From b5aa859fd82a74cdebfdfac33a14f0eca675c2d4 Mon Sep 17 00:00:00 2001
From: Zhouyi Zhou <zhouzhouyi@gmail.com>
Date: Mon, 26 Jul 2021 05:43:33 +0800
Subject: [PATCH] rcu: Fix undefined Kconfig macros
References: bnc#1189998 (PREEMPT_RT prerequisite backports)
Patch-mainline: v5.16-rc1
Git-commit: 3ac858785231e2573d2964950738aac087ebf30c
Invoking scripts/checkkconfigsymbols.py in the Linux-kernel source tree
located the following issues:
1. TREE_PREEMPT_RCU
Referencing files: arch/sh/configs/sdk7786_defconfig
It should now be CONFIG_PREEMPT_RCU. Except that the CONFIG_PREEMPT=y in
that same file implies CONFIG_PREEMPT_RCU=y. Therefore, delete the
CONFIG_TREE_PREEMPT_RCU=y line.
The reason is as follows:
In kernel/rcu/Kconfig, we have
config PREEMPT_RCU
bool
default y if PREEMPTION
https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt says,
"The default value is only assigned to the config symbol if no other value
was set by the user (via the input prompt above)."
there is no prompt in config PREEMPT_RCU entry, so we are guaranteed to
get CONFIG_PREEMPT_RCU=y when CONFIG_PREEMPT is present.
2. RCU_CPU_STALL_INFO
Referencing files: arch/xtensa/configs/nommu_kc705_defconfig
The old Kconfig option RCU_CPU_STALL_INFO was removed by commit
75c27f119b64 ("rcu: Remove CONFIG_RCU_CPU_STALL_INFO"), and the kernel
now acts as if this Kconfig option was unconditionally enabled.
3. RCU_NOCB_CPU_ALL
Referencing files:
Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst
This is an old snapshot of the code. I update this from the real
rcu_prepare_for_idle() function in kernel/rcu/tree_plugin.h.
This change was tested by invoking "make htmldocs".
4. RCU_TORTURE_TESTS
Referencing files: kernel/rcu/rcutorture.c
Forward-progress checking conflicts with CPU-stall testing, so we should
complain at "modprobe rcutorture" when both are enabled.
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
.../Memory-Ordering/Tree-RCU-Memory-Ordering.rst | 69 ++++++++++------------
arch/sh/configs/sdk7786_defconfig | 1 -
arch/xtensa/configs/nommu_kc705_defconfig | 1 -
kernel/rcu/rcutorture.c | 2 +-
4 files changed, 33 insertions(+), 40 deletions(-)
diff --git a/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst
index 11cdab037bff..0c4b730bffd7 100644
--- a/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst
+++ b/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst
@@ -173,49 +173,44 @@ shown below, which is one of several functions that enforce ordering of
1 static void rcu_prepare_for_idle(void)
2 {
3 bool needwake;
- 4 struct rcu_data *rdp;
- 5 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
- 6 struct rcu_node *rnp;
- 7 struct rcu_state *rsp;
- 8 int tne;
- 9
- 10 if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) ||
- 11 rcu_is_nocb_cpu(smp_processor_id()))
- 12 return;
+ 4 struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ 5 struct rcu_node *rnp;
+ 6 int tne;
+ 7
+ 8 lockdep_assert_irqs_disabled();
+ 9 if (rcu_rdp_is_offloaded(rdp))
+ 10 return;
+ 11
+ 12 /* Handle nohz enablement switches conservatively. */
13 tne = READ_ONCE(tick_nohz_active);
- 14 if (tne != rdtp->tick_nohz_enabled_snap) {
- 15 if (rcu_cpu_has_callbacks(NULL))
- 16 invoke_rcu_core();
- 17 rdtp->tick_nohz_enabled_snap = tne;
+ 14 if (tne != rdp->tick_nohz_enabled_snap) {
+ 15 if (!rcu_segcblist_empty(&rdp->cblist))
+ 16 invoke_rcu_core(); /* force nohz to see update. */
+ 17 rdp->tick_nohz_enabled_snap = tne;
18 return;
- 19 }
+ 19 }
20 if (!tne)
21 return;
- 22 if (rdtp->all_lazy &&
- 23 rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) {
- 24 rdtp->all_lazy = false;
- 25 rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;
- 26 invoke_rcu_core();
- 27 return;
- 28 }
- 29 if (rdtp->last_accelerate == jiffies)
- 30 return;
- 31 rdtp->last_accelerate = jiffies;
- 32 for_each_rcu_flavor(rsp) {
- 33 rdp = this_cpu_ptr(rsp->rda);
- 34 if (rcu_segcblist_pend_cbs(&rdp->cblist))
- 35 continue;
- 36 rnp = rdp->mynode;
- 37 raw_spin_lock_rcu_node(rnp);
- 38 needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
- 39 raw_spin_unlock_rcu_node(rnp);
- 40 if (needwake)
- 41 rcu_gp_kthread_wake(rsp);
- 42 }
- 43 }
+ 22
+ 23 /*
+ 24 * If we have not yet accelerated this jiffy, accelerate all
+ 25 * callbacks on this CPU.
+ 26 */
+ 27 if (rdp->last_accelerate == jiffies)
+ 28 return;
+ 29 rdp->last_accelerate = jiffies;
+ 30 if (rcu_segcblist_pend_cbs(&rdp->cblist)) {
+ 31 rnp = rdp->mynode;
+ 32 raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
+ 33 needwake = rcu_accelerate_cbs(rnp, rdp);
+ 34 raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
+ 35 if (needwake)
+ 36 rcu_gp_kthread_wake();
+ 37 }
+ 38 }
But the only part of ``rcu_prepare_for_idle()`` that really matters for
-this discussion are lines 37–39. We will therefore abbreviate this
+this discussion are lines 32–34. We will therefore abbreviate this
function as follows:
.. kernel-figure:: rcu_node-lock.svg
diff --git a/arch/sh/configs/sdk7786_defconfig b/arch/sh/configs/sdk7786_defconfig
index f776a1d0d277..a8662b6927ec 100644
--- a/arch/sh/configs/sdk7786_defconfig
+++ b/arch/sh/configs/sdk7786_defconfig
@@ -5,7 +5,6 @@ CONFIG_BSD_PROCESS_ACCT=y
CONFIG_BSD_PROCESS_ACCT_V3=y
CONFIG_AUDIT=y
CONFIG_AUDITSYSCALL=y
-CONFIG_TREE_PREEMPT_RCU=y
CONFIG_RCU_TRACE=y
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
diff --git a/arch/xtensa/configs/nommu_kc705_defconfig b/arch/xtensa/configs/nommu_kc705_defconfig
index 88b2e222d4bf..fcb620ef3799 100644
--- a/arch/xtensa/configs/nommu_kc705_defconfig
+++ b/arch/xtensa/configs/nommu_kc705_defconfig
@@ -119,7 +119,6 @@ CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_ATOMIC_SLEEP=y
CONFIG_STACKTRACE=y
-# CONFIG_RCU_CPU_STALL_INFO is not set
CONFIG_RCU_TRACE=y
# CONFIG_FTRACE is not set
# CONFIG_LD_NO_RELAX is not set
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 968696ace8f3..4b012e1b6aa8 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2473,7 +2473,7 @@ static int __init rcu_torture_fwd_prog_init(void)
}
if (stall_cpu > 0) {
VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
- if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
+ if (IS_MODULE(CONFIG_RCU_TORTURE_TEST))
return -EINVAL; /* In module, can fail back to user. */
WARN_ON(1); /* Make sure rcutorture notices conflict. */
return 0;