From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A9067E for ; Wed, 2 Nov 2022 02:52:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 358EEC433D6; Wed, 2 Nov 2022 02:52:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667357537; bh=qTuhh6w2GuHxwC6h8CE8WHHd7HSimeGONur4tYkalF4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tPyVo5t9bbMr0sSE9swMiqyDvZ6Qex+hbJFLPJjrL7lzjy0fppY/xgGRdidzNqVaz Nq+c9ZXCrXktq1ItFS2fgsKSS1f5JGT0QRTo2RU0ce8bqctg8Gg0Or6OZrUr5QLlaF kC7ZHGcubZdmEODxeU7nJM0YOOt2GFL/jPmAsLf4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Steven Rostedt , "Paul E. McKenney" , Sasha Levin Subject: [PATCH 6.0 159/240] rcu: Keep synchronize_rcu() from enabling irqs in early boot Date: Wed, 2 Nov 2022 03:32:14 +0100 Message-Id: <20221102022114.977693894@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221102022111.398283374@linuxfoundation.org> References: <20221102022111.398283374@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Paul E. McKenney [ Upstream commit 31d8aaa87fcef1be5932f3813ea369e21bd3b11d ] Making polled RCU grace periods account for expedited grace periods required acquiring the leaf rcu_node structure's lock during early boot, but after rcu_init() was called. This lock is irq-disabled, but the code incorrectly assumes that irqs are always disabled when invoking synchronize_rcu(). The exception is early boot before the scheduler has started, which means that upon return from synchronize_rcu(), irqs will be incorrectly enabled. This commit fixes this bug by using irqsave/irqrestore locking primitives. Fixes: bf95b2bc3e42 ("rcu: Switch polled grace-period APIs to ->gp_seq_polled") Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin --- kernel/rcu/tree.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index eb435941e92f..5b52727dcc1c 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1402,30 +1402,32 @@ static void rcu_poll_gp_seq_end(unsigned long *snap) // where caller does not hold the root rcu_node structure's lock. static void rcu_poll_gp_seq_start_unlocked(unsigned long *snap) { + unsigned long flags; struct rcu_node *rnp = rcu_get_root(); if (rcu_init_invoked()) { lockdep_assert_irqs_enabled(); - raw_spin_lock_irq_rcu_node(rnp); + raw_spin_lock_irqsave_rcu_node(rnp, flags); } rcu_poll_gp_seq_start(snap); if (rcu_init_invoked()) - raw_spin_unlock_irq_rcu_node(rnp); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } // Make the polled API aware of the end of a grace period, but where // caller does not hold the root rcu_node structure's lock. static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap) { + unsigned long flags; struct rcu_node *rnp = rcu_get_root(); if (rcu_init_invoked()) { lockdep_assert_irqs_enabled(); - raw_spin_lock_irq_rcu_node(rnp); + raw_spin_lock_irqsave_rcu_node(rnp, flags); } rcu_poll_gp_seq_end(snap); if (rcu_init_invoked()) - raw_spin_unlock_irq_rcu_node(rnp); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } /* -- 2.35.1