netdev - [PATCH 1/9] softirq: Rewrite softirq processing loop

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Date: Fri, 5 May 2023 19:33:07 +0800
From: Liu Jian <liujian56@...wei.com>
To: <corbet@....net>, <paulmck@...nel.org>, <frederic@...nel.org>,
	<quic_neeraju@...cinc.com>, <joel@...lfernandes.org>,
	<josh@...htriplett.org>, <boqun.feng@...il.com>, <rostedt@...dmis.org>,
	<mathieu.desnoyers@...icios.com>, <jiangshanlai@...il.com>,
	<qiang1.zhang@...el.com>, <jstultz@...gle.com>, <tglx@...utronix.de>,
	<sboyd@...nel.org>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <peterz@...radead.org>,
	<frankwoo@...gle.com>, <Rhinewuwu@...gle.com>
CC: <liujian56@...wei.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <rcu@...r.kernel.org>,
	<netdev@...r.kernel.org>
Subject: [PATCH 1/9] softirq: Rewrite softirq processing loop

From: Peter Zijlstra <peterz@...radead.org>

Simplify the softirq processing loop by using the bitmap APIs

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Liu Jian <liujian56@...wei.com>
---
 kernel/softirq.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 1b725510dd0f..bff5debf6ce6 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -531,9 +531,9 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 	unsigned long old_flags = current->flags;
 	int max_restart = MAX_SOFTIRQ_RESTART;
 	struct softirq_action *h;
+	unsigned long pending;
+	unsigned int vec_nr;
 	bool in_hardirq;
-	__u32 pending;
-	int softirq_bit;
 
 	/*
 	 * Mask out PF_MEMALLOC as the current task context is borrowed for the
@@ -554,15 +554,13 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 
 	local_irq_enable();
 
-	h = softirq_vec;
+	for_each_set_bit(vec_nr, &pending, NR_SOFTIRQS) {
+		unsigned int prev_count;
 
-	while ((softirq_bit = ffs(pending))) {
-		unsigned int vec_nr;
-		int prev_count;
+		__clear_bit(vec_nr, &pending);
 
-		h += softirq_bit - 1;
+		h = softirq_vec + vec_nr;
 
-		vec_nr = h - softirq_vec;
 		prev_count = preempt_count();
 
 		kstat_incr_softirqs_this_cpu(vec_nr);
@@ -576,8 +574,6 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 			       prev_count, preempt_count());
 			preempt_count_set(prev_count);
 		}
-		h++;
-		pending >>= softirq_bit;
 	}
 
 	if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
-- 
2.34.1