linux-kernel - [PATCH] lib/flex_proportions.c: Remove local_irq_ops in fprop_new

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Date:   Sat,  4 Jun 2022 21:15:02 +0800
From:   wuchi <wuchi.zero@...il.com>
To:     jack@...e.cz, hch@....de
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: [PATCH] lib/flex_proportions.c: Remove local_irq_ops in fprop_new_period()

The commit <e78d4833c03e28> (lib: Fix possible deadlock in flexible
proportion code) adds the local_irq_ops because percpu_counter_{sum
|add} ops'lock can cause deadlock by interrupts. Now percpu_counter
_{sum|add} ops use raw_spin_(un)lock_irq*, so revert the commit and
resolve the conflict.

Signed-off-by: wuchi <wuchi.zero@...il.com>
---
 lib/flex_proportions.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
index 53e7eb1dd76c..05cccbcf1661 100644
--- a/lib/flex_proportions.c
+++ b/lib/flex_proportions.c
@@ -63,18 +63,13 @@ void fprop_global_destroy(struct fprop_global *p)
  */
 bool fprop_new_period(struct fprop_global *p, int periods)
 {
-	s64 events;
-	unsigned long flags;
+	s64 events = percpu_counter_sum(&p->events);
 
-	local_irq_save(flags);
-	events = percpu_counter_sum(&p->events);
 	/*
 	 * Don't do anything if there are no events.
 	 */
-	if (events <= 1) {
-		local_irq_restore(flags);
+	if (events <= 1)
 		return false;
-	}
 	write_seqcount_begin(&p->sequence);
 	if (periods < 64)
 		events -= events >> periods;
@@ -82,7 +77,6 @@ bool fprop_new_period(struct fprop_global *p, int periods)
 	percpu_counter_add(&p->events, -events);
 	p->period += periods;
 	write_seqcount_end(&p->sequence);
-	local_irq_restore(flags);
 
 	return true;
 }
-- 
2.20.1