+ kprobes-freelisth-removed.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kprobes: freelist.h removed
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kprobes-freelisth-removed.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kprobes-freelisth-removed.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: wuqiang <wuqiang.matt@bytedance.com>
Subject: kprobes: freelist.h removed
Date: Sun, 6 Nov 2022 13:34:41 +0800

This patch will remove freelist.h from kernel source tree, since the only
use cases (kretprobe and rethook) are converted to objpool.

Link: https://lkml.kernel.org/r/20221106053441.103199-5-wuqiang.matt@bytedance.com
Signed-off-by: wuqiang <wuqiang.matt@bytedance.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sander Vanheule <sander@svanheule.net>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/freelist.h |  129 -------------------------------------
 1 file changed, 129 deletions(-)

--- a/include/linux/freelist.h
+++ /dev/null
@@ -1,129 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause */
-#ifndef FREELIST_H
-#define FREELIST_H
-
-#include <linux/atomic.h>
-
-/*
- * Copyright: cameron@moodycamel.com
- *
- * A simple CAS-based lock-free free list. Not the fastest thing in the world
- * under heavy contention, but simple and correct (assuming nodes are never
- * freed until after the free list is destroyed), and fairly speedy under low
- * contention.
- *
- * Adapted from: https://moodycamel.com/blog/2014/solving-the-aba-problem-for-lock-free-free-lists
- */
-
-struct freelist_node {
-	atomic_t		refs;
-	struct freelist_node	*next;
-};
-
-struct freelist_head {
-	struct freelist_node	*head;
-};
-
-#define REFS_ON_FREELIST 0x80000000
-#define REFS_MASK	 0x7FFFFFFF
-
-static inline void __freelist_add(struct freelist_node *node, struct freelist_head *list)
-{
-	/*
-	 * Since the refcount is zero, and nobody can increase it once it's
-	 * zero (except us, and we run only one copy of this method per node at
-	 * a time, i.e. the single thread case), then we know we can safely
-	 * change the next pointer of the node; however, once the refcount is
-	 * back above zero, then other threads could increase it (happens under
-	 * heavy contention, when the refcount goes to zero in between a load
-	 * and a refcount increment of a node in try_get, then back up to
-	 * something non-zero, then the refcount increment is done by the other
-	 * thread) -- so if the CAS to add the node to the actual list fails,
-	 * decrese the refcount and leave the add operation to the next thread
-	 * who puts the refcount back to zero (which could be us, hence the
-	 * loop).
-	 */
-	struct freelist_node *head = READ_ONCE(list->head);
-
-	for (;;) {
-		WRITE_ONCE(node->next, head);
-		atomic_set_release(&node->refs, 1);
-
-		if (!try_cmpxchg_release(&list->head, &head, node)) {
-			/*
-			 * Hmm, the add failed, but we can only try again when
-			 * the refcount goes back to zero.
-			 */
-			if (atomic_fetch_add_release(REFS_ON_FREELIST - 1, &node->refs) == 1)
-				continue;
-		}
-		return;
-	}
-}
-
-static inline void freelist_add(struct freelist_node *node, struct freelist_head *list)
-{
-	/*
-	 * We know that the should-be-on-freelist bit is 0 at this point, so
-	 * it's safe to set it using a fetch_add.
-	 */
-	if (!atomic_fetch_add_release(REFS_ON_FREELIST, &node->refs)) {
-		/*
-		 * Oh look! We were the last ones referencing this node, and we
-		 * know we want to add it to the free list, so let's do it!
-		 */
-		__freelist_add(node, list);
-	}
-}
-
-static inline struct freelist_node *freelist_try_get(struct freelist_head *list)
-{
-	struct freelist_node *prev, *next, *head = smp_load_acquire(&list->head);
-	unsigned int refs;
-
-	while (head) {
-		prev = head;
-		refs = atomic_read(&head->refs);
-		if ((refs & REFS_MASK) == 0 ||
-		    !atomic_try_cmpxchg_acquire(&head->refs, &refs, refs+1)) {
-			head = smp_load_acquire(&list->head);
-			continue;
-		}
-
-		/*
-		 * Good, reference count has been incremented (it wasn't at
-		 * zero), which means we can read the next and not worry about
-		 * it changing between now and the time we do the CAS.
-		 */
-		next = READ_ONCE(head->next);
-		if (try_cmpxchg_acquire(&list->head, &head, next)) {
-			/*
-			 * Yay, got the node. This means it was on the list,
-			 * which means should-be-on-freelist must be false no
-			 * matter the refcount (because nobody else knows it's
-			 * been taken off yet, it can't have been put back on).
-			 */
-			WARN_ON_ONCE(atomic_read(&head->refs) & REFS_ON_FREELIST);
-
-			/*
-			 * Decrease refcount twice, once for our ref, and once
-			 * for the list's ref.
-			 */
-			atomic_fetch_add(-2, &head->refs);
-
-			return head;
-		}
-
-		/*
-		 * OK, the head must have changed on us, but we still need to decrement
-		 * the refcount we increased.
-		 */
-		refs = atomic_fetch_add(-1, &prev->refs);
-		if (refs == REFS_ON_FREELIST + 1)
-			__freelist_add(prev, list);
-	}
-
-	return NULL;
-}
-
-#endif /* FREELIST_H */
_

Patches currently in -mm which might be from wuqiang.matt@bytedance.com are

lib-objpool-added-ring-array-based-lockless-mpmc-queue.patch
lib-objpool-test-module-added.patch
kprobes-kretprobe-scalability-improvement-with-objpool.patch
kprobes-freelisth-removed.patch
kprobeslib-kretprobe-scalability-improvement.patch