| 0,0 → 1,345 |
|---|
| /* |
| * Copyright (c) 2006 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| /** @addtogroup sync |
| * @{ |
| */ |
| |
| /** |
| * @file |
| * @brief Kernel backend for futexes. |
| */ |
| |
| #include <synch/futex.h> |
| #include <synch/rwlock.h> |
| #include <synch/spinlock.h> |
| #include <synch/synch.h> |
| #include <mm/frame.h> |
| #include <mm/page.h> |
| #include <mm/slab.h> |
| #include <proc/thread.h> |
| #include <proc/task.h> |
| #include <genarch/mm/page_pt.h> |
| #include <genarch/mm/page_ht.h> |
| #include <adt/hash_table.h> |
| #include <adt/list.h> |
| #include <arch.h> |
| #include <align.h> |
| #include <panic.h> |
| #include <errno.h> |
| #include <print.h> |
| |
| #define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */ |
| |
| static void futex_initialize(futex_t *futex); |
| |
| static futex_t *futex_find(uintptr_t paddr); |
| static index_t futex_ht_hash(unative_t *key); |
| static bool futex_ht_compare(unative_t *key, count_t keys, link_t *item); |
| static void futex_ht_remove_callback(link_t *item); |
| |
| /** |
| * Read-write lock protecting global futex hash table. |
| * It is also used to serialize access to all futex_t structures. |
| * Must be acquired before the task futex B+tree lock. |
| */ |
| static rwlock_t futex_ht_lock; |
| |
| /** Futex hash table. */ |
| static hash_table_t futex_ht; |
| |
| /** Futex hash table operations. */ |
| static hash_table_operations_t futex_ht_ops = { |
| .hash = futex_ht_hash, |
| .compare = futex_ht_compare, |
| .remove_callback = futex_ht_remove_callback |
| }; |
| |
| /** Initialize futex subsystem. */ |
| void futex_init(void) |
| { |
| rwlock_initialize(&futex_ht_lock); |
| hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops); |
| } |
| |
| /** Initialize kernel futex structure. |
| * |
| * @param futex Kernel futex structure. |
| */ |
| void futex_initialize(futex_t *futex) |
| { |
| waitq_initialize(&futex->wq); |
| link_initialize(&futex->ht_link); |
| futex->paddr = 0; |
| futex->refcount = 1; |
| } |
| |
| /** Sleep in futex wait queue. |
| * |
| * @param uaddr Userspace address of the futex counter. |
| * @param usec If non-zero, number of microseconds this thread is willing to |
| * sleep. |
| * @param flags Select mode of operation. |
| * |
| * @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See |
| * synch.h. If there is no physical mapping for uaddr ENOENT is returned. |
| */ |
| unative_t sys_futex_sleep_timeout(uintptr_t uaddr, uint32_t usec, int flags) |
| { |
| futex_t *futex; |
| uintptr_t paddr; |
| pte_t *t; |
| ipl_t ipl; |
| |
| ipl = interrupts_disable(); |
| |
| /* |
| * Find physical address of futex counter. |
| */ |
| page_table_lock(AS, true); |
| t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
| page_table_unlock(AS, true); |
| interrupts_restore(ipl); |
| return (unative_t) ENOENT; |
| } |
| paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| page_table_unlock(AS, true); |
| |
| interrupts_restore(ipl); |
| |
| futex = futex_find(paddr); |
| |
| return (unative_t) waitq_sleep_timeout(&futex->wq, usec, flags | |
| SYNCH_FLAGS_INTERRUPTIBLE); |
| } |
| |
| /** Wakeup one thread waiting in futex wait queue. |
| * |
| * @param uaddr Userspace address of the futex counter. |
| * |
| * @return ENOENT if there is no physical mapping for uaddr. |
| */ |
| unative_t sys_futex_wakeup(uintptr_t uaddr) |
| { |
| futex_t *futex; |
| uintptr_t paddr; |
| pte_t *t; |
| ipl_t ipl; |
| |
| ipl = interrupts_disable(); |
| |
| /* |
| * Find physical address of futex counter. |
| */ |
| page_table_lock(AS, true); |
| t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
| page_table_unlock(AS, true); |
| interrupts_restore(ipl); |
| return (unative_t) ENOENT; |
| } |
| paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| page_table_unlock(AS, true); |
| |
| interrupts_restore(ipl); |
| |
| futex = futex_find(paddr); |
| |
| waitq_wakeup(&futex->wq, WAKEUP_FIRST); |
| |
| return 0; |
| } |
| |
| /** Find kernel address of the futex structure corresponding to paddr. |
| * |
| * If the structure does not exist already, a new one is created. |
| * |
| * @param paddr Physical address of the userspace futex counter. |
