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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-01-04 15:09:06 -0800
committerIngo Molnar <mingo@elte.hu>2010-01-13 09:06:03 +0100
commit0f10dc826646134dce3e5751512b87d30f3903e4 (patch)
tree6d377b3714889a0ab148166a33105b3be14be0c1 /kernel/rcutree.c
parenteb1ba45f1e7f6e626fefc063b340c7cbec9bd8c7 (diff)
rcu: Eliminate rcu_process_dyntick() return value
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> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <12626465501857-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c17
1 files changed, 6 insertions, 11 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index c7d00700fc4e..e4971192fa9c 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. */