linux-kernel - [PATCH V7 3/4] softirq: Rewrite softirq processing loop

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Date:   Tue, 15 Sep 2020 19:56:08 +0800
From:   qianjun.kernel@...il.com
To:     tglx@...utronix.de, peterz@...radead.org, will@...nel.org,
        luto@...nel.org, linux-kernel@...r.kernel.org
Cc:     laoar.shao@...il.com, qais.yousef@....com, urezki@...il.com,
        jun qian <qianjun.kernel@...il.com>
Subject: [PATCH V7 3/4] softirq: Rewrite softirq processing loop

From: jun qian <qianjun.kernel@...il.com>

Simplify the softirq processing loop by using the bitmap APIs

Signed-off-by: jun qian <qianjun.kernel@...il.com>
---
 kernel/softirq.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 5a627cd..cbb59b5 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -260,9 +260,9 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 	unsigned long old_flags = current->flags;
 	unsigned 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
@@ -283,15 +283,13 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 
 	local_irq_enable();
 
-	h = softirq_vec;
-
-	while ((softirq_bit = ffs(pending))) {
-		unsigned int vec_nr;
+	for_each_set_bit(vec_nr, &pending, NR_SOFTIRQS) {
 		int prev_count;
 
-		h += softirq_bit - 1;
+		__clear_bit(vec_nr, &pending);
+
+		h = softirq_vec + vec_nr;
 
-		vec_nr = h - softirq_vec;
 		prev_count = preempt_count();
 
 		kstat_incr_softirqs_this_cpu(vec_nr);
@@ -305,8 +303,6 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 			       prev_count, preempt_count());
 			preempt_count_set(prev_count);
 		}
-		h++;
-		pending >>= softirq_bit;
 	}
 
 	if (__this_cpu_read(ksoftirqd) == current)
-- 
1.8.3.1