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Message-Id: <20180829225405.7275-2-paulmck@linux.vnet.ibm.com>
Date: Wed, 29 Aug 2018 15:53:43 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 02/24] rcu: Pull rcu_gp_kthread() FQS loop into separate function
The rcu_gp_kthread() function is long and deeply indented, so this
commit pulls the loop that repeatedly invokes rcu_gp_fqs() into a new
rcu_gp_fqs_loop() function.
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
kernel/rcu/tree.c | 125 ++++++++++++++++++++++++----------------------
1 file changed, 66 insertions(+), 59 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 35a4346c7cce..bfb6b15bc27c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1975,6 +1975,71 @@ static void rcu_gp_fqs(bool first_time)
}
}
+/*
+ * Loop doing repeated quiescent-state forcing until the grace period ends.
+ */
+static void rcu_gp_fqs_loop(void)
+{
+ bool first_gp_fqs;
+ int gf;
+ unsigned long j;
+ int ret;
+ struct rcu_node *rnp = rcu_get_root();
+
+ first_gp_fqs = true;
+ j = jiffies_till_first_fqs;
+ ret = 0;
+ for (;;) {
+ if (!ret) {
+ rcu_state.jiffies_force_qs = jiffies + j;
+ WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
+ jiffies + 3 * j);
+ }
+ trace_rcu_grace_period(rcu_state.name,
+ READ_ONCE(rcu_state.gp_seq),
+ TPS("fqswait"));
+ rcu_state.gp_state = RCU_GP_WAIT_FQS;
+ ret = swait_event_idle_timeout_exclusive(
+ rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j);
+ rcu_state.gp_state = RCU_GP_DOING_FQS;
+ /* Locking provides needed memory barriers. */
+ /* If grace period done, leave loop. */
+ if (!READ_ONCE(rnp->qsmask) &&
+ !rcu_preempt_blocked_readers_cgp(rnp))
+ break;
+ /* If time for quiescent-state forcing, do it. */
+ if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) ||
+ (gf & RCU_GP_FLAG_FQS)) {
+ trace_rcu_grace_period(rcu_state.name,
+ READ_ONCE(rcu_state.gp_seq),
+ TPS("fqsstart"));
+ rcu_gp_fqs(first_gp_fqs);
+ first_gp_fqs = false;
+ trace_rcu_grace_period(rcu_state.name,
+ READ_ONCE(rcu_state.gp_seq),
+ TPS("fqsend"));
+ cond_resched_tasks_rcu_qs();
+ WRITE_ONCE(rcu_state.gp_activity, jiffies);
+ ret = 0; /* Force full wait till next FQS. */
+ j = jiffies_till_next_fqs;
+ } else {
+ /* Deal with stray signal. */
+ cond_resched_tasks_rcu_qs();
+ WRITE_ONCE(rcu_state.gp_activity, jiffies);
+ WARN_ON(signal_pending(current));
+ trace_rcu_grace_period(rcu_state.name,
+ READ_ONCE(rcu_state.gp_seq),
+ TPS("fqswaitsig"));
+ ret = 1; /* Keep old FQS timing. */
+ j = jiffies;
+ if (time_after(jiffies, rcu_state.jiffies_force_qs))
+ j = 1;
+ else
+ j = rcu_state.jiffies_force_qs - j;
+ }
+ }
+}
+
/*
* Clean up after the old grace period.
*/
@@ -2065,12 +2130,6 @@ static void rcu_gp_cleanup(void)
*/
static int __noreturn rcu_gp_kthread(void *unused)
{
- bool first_gp_fqs;
- int gf;
- unsigned long j;
- int ret;
- struct rcu_node *rnp = rcu_get_root();
-
rcu_bind_gp_kthread();
for (;;) {
@@ -2096,59 +2155,7 @@ static int __noreturn rcu_gp_kthread(void *unused)
}
/* Handle quiescent-state forcing. */
- first_gp_fqs = true;
- j = jiffies_till_first_fqs;
- ret = 0;
- for (;;) {
- if (!ret) {
- rcu_state.jiffies_force_qs = jiffies + j;
- WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
- jiffies + 3 * j);
- }
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
- TPS("fqswait"));
- rcu_state.gp_state = RCU_GP_WAIT_FQS;
- ret = swait_event_idle_timeout_exclusive(rcu_state.gp_wq,
- rcu_gp_fqs_check_wake(&gf), j);
- rcu_state.gp_state = RCU_GP_DOING_FQS;
- /* Locking provides needed memory barriers. */
- /* If grace period done, leave loop. */
- if (!READ_ONCE(rnp->qsmask) &&
- !rcu_preempt_blocked_readers_cgp(rnp))
- break;
- /* If time for quiescent-state forcing, do it. */
- if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) ||
- (gf & RCU_GP_FLAG_FQS)) {
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
- TPS("fqsstart"));
- rcu_gp_fqs(first_gp_fqs);
- first_gp_fqs = false;
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
- TPS("fqsend"));
- cond_resched_tasks_rcu_qs();
- WRITE_ONCE(rcu_state.gp_activity, jiffies);
- ret = 0; /* Force full wait till next FQS. */
- j = jiffies_till_next_fqs;
- } else {
- /* Deal with stray signal. */
- cond_resched_tasks_rcu_qs();
- WRITE_ONCE(rcu_state.gp_activity, jiffies);
- WARN_ON(signal_pending(current));
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
- TPS("fqswaitsig"));
- ret = 1; /* Keep old FQS timing. */
- j = jiffies;
- if (time_after(jiffies,
- rcu_state.jiffies_force_qs))
- j = 1;
- else
- j = rcu_state.jiffies_force_qs - j;
- }
- }
+ rcu_gp_fqs_loop();
/* Handle grace-period end. */
rcu_state.gp_state = RCU_GP_CLEANUP;
--
2.17.1
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