mirror of
https://github.com/torvalds/linux.git
synced 2025-11-04 10:40:15 +02:00
375700bab5
The function is small enough that it should be, and it's a (very) hot path for io_uring. Doing this actually reduces my vmlinux text size for my standard build/test box. Before: axboe@r7625 ~/g/linux (test)> size vmlinux text data bss dec hex filename 19892174 5938310 2470432 28300916 1afd674 vmlinux After: axboe@r7625 ~/g/linux (test)> size vmlinux text data bss dec hex filename 19891878 5938310 2470436 28300624 1afd550 vmlinux Link: https://lkml.kernel.org/r/f1d104c6-7ac8-457a-a53d-6bb741421b2f@kernel.dk Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
94 lines
2.7 KiB
C
94 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* Lock-less NULL terminated single linked list
|
|
*
|
|
* The basic atomic operation of this list is cmpxchg on long. On
|
|
* architectures that don't have NMI-safe cmpxchg implementation, the
|
|
* list can NOT be used in NMI handlers. So code that uses the list in
|
|
* an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
|
|
*
|
|
* Copyright 2010,2011 Intel Corp.
|
|
* Author: Huang Ying <ying.huang@intel.com>
|
|
*/
|
|
#include <linux/kernel.h>
|
|
#include <linux/export.h>
|
|
#include <linux/llist.h>
|
|
|
|
/**
|
|
* llist_del_first - delete the first entry of lock-less list
|
|
* @head: the head for your lock-less list
|
|
*
|
|
* If list is empty, return NULL, otherwise, return the first entry
|
|
* deleted, this is the newest added one.
|
|
*
|
|
* Only one llist_del_first user can be used simultaneously with
|
|
* multiple llist_add users without lock. Because otherwise
|
|
* llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
|
|
* llist_add) sequence in another user may change @head->first->next,
|
|
* but keep @head->first. If multiple consumers are needed, please
|
|
* use llist_del_all or use lock between consumers.
|
|
*/
|
|
struct llist_node *llist_del_first(struct llist_head *head)
|
|
{
|
|
struct llist_node *entry, *next;
|
|
|
|
entry = smp_load_acquire(&head->first);
|
|
do {
|
|
if (entry == NULL)
|
|
return NULL;
|
|
next = READ_ONCE(entry->next);
|
|
} while (!try_cmpxchg(&head->first, &entry, next));
|
|
|
|
return entry;
|
|
}
|
|
EXPORT_SYMBOL_GPL(llist_del_first);
|
|
|
|
/**
|
|
* llist_del_first_this - delete given entry of lock-less list if it is first
|
|
* @head: the head for your lock-less list
|
|
* @this: a list entry.
|
|
*
|
|
* If head of the list is given entry, delete and return %true else
|
|
* return %false.
|
|
*
|
|
* Multiple callers can safely call this concurrently with multiple
|
|
* llist_add() callers, providing all the callers offer a different @this.
|
|
*/
|
|
bool llist_del_first_this(struct llist_head *head,
|
|
struct llist_node *this)
|
|
{
|
|
struct llist_node *entry, *next;
|
|
|
|
/* acquire ensures orderig wrt try_cmpxchg() is llist_del_first() */
|
|
entry = smp_load_acquire(&head->first);
|
|
do {
|
|
if (entry != this)
|
|
return false;
|
|
next = READ_ONCE(entry->next);
|
|
} while (!try_cmpxchg(&head->first, &entry, next));
|
|
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL_GPL(llist_del_first_this);
|
|
|
|
/**
|
|
* llist_reverse_order - reverse order of a llist chain
|
|
* @head: first item of the list to be reversed
|
|
*
|
|
* Reverse the order of a chain of llist entries and return the
|
|
* new first entry.
|
|
*/
|
|
struct llist_node *llist_reverse_order(struct llist_node *head)
|
|
{
|
|
struct llist_node *new_head = NULL;
|
|
|
|
while (head) {
|
|
struct llist_node *tmp = head;
|
|
head = head->next;
|
|
tmp->next = new_head;
|
|
new_head = tmp;
|
|
}
|
|
|
|
return new_head;
|
|
}
|
|
EXPORT_SYMBOL_GPL(llist_reverse_order);
|