| 0,0 → 1,235 |
|---|
| /* |
| * 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. |
| */ |
| |
| /** |
| * Kernel backend for futexes. |
| * Deallocation of orphaned kernel-side futex structures is not currently implemented. |
| * Timeouting futexes are currently not implemented. |
| */ |
| |
| #include <synch/futex.h> |
| #include <synch/rwlock.h> |
| #include <synch/synch.h> |
| #include <mm/frame.h> |
| #include <mm/page.h> |
| #include <mm/slab.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 index_t futex_ht_hash(__native *key); |
| static bool futex_ht_compare(__native *key, count_t keys, link_t *item); |
| static void futex_ht_remove_callback(link_t *item); |
| |
| /** Read-write lock protecting global futex hash table. */ |
| 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; |
| } |
| |
| /** Sleep in futex wait queue. |
| * |
| * @param uaddr Userspace address of the futex counter. |
| * |
| * @return One of ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h. |
| * If there is no physical mapping for uaddr ENOENT is returned. |
| */ |
| __native sys_futex_sleep(__address uaddr) |
| { |
| futex_t *futex; |
| __address paddr; |
| link_t *item; |
| pte_t *t; |
| |
| /* |
| * 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); |
| return (__native) ENOENT; |
| } |
| paddr = PFN2ADDR(PTE_GET_FRAME(t)) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| page_table_unlock(AS, true); |
| |
| /* |
| * 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); |
| rwlock_read_unlock(&futex_ht_lock); |
| } else { |
| /* |
| * 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); |
| /* |
| * Detect 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); |
| 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); |
| rwlock_write_unlock(&futex_ht_lock); |
| } |
| } |
| |
| return (__native) waitq_sleep(&futex->wq); |
| } |
| |
| /** Wakeup one thread waiting in futex wait queue. |
| * |
| * @param uaddr Userspace address of the futex counter. |
| * |
| * @return ENOENT if there is no futex associated with the address |
| * or if there is no physical mapping for uaddr. |
| */ |
| __native sys_futex_wakeup(__address uaddr) |
| { |
| futex_t *futex = NULL; |
| __address paddr; |
| link_t *item; |
| pte_t *t; |
| |
| /* |
| * 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); |
| return (__native) ENOENT; |
| } |
| paddr = PFN2ADDR(PTE_GET_FRAME(t)) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE)); |
| page_table_unlock(AS, true); |
| |
| /* |
| * Find the respective futex structure. |
| */ |
| 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); |
| } |
| rwlock_read_unlock(&futex_ht_lock); |
| |
| if (!futex) |
| return (__native) ENOENT; |
| |
| waitq_wakeup(&futex->wq, WAKEUP_FIRST); |
| |
| return 0; |
| } |
| |
| /** 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(__native *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(__native *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); |
| } |