linux-kernel - [PATCH 2/7] rcu: limit PREEMPT

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: <20241009165411.3426937-3-ankur.a.arora@oracle.com>
Date: Wed,  9 Oct 2024 09:54:06 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-kernel@...r.kernel.org
Cc: peterz@...radead.org, tglx@...utronix.de, paulmck@...nel.org,
        mingo@...nel.org, bigeasy@...utronix.de, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        vschneid@...hat.com, frederic@...nel.org, ankur.a.arora@...cle.com,
        efault@....de
Subject: [PATCH 2/7] rcu: limit PREEMPT_RCU configurations

PREEMPT_LAZY can be enabled stand-alone or alongside PREEMPT_DYNAMIC
which allows for dynamic switching of preemption models.

The choice of preemptible RCU or not, however, is fixed at compile
time. Given the trade-offs made to have a preemptible RCU, some
configurations which have limited preemption might prefer the
stronger forward-progress guarantees of PREEMPT_RCU=n.

Accordingly, explicitly limit PREEMPT_RCU=y to PREEMPT_DYNAMIC,
PREEMPT, PREEMPT_RT.

This means that (PREEMPT_LAZY=y, PREEMPT_DYNAMIC=n), which selects
PREEMPTION will run with PREEMPT_RCU=n. The combination (PREEMPT_LAZY=y,
PREEMPT_DYNAMIC=y), will run with PREEMPT_RCU=y.

Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 kernel/rcu/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 3e079de0f5b4..1bfe7016724f 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -18,7 +18,7 @@ config TREE_RCU

 config PREEMPT_RCU
 	bool
-	default y if PREEMPTION
+	default y if (PREEMPT || PREEMPT_RT || PREEMPT_DYNAMIC)
 	select TREE_RCU
 	help
 	  This option selects the RCU implementation that is
-- 
2.43.5