| * |
| * @return Address of the kernel futex structure. |
| */ |
| futex_t *futex_find(uintptr_t paddr) |
| { |
| link_t *item; |
| futex_t *futex; |
| btree_node_t *leaf; |
| |
| /* |
| * Find the respective futex structure |
| * or allocate new one if it does not exist already. |
| */ |
| rwlock_read_lock(&futex_ht_lock); |
| item = hash_table_find(&futex_ht, &paddr); |
| if (item) { |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| |
| /* |
| * See if the current task knows this futex. |
| */ |
| mutex_lock(&TASK->futexes_lock); |
| if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
| /* |
| * The futex is new to the current task. |
| * However, we only have read access. |
| * Gain write access and try again. |
| */ |
| mutex_unlock(&TASK->futexes_lock); |
| goto gain_write_access; |
| } |
| mutex_unlock(&TASK->futexes_lock); |
| |
| rwlock_read_unlock(&futex_ht_lock); |
| } else { |
| gain_write_access: |
| /* |
| * Upgrade to writer is not currently supported, |
| * therefore, it is necessary to release the read lock |
| * and reacquire it as a writer. |
| */ |
| rwlock_read_unlock(&futex_ht_lock); |
| |
| rwlock_write_lock(&futex_ht_lock); |
| /* |
| * Avoid possible race condition by searching |
| * the hash table once again with write access. |
| */ |
| item = hash_table_find(&futex_ht, &paddr); |
| if (item) { |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| |
| /* |
| * See if this futex is known to the current task. |
| */ |
| mutex_lock(&TASK->futexes_lock); |
| if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
| /* |
| * The futex is new to the current task. |
| * Upgrade its reference count and put it to the |
| * current task's B+tree of known futexes. |
| */ |
| futex->refcount++; |
| btree_insert(&TASK->futexes, paddr, futex, |
| leaf); |
| } |
| mutex_unlock(&TASK->futexes_lock); |
| |
| rwlock_write_unlock(&futex_ht_lock); |
| } else { |
| futex = (futex_t *) malloc(sizeof(futex_t), 0); |
| futex_initialize(futex); |
| futex->paddr = paddr; |
| hash_table_insert(&futex_ht, &paddr, &futex->ht_link); |
| |
| /* |
| * This is the first task referencing the futex. |
| * It can be directly inserted into its |
| * B+tree of known futexes. |
| */ |
| mutex_lock(&TASK->futexes_lock); |
| btree_insert(&TASK->futexes, paddr, futex, NULL); |
| mutex_unlock(&TASK->futexes_lock); |
| |
| rwlock_write_unlock(&futex_ht_lock); |
| } |
| } |
| |
| return futex; |
| } |
| |
| /** Compute hash index into futex hash table. |
| * |
| * @param key Address where the key (i.e. physical address of futex counter) is |
| * stored. |
| * |
| * @return Index into futex hash table. |
| */ |
| index_t futex_ht_hash(unative_t *key) |
| { |
| return *key & (FUTEX_HT_SIZE-1); |
| } |
| |
| /** Compare futex hash table item with a key. |
| * |
| * @param key Address where the key (i.e. physical address of futex counter) is |
| * stored. |
| * |
| * @return True if the item matches the key. False otherwise. |
| */ |
| bool futex_ht_compare(unative_t *key, count_t keys, link_t *item) |
| { |
| futex_t *futex; |
| |
| ASSERT(keys == 1); |
| |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| return *key == futex->paddr; |
| } |
| |
| /** Callback for removal items from futex hash table. |
| * |
| * @param item Item removed from the hash table. |
| */ |
| void futex_ht_remove_callback(link_t *item) |
| { |
| futex_t *futex; |
| |
| futex = hash_table_get_instance(item, futex_t, ht_link); |
| free(futex); |
| } |
| |
| /** Remove references from futexes known to the current task. */ |
| void futex_cleanup(void) |
| { |
| link_t *cur; |
| |
| rwlock_write_lock(&futex_ht_lock); |
| mutex_lock(&TASK->futexes_lock); |
| |
| for (cur = TASK->futexes.leaf_head.next; |
| cur != &TASK->futexes.leaf_head; cur = cur->next) { |
| btree_node_t *node; |
| unsigned int i; |
| |
| node = list_get_instance(cur, btree_node_t, leaf_link); |
| for (i = 0; i < node->keys; i++) { |
| futex_t *ftx; |
| uintptr_t paddr = node->key[i]; |
| |
| ftx = (futex_t *) node->value[i]; |
| if (--ftx->refcount == 0) |
| hash_table_remove(&futex_ht, &paddr, 1); |
| } |
| } |
| |
| mutex_unlock(&TASK->futexes_lock); |
| rwlock_write_unlock(&futex_ht_lock); |
| } |
| |
| /** @} |
| */ |