linux-kernel - [PATCH rcu 5/9] kasan: Record work creation stack trace with interrupts enabled

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Message-Id: <20220204230805.4193767-5-paulmck@kernel.org>
Date:   Fri,  4 Feb 2022 15:08:01 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, Zqiang <qiang1.zhang@...el.com>,
        Marco Elver <elver@...gle.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 5/9] kasan: Record work creation stack trace with interrupts enabled

From: Zqiang <qiang1.zhang@...el.com>

Recording the work creation stack trace for KASAN reports in
call_rcu() is expensive, due to unwinding the stack, but also
due to acquiring depot_lock inside stackdepot (which may be contended).
Because calling kasan_record_aux_stack_noalloc() does not require
interrupts to already be disabled, this may unnecessarily extend
the time with interrupts disabled.

Therefore, move calling kasan_record_aux_stack() before the section
with interrupts disabled.

Acked-by: Marco Elver <elver@...gle.com>
Signed-off-by: Zqiang <qiang1.zhang@...el.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index f1bb7ccc00847..ca8d7dd026eeb 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3060,8 +3060,8 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
 	}
 	head->func = func;
 	head->next = NULL;
-	local_irq_save(flags);
 	kasan_record_aux_stack_noalloc(head);
+	local_irq_save(flags);
 	rdp = this_cpu_ptr(&rcu_data);
 
 	/* Add the callback to our list. */
-- 
2.31.1.189.g2e36527f23