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 RFC tip/core/rcu 07/18] rcu: eliminate rcu_process_dyntick() return value
Date: Tue, 15 Dec 2009 15:02:30 -0800 [thread overview]
Message-ID: <1260918161972-git-send-email-> (raw)
In-Reply-To: <20091215230213.GA9093@linux.vnet.ibm.com>
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Proposed for 2.6.34, not for inclusion.
Because a new grace period cannot start while we are executing within the
force_quiescent_state() function's switch statement, if any test within
that switch statement or within any function called from that switch
statement shows that the current grace period has ended, we can safely
re-do that test any time before we leave the switch statement. This
means that we no longer need a return value from rcu_process_dyntick(),
as we can simply invoke rcu_gp_in_progress() to check whether the old
grace period has finished -- there is no longer any need to worry about
whether or not a new grace period has been started.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 17 ++++++-----------
1 files changed, 6 insertions(+), 11 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index c7d0070..e497119 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1144,11 +1144,9 @@ void rcu_check_callbacks(int cpu, int user)
/*
* Scan the leaf rcu_node structures, processing dyntick state for any that
* have not yet encountered a quiescent state, using the function specified.
- * Returns 1 if the current grace period ends while scanning (possibly
- * because we made it end).
*/
-static int rcu_process_dyntick(struct rcu_state *rsp,
- int (*f)(struct rcu_data *))
+static void rcu_process_dyntick(struct rcu_state *rsp,
+ int (*f)(struct rcu_data *))
{
unsigned long bit;
int cpu;
@@ -1161,7 +1159,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp,
spin_lock_irqsave(&rnp->lock, flags);
if (rnp->completed != rsp->gpnum - 1) {
spin_unlock_irqrestore(&rnp->lock, flags);
- return 1;
+ return;
}
if (rnp->qsmask == 0) {
spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1181,7 +1179,6 @@ static int rcu_process_dyntick(struct rcu_state *rsp,
}
spin_unlock_irqrestore(&rnp->lock, flags);
}
- return 0;
}
/*
@@ -1193,7 +1190,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
unsigned long flags;
struct rcu_node *rnp = rcu_get_root(rsp);
u8 forcenow;
- u8 gpdone;
if (!rcu_gp_in_progress(rsp))
return; /* No grace period in progress, nothing to force. */
@@ -1226,10 +1222,9 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
break; /* So gcc recognizes the dead code. */
/* Record dyntick-idle state. */
- gpdone = rcu_process_dyntick(rsp,
- dyntick_save_progress_counter);
+ rcu_process_dyntick(rsp, dyntick_save_progress_counter);
spin_lock(&rnp->lock); /* irqs already disabled */
- if (gpdone)
+ if (!rcu_gp_in_progress(rsp))
break;
/* fall into next case. */
@@ -1249,7 +1244,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
/* Check dyntick-idle state, send IPI to laggarts. */
spin_unlock(&rnp->lock); /* irqs remain disabled */
- gpdone = rcu_process_dyntick(rsp, rcu_implicit_dynticks_qs);
+ rcu_process_dyntick(rsp, rcu_implicit_dynticks_qs);
/* Leave state in case more forcing is required. */
--
1.5.2.5
next prev parent reply other threads:[~2009-12-15 23:09 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-15 23:02 [PATCH RFC tip/core/rcu 0/18] rcu: simplify race conditions, add checking Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 01/18] rcu: adjust force_quiescent_state() locking, step 1 Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 02/18] rcu: adjust force_quiescent_state() locking, step 2 Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 03/18] rcu: prohibit starting new grace periods while forcing quiescent states Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 04/18] rcu: eliminate local variable signaled from force_quiescent_state() Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 05/18] rcu: eliminate local variable lastcomp " Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 06/18] rcu: eliminate second argument of rcu_process_dyntick() Paul E. McKenney
2009-12-15 23:02 ` Paul E. McKenney [this message]
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 08/18] rcu: remove leg of force_quiescent_state() switch statement Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 09/18] rcu: remove redundant grace-period check Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 10/18] rcu: make force_quiescent_state() start grace period if needed Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 11/18] rcu: add force_quiescent_state() testing to rcutorture Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 12/18] rcu: make MAINTAINERS file match new RCU reality Paul E. McKenney
2009-12-16 0:53 ` Josh Triplett
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 13/18] rcu: add debug check for too many rcu_read_unlock() Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 14/18] rcu: lockdep check for exiting to user space as RCU reader Paul E. McKenney
2009-12-16 10:24 ` Peter Zijlstra
2009-12-16 15:11 ` Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 15/18] rcu: give different levels of the rcu_node hierarchy distinct lockdep names Paul E. McKenney
2009-12-16 0:59 ` Josh Triplett
2009-12-16 1:59 ` Paul E. McKenney
2009-12-16 10:26 ` Peter Zijlstra
2009-12-16 10:33 ` Peter Zijlstra
2009-12-16 15:13 ` Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 16/18] rcu: make lockdep aware of SRCU read-side critical sections Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 17/18] rcu: Provide different lockdep classes for each flavor of RCU Paul E. McKenney
2009-12-15 23:02 ` [PATCH RFC tip/core/rcu 18/18] rcu: add primitives to check for RCU read-side critical sections Paul E. McKenney
2009-12-16 1:04 ` Josh Triplett
2009-12-16 2:08 ` Paul E. McKenney
2009-12-16 10:31 ` Peter Zijlstra
2009-12-16 15:18 ` Paul E. McKenney
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