linux-kernel - [RFC PATCH 08/12] rcu: Flush bypass before setting SEGCBLIST_SOFTIRQ

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200921124351.24035-9-frederic@kernel.org>
Date:   Mon, 21 Sep 2020 14:43:47 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Paul E . McKenney" <paulmck@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>
Subject: [RFC PATCH 08/12] rcu: Flush bypass before setting SEGCBLIST_SOFTIRQ_ONLY

Make sure to handle the pending bypass queue before we switch to the
final de-offload state. We'll have to be careful and later set
SEGCBLIST_SOFTIRQ_ONLY before re-enabling again IRQs, or new bypass
callbacks could be queued in the meantine.

Inspired-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Lai Jiangshan <jiangshanlai@...il.com>
Cc: Joel Fernandes <joel@...lfernandes.org>
---
 kernel/rcu/tree_plugin.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 3361bd351f3b..cee15841c178 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2302,11 +2302,17 @@ static void __rcu_nocb_rdp_deoffload(struct rcu_data *rdp)
 			      !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
 							SEGCBLIST_KTHREAD_GP));
 
+	rcu_nocb_lock_irqsave(rdp, flags);
 	/* Make sure nocb timer won't stay around */
-	rcu_nocb_lock_irqsave(rdp, flags);
 	WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF);
-	rcu_nocb_unlock_irqrestore(rdp, flags);
 	del_timer_sync(&rdp->nocb_timer);
+	/*
+	 * Flush bypass. While IRQs are disabled and once we set
+	 * SEGCBLIST_SOFTIRQ_ONLY, no callback is supposed to be
+	 * enqueued on bypass.
+	 */
+	rcu_nocb_flush_bypass(rdp, NULL, jiffies);
+	rcu_nocb_unlock_irqrestore(rdp, flags);
 }
 
 static long rcu_nocb_rdp_deoffload(void *arg)
-- 
2.28.0