On 9/15/25 9:47 AM, pengdonglin wrote:
From: pengdonglin <pengdong...@xiaomi.com>
Per Documentation/RCU/rcu_dereference.rst [1], since Linux 4.20's RCU
consolidation [2][3], RCU read-side critical sections include:
- Explicit rcu_read_lock()
- BH/interrupt/preemption-disabling regions
- Spinlock critical sections (including CONFIG_PREEMPT_RT kernels [4])
Thus, explicit rcu_read_lock()/unlock() calls within spin_lock*() regions are
redundant.
This patch removes them, simplifying locking semantics while preserving RCU
protection.
[1]
https://elixir.bootlin.com/linux/v6.17-rc5/source/Documentation/RCU/rcu_dereference.rst#L407
[2] https://lore.kernel.org/lkml/20180829222021.ga29...@linux.vnet.ibm.com/
[3] https://lwn.net/Articles/777036/
[4]
https://lore.kernel.org/lkml/6435833a-bdcb-4114-b29d-28b7f436d47d@paulmck-laptop/
Cc: Waiman Long <long...@redhat.com>
Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
Cc: Hillf Danton <hdan...@sina.com>
Cc: Paul E. McKenney <paul...@kernel.org>
Signed-off-by: pengdonglin <pengdong...@xiaomi.com>
Signed-off-by: pengdonglin <dolinux.p...@gmail.com>
---
Changes in v2:
- Clarified commit message to prevent accidental backport to older kernels
- Added lockdep_is_held() to avoid false positives
---
drivers/acpi/apei/ghes.c | 2 --
drivers/gpu/drm/i915/gt/intel_ring_submission.c | 2 --
drivers/net/amt.c | 8 --------
drivers/net/bonding/bond_3ad.c | 2 --
drivers/net/wireless/ath/ath9k/xmit.c | 2 --
drivers/s390/crypto/pkey_base.c | 3 ---
fs/aio.c | 6 ++----
fs/nfs/callback_proc.c | 2 --
fs/nfs/nfs4state.c | 2 --
fs/nfs/pnfs.c | 9 ---------
fs/nfs/pnfs_dev.c | 4 ----
ipc/msg.c | 1 -
ipc/sem.c | 1 -
ipc/shm.c | 1 -
ipc/util.c | 2 --
kernel/cgroup/cgroup.c | 2 --
kernel/cgroup/cpuset.c | 6 ------
kernel/cgroup/debug.c | 4 ----
net/mac80211/cfg.c | 2 --
net/mac80211/debugfs.c | 2 --
net/mac80211/debugfs_netdev.c | 2 --
net/mac80211/debugfs_sta.c | 2 --
net/mac80211/sta_info.c | 2 --
net/ncsi/ncsi-manage.c | 2 --
security/yama/yama_lsm.c | 4 ----
25 files changed, 2 insertions(+), 73 deletions(-)
...
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 27adb04df675..9b7e8e8e9411 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -4073,7 +4073,6 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct
cpumask *pmask)
struct cpuset *cs;
spin_lock_irqsave(&callback_lock, flags);
- rcu_read_lock();
cs = task_cs(tsk);
if (cs != &top_cpuset)
@@ -4095,7 +4094,6 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct
cpumask *pmask)
cpumask_copy(pmask, possible_mask);
}
- rcu_read_unlock();
spin_unlock_irqrestore(&callback_lock, flags);
}
@@ -4168,9 +4166,7 @@ nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
unsigned long flags;
spin_lock_irqsave(&callback_lock, flags);
- rcu_read_lock();
guarantee_online_mems(task_cs(tsk), &mask);
- rcu_read_unlock();
spin_unlock_irqrestore(&callback_lock, flags);
return mask;
@@ -4265,10 +4261,8 @@ bool cpuset_current_node_allowed(int node, gfp_t
gfp_mask)
/* Not hardwall and node outside mems_allowed: scan up cpusets */
spin_lock_irqsave(&callback_lock, flags);
- rcu_read_lock();
cs = nearest_hardwall_ancestor(task_cs(current));
allowed = node_isset(node, cs->mems_allowed);
- rcu_read_unlock();
spin_unlock_irqrestore(&callback_lock, flags);
return allowed;
For cpuset,
Acked-by: Waiman Long <long...@redhat.com>
