_state() Paul E. McKenney
2010-01-04 23:09 ` Paul E. McKenney [this message]
2010-01-13 10:24 ` [tip:core/rcu] rcu: Adjust force_quiescent_state() locking, step 1 tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 02/11] rcu: adjust force_quiescent_state() locking, step 2 Paul E. McKenney
2010-01-13 10:25 ` [tip:core/rcu] rcu: Adjust " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 03/11] rcu: prohibit starting new grace periods while forcing quiescent states Paul E. McKenney
2010-01-13 10:25 ` [tip:core/rcu] rcu: Prohibit " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 04/11] rcu: eliminate local variable signaled from force_quiescent_state() Paul E. McKenney
2010-01-13 10:25 ` [tip:core/rcu] rcu: Eliminate " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 05/11] rcu: eliminate local variable lastcomp " Paul E. McKenney
2010-01-13 10:25 ` [tip:core/rcu] rcu: Eliminate " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 06/11] rcu: eliminate second argument of rcu_process_dyntick() Paul E. McKenney
2010-01-13 10:26 ` [tip:core/rcu] rcu: Eliminate " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 07/11] rcu: eliminate rcu_process_dyntick() return value Paul E. McKenney
2010-01-13 10:26 ` [tip:core/rcu] rcu: Eliminate " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 08/11] rcu: remove leg of force_quiescent_state() switch statement Paul E. McKenney
2010-01-13 10:26 ` [tip:core/rcu] rcu: Remove " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 09/11] rcu: remove redundant grace-period check Paul E. McKenney
2010-01-13 10:26 ` [tip:core/rcu] rcu: Remove " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 10/11] rcu: make force_quiescent_state() start grace period if needed Paul E. McKenney
2010-01-13 10:27 ` [tip:core/rcu] rcu: Make " tip-bot for Paul E. McKenney
2010-01-04 23:09 ` [PATCH tip/core/rcu 11/11] rcu: add force_quiescent_state() testing to rcutorture Paul E. McKenney
2010-01-13 10:27 ` [tip:core/rcu] rcu: Add " tip-bot for Paul E. McKenney
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