From 9cc63f8bcd560c760d0b12e15bba8f81c86237cf Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 14 Aug 2026 15:43:51 -0700 Subject: Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEAD Changes: Make expedited grace periods expedite normal RCU callbacks Miscellaneous fixes: * Improve diagnostic output with character task states. * Mark accesses to inform KCSAN of concurrency design. * Move from kmalloc() to kmalloc_obj(). * Documentation updates. * Improve handling of RCU deferred quiescent states. * Clean up unused function arguments and structure fields. * Reduce show_rcu_gp_kthreads() stack space. Tasks RCU updates: * Clean up after SRCU re-implementation of Tasks Trace RCU. * Mark accesses to inform KCSAN of concurrency design. * Add ->lazy_timer status to diagnostic output. * Remove an unnecessary memory barrier. * Fix a data race, courtesy of KCSAN. * Documentation updates. * Convert cond_resched_tasks_rcu_qs() from macro to static inline function. SRCU updates: * Add Rust helpers for SRCU. * Avoid losing queued work at cleanup_srcu_struct() time. Torture-test updates: * Preparation work for immediate RCU priority deboosting. * Test RCU readers from real interrupt handlers (as opposed to softirq). * Simplify code through use of cpumask_next_wrap(). * Improve diagnostic output with character task states. * Add rcutorture.nwriters parameter to allow lightweight stall testing, and rcutorture.stall_only to make doing so easier. * Test an RCU Tasks Trace grace period implying an RCU grace period. * Make RCU Tasks Trace torturing track reader batches. * Fix a data race, courtesy of KCSAN. * Plug a shuffle_tmp_mask memory leak on kthread spawn failure. --- lib/plist.c | 311 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 311 insertions(+) create mode 100644 lib/plist.c (limited to 'lib/plist.c') diff --git a/lib/plist.c b/lib/plist.c new file mode 100644 index 000000000..a5bef38ad --- /dev/null +++ b/lib/plist.c @@ -0,0 +1,311 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * lib/plist.c + * + * Descending-priority-sorted double-linked list + * + * (C) 2002-2003 Intel Corp + * Inaky Perez-Gonzalez . + * + * 2001-2005 (c) MontaVista Software, Inc. + * Daniel Walker + * + * (C) 2005 Linutronix GmbH, Thomas Gleixner + * + * Simplifications of the original code by + * Oleg Nesterov + * + * Based on simple lists (include/linux/list.h). + * + * This file contains the add / del functions which are considered to + * be too large to inline. See include/linux/plist.h for further + * information. + */ + +#include +#include + +#ifdef CONFIG_DEBUG_PLIST + +static struct plist_head test_head; + +static void plist_check_prev_next(struct list_head *t, struct list_head *p, + struct list_head *n) +{ + WARN(n->prev != p || p->next != n, + "top: %p, n: %p, p: %p\n" + "prev: %p, n: %p, p: %p\n" + "next: %p, n: %p, p: %p\n", + t, t->next, t->prev, + p, p->next, p->prev, + n, n->next, n->prev); +} + +static void plist_check_list(struct list_head *top) +{ + struct list_head *prev = top, *next = top->next; + + plist_check_prev_next(top, prev, next); + while (next != top) { + prev = next; + next = prev->next; + plist_check_prev_next(top, prev, next); + } +} + +static void plist_check_head(struct plist_head *head) +{ + if (!plist_head_empty(head)) + plist_check_list(&plist_first(head)->prio_list); + plist_check_list(&head->node_list); +} + +#else +# define plist_check_head(h) do { } while (0) +#endif + +/** + * plist_add - add @node to @head + * + * @node: &struct plist_node pointer + * @head: &struct plist_head pointer + */ +void plist_add(struct plist_node *node, struct plist_head *head) +{ + struct plist_node *first, *iter, *prev = NULL, *last, *reverse_iter; + struct list_head *node_next = &head->node_list; + + plist_check_head(head); + WARN_ON(!plist_node_empty(node)); + WARN_ON(!list_empty(&node->prio_list)); + + if (plist_head_empty(head)) + goto ins_node; + + first = iter = plist_first(head); + last = reverse_iter = list_entry(first->prio_list.prev, struct plist_node, prio_list); + + do { + if (node->prio < iter->prio) { + node_next = &iter->node_list; + break; + } else if (node->prio >= reverse_iter->prio) { + prev = reverse_iter; + iter = list_entry(reverse_iter->prio_list.next, + struct plist_node, prio_list); + if (likely(reverse_iter != last)) + node_next = &iter->node_list; + break; + } + + prev = iter; + iter = list_entry(iter->prio_list.next, + struct plist_node, prio_list); + reverse_iter = list_entry(reverse_iter->prio_list.prev, + struct plist_node, prio_list); + } while (iter != first); + + if (!prev || prev->prio != node->prio) + list_add_tail(&node->prio_list, &iter->prio_list); +ins_node: + list_add_tail(&node->node_list, node_next); + + plist_check_head(head); +} + +/** + * plist_del - Remove a @node from plist. + * + * @node: &struct plist_node pointer - entry to be removed + * @head: &struct plist_head pointer - list head + */ +void plist_del(struct plist_node *node, struct plist_head *head) +{ + plist_check_head(head); + + if (!list_empty(&node->prio_list)) { + if (node->node_list.next != &head->node_list) { + struct plist_node *next; + + next = list_entry(node->node_list.next, + struct plist_node, node_list); + + /* add the next plist_node into prio_list */ + if (list_empty(&next->prio_list)) + list_add(&next->prio_list, &node->prio_list); + } + list_del_init(&node->prio_list); + } + + list_del_init(&node->node_list); + + plist_check_head(head); +} + +/** + * plist_requeue - Requeue @node at end of same-prio entries. + * + * This is essentially an optimized plist_del() followed by + * plist_add(). It moves an entry already in the plist to + * after any other same-priority entries. + * + * @node: &struct plist_node pointer - entry to be moved + * @head: &struct plist_head pointer - list head + */ +void plist_requeue(struct plist_node *node, struct plist_head *head) +{ + struct plist_node *iter; + struct list_head *node_next = &head->node_list; + + plist_check_head(head); + BUG_ON(plist_head_empty(head)); + BUG_ON(plist_node_empty(node)); + + if (node == plist_last(head)) + return; + + iter = plist_next(node); + + if (node->prio != iter->prio) + return; + + plist_del(node, head); + + /* + * After plist_del(), iter is the replacement of the node. If the node + * was on prio_list, take shortcut to find node_next instead of looping. + */ + if (!list_empty(&iter->prio_list)) { + iter = list_entry(iter->prio_list.next, struct plist_node, + prio_list); + node_next = &iter->node_list; + goto queue; + } + + plist_for_each_continue(iter, head) { + if (node->prio != iter->prio) { + node_next = &iter->node_list; + break; + } + } +queue: + list_add_tail(&node->node_list, node_next); + + plist_check_head(head); +} + +#ifdef CONFIG_DEBUG_PLIST +#include +#include +#include +#include + +static struct plist_node __initdata test_node[241]; + +static void __init plist_test_check(int nr_expect) +{ + struct plist_node *first, *prio_pos, *node_pos; + + if (plist_head_empty(&test_head)) { + BUG_ON(nr_expect != 0); + return; + } + + prio_pos = first = plist_first(&test_head); + plist_for_each(node_pos, &test_head) { + if (nr_expect-- < 0) + break; + if (node_pos == first) + continue; + if (node_pos->prio == prio_pos->prio) { + BUG_ON(!list_empty(&node_pos->prio_list)); + continue; + } + + BUG_ON(prio_pos->prio > node_pos->prio); + BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list); + prio_pos = node_pos; + } + + BUG_ON(nr_expect != 0); + BUG_ON(prio_pos->prio_list.next != &first->prio_list); +} + +static void __init plist_test_requeue(struct plist_node *node) +{ + plist_requeue(node, &test_head); + + if (node != plist_last(&test_head)) + BUG_ON(node->prio == plist_next(node)->prio); +} + +static int __init plist_test(void) +{ + int nr_expect = 0, i, loop; + unsigned int r = local_clock(); + + printk(KERN_DEBUG "start plist test\n"); + plist_head_init(&test_head); + for (i = 0; i < ARRAY_SIZE(test_node); i++) + plist_node_init(test_node + i, 0); + + for (loop = 0; loop < 1000; loop++) { + r = r * 193939 % 47629; + i = r % ARRAY_SIZE(test_node); + if (plist_node_empty(test_node + i)) { + r = r * 193939 % 47629; + test_node[i].prio = r % 99; + plist_add(test_node + i, &test_head); + nr_expect++; + } else { + plist_del(test_node + i, &test_head); + nr_expect--; + } + plist_test_check(nr_expect); + if (!plist_node_empty(test_node + i)) { + plist_test_requeue(test_node + i); + plist_test_check(nr_expect); + } + } + + for (i = 0; i < ARRAY_SIZE(test_node); i++) { + if (plist_node_empty(test_node + i)) + continue; + plist_del(test_node + i, &test_head); + nr_expect--; + plist_test_check(nr_expect); + } + + printk(KERN_DEBUG "end plist test\n"); + + /* Worst case test for plist_add() */ + unsigned int test_data[241]; + + for (i = 0; i < ARRAY_SIZE(test_data); i++) + test_data[i] = i; + + ktime_t start, end, time_elapsed = 0; + + plist_head_init(&test_head); + + for (i = 0; i < ARRAY_SIZE(test_node); i++) { + plist_node_init(test_node + i, 0); + test_node[i].prio = test_data[i]; + } + + for (i = 0; i < ARRAY_SIZE(test_node); i++) { + if (plist_node_empty(test_node + i)) { + start = ktime_get(); + plist_add(test_node + i, &test_head); + end = ktime_get(); + time_elapsed += (end - start); + } + } + + pr_debug("plist_add worst case test time elapsed %lld\n", time_elapsed); + return 0; +} + +module_init(plist_test); + +#endif -- cgit v1.3.1