From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH tip/core/rcu 04/12] rcu: Allow rcu_read_unlock_special() to raise_softirq() if in_irq()
Date: Thu, 30 May 2019 07:52:21 -0700 [thread overview]
Message-ID: <20190530145229.29565-4-paulmck@linux.ibm.com> (raw)
In-Reply-To: <20190530145204.GA28526@linux.ibm.com>
When running in an interrupt handler, raise_softirq() and
raise_softirq_irqoff() have extremely low overhead: They simply set a
bit in a per-CPU mask, which is checked upon exit from that interrupt
handler. Therefore, if rcu_read_unlock_special() is invoked within an
interrupt handler and RCU_SOFTIRQ is in use, this commit make use of
raise_softirq_irqoff() even if there is no expedited grace period in
flight and even if this is not a nohz_full CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
kernel/rcu/tree_plugin.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index d15cdab6aeb4..e1005f5e8094 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -615,7 +615,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
(rdp->grpmask & rnp->expmask) ||
tick_nohz_full_cpu(rdp->cpu);
// Need to defer quiescent state until everything is enabled.
- if (exp && irqs_were_disabled && use_softirq &&
+ if ((exp || in_irq()) && irqs_were_disabled && use_softirq &&
(in_irq() || !t->rcu_read_unlock_special.b.deferred_qs)) {
// Using softirq, safe to awaken, and we get
// no help from enabling irqs, unlike bh/preempt.
--
2.17.1
next prev parent reply other threads:[~2019-05-30 14:53 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-30 14:52 [PATCH tip/core/rcu 0/12] Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 01/12] rcu: Enable elimination of Tree-RCU softirq processing Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 02/12] rcu: Check for wakeup-safe conditions in rcu_read_unlock_special() Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 03/12] rcu: Only do rcu_read_unlock_special() wakeups if expedited Paul E. McKenney
2019-05-30 14:52 ` Paul E. McKenney [this message]
2019-05-30 14:52 ` [PATCH tip/core/rcu 05/12] rcu: Use irq_work to get scheduler's attention in clean context Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 06/12] rcu: Inline invoke_rcu_callbacks() into its sole remaining caller Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 07/12] rcu: Avoid self-IPI in sync_rcu_exp_select_node_cpus() Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 08/12] rcu: Avoid self-IPI in sync_sched_exp_online_cleanup() Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 09/12] lockdep: Add assertion to check if in an interrupt Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 10/12] rcu: Add checks for dynticks counters in rcu_is_cpu_rrupt_from_idle() Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 11/12] rcu: Rename rcu_data's ->deferred_qs to ->exp_deferred_qs Paul E. McKenney
2019-05-30 14:52 ` [PATCH tip/core/rcu 12/12] rcu: Remove unused rdp local from synchronize_rcu_expedited() Paul E. McKenney
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