From:   Zqiang <qiang1.zhang@intel.com>
To:     elver@google.com, paulmck@kernel.org
Cc:     linux-kernel@vger.kernel.org, qiang1.zhang@intel.com
Subject: [PATCH v2] rcu, kasan: Record work creation stack trace with interrupts enabled
Date:   Sun, 26 Dec 2021 08:52:04 +0800
Message-Id: <20211226005204.6909-1-qiang1.zhang@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@google.com>
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
---
 v1->v2:
 Make the submitted information clearer.

 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 9b58bae0527a..36bd3f9e57b3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3068,8 +3068,8 @@ 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. */
-- 
2.25.1