The patch titled
Subject: rcu: provide a static initializer for hlist_nulls_head
has been added to the -mm mm-nonmm-unstable branch. Its filename is
rcu-provide-a-static-initializer-for-hlist_nulls_head.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/rcu-provide-a-static-initializer-for-hlist_nulls_head.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: rcu: provide a static initializer for hlist_nulls_head
Date: Mon, 3 Feb 2025 16:05:22 +0100
Patch series "ucount: Simplify refcounting with rcuref_t".
I noticed that the atomic_dec_and_lock_irqsave() in put_ucounts() loops
sometimes even during boot. Something like 2-3 iterations but still.
This series replaces the refcounting with rcuref_t and adds a RCU lookup.
This allows a lockless lookup in alloc_ucounts() if the entry is available
and a cmpxchg()less put of the item.
This patch (of 4):
Provide a static initializer for hlist_nulls_head so that it can be used
in statically defined data structures.
Link: https://lkml.kernel.org/r/20250203150525.456525-1-bigeasy@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20250203150525.456525-2-bigeasy@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Acked-by:Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Lai jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Mengen Sun <mengensun@xxxxxxxxxxx>
Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxx>
Cc: "Uladzislau Rezki (Sony)" <urezki@xxxxxxxxx>
Cc: YueHong Wu <yuehongwu@xxxxxxxxxxx>
Cc: Zqiang <qiang.zhang1211@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/list_nulls.h | 1 +
1 file changed, 1 insertion(+)
--- a/include/linux/list_nulls.h~rcu-provide-a-static-initializer-for-hlist_nulls_head
+++ a/include/linux/list_nulls.h
@@ -28,6 +28,7 @@ struct hlist_nulls_node {
#define NULLS_MARKER(value) (1UL | (((long)value) << 1))
#define INIT_HLIST_NULLS_HEAD(ptr, nulls) \
((ptr)->first = (struct hlist_nulls_node *) NULLS_MARKER(nulls))
+#define HLIST_NULLS_HEAD_INIT(nulls) {.first = (struct hlist_nulls_node *)NULLS_MARKER(nulls)}
#define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member)
_
Patches currently in -mm which might be from bigeasy@xxxxxxxxxxxxx are
rcu-provide-a-static-initializer-for-hlist_nulls_head.patch
ucount-replace-get_ucounts_or_wrap-with-atomic_inc_not_zero.patch
ucount-use-rcu-for-ucounts-lookups.patch
ucount-use-rcuref_t-for-reference-counting.patch
