For rcu_bh in UP, rcu_process_callbacks() == a bh == QS == GP
so we can pass rcu_bh-QS and advance GP(and callbacks) in
rcu_process_callbacks().
After doing so, rcu_bh_qs() is useless since its work is handled
by rcu_process_callbacks(). So we make it as empty-function and
raise RCU_SOFTIRQ directly in call_rcu_bh().
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
kernel/rcu/tiny.c | 38 +++++++++++++++++---------------------
1 files changed, 17 insertions(+), 21 deletions(-)
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 805b6d5..f8e19ac 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -72,7 +72,7 @@ static void rcu_idle_enter_common(long long newval)
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
- rcu_sched_qs(); /* implies rcu_bh_inc() */
+ rcu_sched_qs();
barrier();
rcu_dynticks_nesting = newval;
}
@@ -186,49 +186,43 @@ EXPORT_SYMBOL(__rcu_is_watching);
#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
/*
- * Helper function for rcu_sched_qs() and rcu_bh_qs().
+ * Helper function for rcu_sched_ctrlblk and rcu_bh_ctrlblk.
* Also irqs are disabled to avoid confusion due to interrupt handlers
* invoking call_rcu().
*/
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
+ unsigned long flags;
+
+ local_irq_save(flags);
RCU_TRACE(reset_cpu_stall_ticks(rcp));
if (rcp->rcucblist != NULL &&
rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
+ local_irq_restore(flags);
return 1;
}
+ local_irq_restore(flags);
return 0;
}
/*
- * Record an rcu quiescent state. And an rcu_bh quiescent state while we
- * are at it, given that any rcu quiescent state is also an rcu_bh
- * quiescent state. Use "+" instead of "||" to defeat short circuiting.
+ * Record an rcu quiescent state.
*/
void rcu_sched_qs(void)
{
- unsigned long flags;
-
- local_irq_save(flags);
- if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
- rcu_qsctr_help(&rcu_bh_ctrlblk))
+ if (rcu_qsctr_help(&rcu_sched_ctrlblk))
raise_softirq(RCU_SOFTIRQ);
- local_irq_restore(flags);
}
/*
* Record an rcu_bh quiescent state.
+ * Do nothing, since this quiescent state is temporary useless until
+ * RCU_SOFTIRQ, and RCU_SOFTIRQ will really record the quiescent state.
*/
void rcu_bh_qs(void)
{
- unsigned long flags;
-
- local_irq_save(flags);
- if (rcu_qsctr_help(&rcu_bh_ctrlblk))
- raise_softirq(RCU_SOFTIRQ);
- local_irq_restore(flags);
}
/*
@@ -240,12 +234,10 @@ void rcu_bh_qs(void)
void rcu_check_callbacks(int user)
{
RCU_TRACE(check_cpu_stalls());
- if (user)
+ if (user) {
rcu_sched_qs();
- else if (!in_softirq())
- rcu_bh_qs();
- if (user)
rcu_note_voluntary_context_switch(current);
+ }
}
/*
@@ -303,6 +295,9 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
static void rcu_process_callbacks(struct softirq_action *unused)
{
__rcu_process_callbacks(&rcu_sched_ctrlblk);
+
+ /* Here is quiescent state for rcu_bh */
+ rcu_qsctr_help(&rcu_bh_ctrlblk);
__rcu_process_callbacks(&rcu_bh_ctrlblk);
}
@@ -367,6 +362,7 @@ EXPORT_SYMBOL_GPL(call_rcu_sched);
void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
__call_rcu(head, func, &rcu_bh_ctrlblk);
+ raise_softirq(RCU_SOFTIRQ);
}
EXPORT_SYMBOL_GPL(call_rcu_bh);
--
1.7.4.4
--
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