linux-kernel - [PATCH v2 16/17] delay_acct: Mark task's delays->lock as terminal spinlock

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Date:   Mon, 19 Nov 2018 13:55:25 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v2 16/17] delay_acct: Mark task's delays->lock as terminal spinlock

By making task's delays->lock a terminal spinlock, it reduces the
lockdep overhead when this lock is used.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/delayacct.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 2a12b98..49dd8d3 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -43,8 +43,10 @@ void delayacct_init(void)
 void __delayacct_tsk_init(struct task_struct *tsk)
 {
 	tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
-	if (tsk->delays)
+	if (tsk->delays) {
 		raw_spin_lock_init(&tsk->delays->lock);
+		lockdep_set_terminal_class(&tsk->delays->lock);
+	}
 }
 
 /*
-- 
1.8.3.1