Index: uspace/lib/c/Makefile =================================================================== --- uspace/lib/c/Makefile (revision 3875f1064135338c90e634c95c82359a59d27007) +++ uspace/lib/c/Makefile (revision be6e37a1450dc9ae009c1198f1541fa2c80b2a0c) @@ -79,5 +79,4 @@ generic/pcb.c \ generic/smc.c \ - generic/smp_memory_barrier.c \ generic/task.c \ generic/imath.c \ @@ -134,5 +133,4 @@ generic/thread/tls.c \ generic/thread/futex.c \ - generic/thread/rcu.c \ generic/thread/mpsc.c \ generic/sysinfo.c \ Index: uspace/lib/c/generic/smp_memory_barrier.c =================================================================== --- uspace/lib/c/generic/smp_memory_barrier.c (revision 3875f1064135338c90e634c95c82359a59d27007) +++ (revision ) @@ -1,44 +1,0 @@ -/* - * Copyright (c) 2012 Adam Hraska - * 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 libc - * @{ - */ -/** @file - */ - -#include -#include - -void smp_memory_barrier(void) -{ - __SYSCALL0(SYS_SMP_MEMORY_BARRIER); -} - -/** @} - */ Index: uspace/lib/c/generic/thread/rcu.c =================================================================== --- uspace/lib/c/generic/thread/rcu.c (revision 3875f1064135338c90e634c95c82359a59d27007) +++ (revision ) @@ -1,432 +1,0 @@ -/* - * Copyright (c) 2012 Adam Hraska - * 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 libc - * @{ - */ -/** - * @file - * - * User space RCU is based on URCU utilizing signals [1]. This - * implementation does not however signal each thread of the process - * to issue a memory barrier. Instead, we introduced a syscall that - * issues memory barriers (via IPIs) on cpus that are running threads - * of the current process. First, it does not require us to schedule - * and run every thread of the process. Second, IPIs are less intrusive - * than switching contexts and entering user space. - * - * This algorithm is further modified to require a single instead of - * two reader group changes per grace period. Signal-URCU flips - * the reader group and waits for readers of the previous group - * twice in succession in order to wait for new readers that were - * delayed and mistakenly associated with the previous reader group. - * The modified algorithm ensures that the new reader group is - * always empty (by explicitly waiting for it to become empty). - * Only then does it flip the reader group and wait for preexisting - * readers of the old reader group (invariant of SRCU [2, 3]). - * - * - * [1] User-level implementations of read-copy update, - * 2012, appendix - * http://www.rdrop.com/users/paulmck/RCU/urcu-supp-accepted.2011.08.30a.pdf - * - * [2] linux/kernel/srcu.c in Linux 3.5-rc2, - * 2012 - * http://tomoyo.sourceforge.jp/cgi-bin/lxr/source/kernel/srcu.c?v=linux-3.5-rc2-ccs-1.8.3 - * - * [3] [RFC PATCH 5/5 single-thread-version] implement - * per-domain single-thread state machine, - * 2012, Lai - * https://lkml.org/lkml/2012/3/6/586 - */ - -#include "rcu.h" -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include - -#include "../private/fibril.h" - -/** RCU sleeps for RCU_SLEEP_MS before polling an active RCU reader again. */ -#define RCU_SLEEP_MS 10 - -#define RCU_NESTING_SHIFT 1 -#define RCU_NESTING_INC (1 << RCU_NESTING_SHIFT) -#define RCU_GROUP_BIT_MASK (size_t)(RCU_NESTING_INC - 1) -#define RCU_GROUP_A (size_t)(0 | RCU_NESTING_INC) -#define RCU_GROUP_B (size_t)(1 | RCU_NESTING_INC) - -/** Fibril local RCU data. */ -typedef struct fibril_rcu_data { - size_t nesting_cnt; - link_t link; - bool registered; -} fibril_rcu_data_t; - -/** Process global RCU data. */ -typedef struct rcu_data { - size_t cur_gp; - size_t reader_group; - fibril_rmutex_t list_mutex; - list_t fibrils_list; - struct { - fibril_rmutex_t mutex; - bool locked; - list_t blocked_fibrils; - } sync_lock; -} rcu_data_t; - -typedef struct blocked_fibril { - fibril_event_t unblock; - link_t link; - bool is_ready; -} blocked_fibril_t; - -/** Fibril local RCU data. */ -static fibril_local fibril_rcu_data_t fibril_rcu = { - .nesting_cnt = 0, - .link = { - .next = NULL, - .prev = NULL - }, - .registered = false -}; - -/** Process global RCU data. */ -static rcu_data_t rcu = { - .cur_gp = 0, - .reader_group = RCU_GROUP_A, - .list_mutex = FIBRIL_RMUTEX_INITIALIZER(rcu.list_mutex), - .fibrils_list = LIST_INITIALIZER(rcu.fibrils_list), - .sync_lock = { - .mutex = FIBRIL_RMUTEX_INITIALIZER(rcu.sync_lock.mutex), - .locked = false, - .blocked_fibrils = LIST_INITIALIZER(rcu.sync_lock.blocked_fibrils), - }, -}; - -static void wait_for_readers(size_t reader_group); -static void force_mb_in_all_threads(void); -static bool is_preexisting_reader(const fibril_rcu_data_t *fib, size_t group); - -static void lock_sync(void); -static void unlock_sync(void); -static void sync_sleep(void); - -static bool is_in_group(size_t nesting_cnt, size_t group); -static bool is_in_reader_section(size_t nesting_cnt); -static size_t get_other_group(size_t group); - -/** Registers a fibril so it may start using RCU read sections. - * - * A fibril must be registered with rcu before it can enter RCU critical - * sections delineated by rcu_read_lock() and rcu_read_unlock(). - */ -void rcu_register_fibril(void) -{ - assert(!fibril_rcu.registered); - - fibril_rmutex_lock(&rcu.list_mutex); - list_append(&fibril_rcu.link, &rcu.fibrils_list); - fibril_rmutex_unlock(&rcu.list_mutex); - - fibril_rcu.registered = true; -} - -/** Deregisters a fibril that had been using RCU read sections. - * - * A fibril must be deregistered before it exits if it had - * been registered with rcu via rcu_register_fibril(). - */ -void rcu_deregister_fibril(void) -{ - assert(fibril_rcu.registered); - - /* - * Forcefully unlock any reader sections. The fibril is exiting - * so it is not holding any references to data protected by the - * rcu section. Therefore, it is safe to unlock. Otherwise, - * rcu_synchronize() would wait indefinitely. - */ - memory_barrier(); - fibril_rcu.nesting_cnt = 0; - - fibril_rmutex_lock(&rcu.list_mutex); - list_remove(&fibril_rcu.link); - fibril_rmutex_unlock(&rcu.list_mutex); - - fibril_rcu.registered = false; -} - -/** Delimits the start of an RCU reader critical section. - * - * RCU reader sections may be nested. - */ -void rcu_read_lock(void) -{ - assert(fibril_rcu.registered); - - size_t nesting_cnt = ACCESS_ONCE(fibril_rcu.nesting_cnt); - - if (0 == (nesting_cnt >> RCU_NESTING_SHIFT)) { - ACCESS_ONCE(fibril_rcu.nesting_cnt) = ACCESS_ONCE(rcu.reader_group); - /* Required by MB_FORCE_L */ - compiler_barrier(); /* CC_BAR_L */ - } else { - ACCESS_ONCE(fibril_rcu.nesting_cnt) = nesting_cnt + RCU_NESTING_INC; - } -} - -/** Delimits the end of an RCU reader critical section. */ -void rcu_read_unlock(void) -{ - assert(fibril_rcu.registered); - assert(rcu_read_locked()); - - /* Required by MB_FORCE_U */ - compiler_barrier(); /* CC_BAR_U */ - /* todo: ACCESS_ONCE(nesting_cnt) ? */ - fibril_rcu.nesting_cnt -= RCU_NESTING_INC; -} - -/** Returns true if the current fibril is in an RCU reader section. */ -bool rcu_read_locked(void) -{ - return 0 != (fibril_rcu.nesting_cnt >> RCU_NESTING_SHIFT); -} - -/** Blocks until all preexisting readers exit their critical sections. */ -void rcu_synchronize(void) -{ - assert(!rcu_read_locked()); - - /* Contain load of rcu.cur_gp. */ - memory_barrier(); - - /* Approximately the number of the GP in progress. */ - size_t gp_in_progress = ACCESS_ONCE(rcu.cur_gp); - - lock_sync(); - - /* - * Exit early if we were stuck waiting for the mutex for a full grace - * period. Started waiting during gp_in_progress (or gp_in_progress + 1 - * if the value propagated to this cpu too late) so wait for the next - * full GP, gp_in_progress + 1, to finish. Ie don't wait if the GP - * after that, gp_in_progress + 2, already started. - */ - /* rcu.cur_gp >= gp_in_progress + 2, but tolerates overflows. */ - if (rcu.cur_gp != gp_in_progress && rcu.cur_gp + 1 != gp_in_progress) { - unlock_sync(); - return; - } - - ++ACCESS_ONCE(rcu.cur_gp); - - /* - * Pairs up with MB_FORCE_L (ie CC_BAR_L). Makes changes prior - * to rcu_synchronize() visible to new readers. - */ - memory_barrier(); /* MB_A */ - - /* - * Pairs up with MB_A. - * - * If the memory barrier is issued before CC_BAR_L in the target - * thread, it pairs up with MB_A and the thread sees all changes - * prior to rcu_synchronize(). Ie any reader sections are new - * rcu readers. - * - * If the memory barrier is issued after CC_BAR_L, it pairs up - * with MB_B and it will make the most recent nesting_cnt visible - * in this thread. Since the reader may have already accessed - * memory protected by RCU (it ran instructions passed CC_BAR_L), - * it is a preexisting reader. Seeing the most recent nesting_cnt - * ensures the thread will be identified as a preexisting reader - * and we will wait for it in wait_for_readers(old_reader_group). - */ - force_mb_in_all_threads(); /* MB_FORCE_L */ - - /* - * Pairs with MB_FORCE_L (ie CC_BAR_L, CC_BAR_U) and makes the most - * current fibril.nesting_cnt visible to this cpu. - */ - read_barrier(); /* MB_B */ - - size_t new_reader_group = get_other_group(rcu.reader_group); - wait_for_readers(new_reader_group); - - /* Separates waiting for readers in new_reader_group from group flip. */ - memory_barrier(); - - /* Flip the group new readers should associate with. */ - size_t old_reader_group = rcu.reader_group; - rcu.reader_group = new_reader_group; - - /* Flip the group before waiting for preexisting readers in the old group.*/ - memory_barrier(); - - wait_for_readers(old_reader_group); - - /* MB_FORCE_U */ - force_mb_in_all_threads(); /* MB_FORCE_U */ - - unlock_sync(); -} - -/** Issues a memory barrier in each thread of this process. */ -static void force_mb_in_all_threads(void) -{ - /* - * Only issue barriers in running threads. The scheduler will - * execute additional memory barriers when switching to threads - * of the process that are currently not running. - */ - smp_memory_barrier(); -} - -/** Waits for readers of reader_group to exit their readers sections. */ -static void wait_for_readers(size_t reader_group) -{ - fibril_rmutex_lock(&rcu.list_mutex); - - list_t quiescent_fibrils; - list_initialize(&quiescent_fibrils); - - while (!list_empty(&rcu.fibrils_list)) { - list_foreach_safe(rcu.fibrils_list, fibril_it, next_fibril) { - fibril_rcu_data_t *fib = member_to_inst(fibril_it, - fibril_rcu_data_t, link); - - if (is_preexisting_reader(fib, reader_group)) { - fibril_rmutex_unlock(&rcu.list_mutex); - sync_sleep(); - fibril_rmutex_lock(&rcu.list_mutex); - /* Break to while loop. */ - break; - } else { - list_remove(fibril_it); - list_append(fibril_it, &quiescent_fibrils); - } - } - } - - list_concat(&rcu.fibrils_list, &quiescent_fibrils); - fibril_rmutex_unlock(&rcu.list_mutex); -} - -static void lock_sync(void) -{ - fibril_rmutex_lock(&rcu.sync_lock.mutex); - if (rcu.sync_lock.locked) { - blocked_fibril_t blocked_fib; - blocked_fib.unblock = FIBRIL_EVENT_INIT; - - list_append(&blocked_fib.link, &rcu.sync_lock.blocked_fibrils); - - do { - blocked_fib.is_ready = false; - fibril_rmutex_unlock(&rcu.sync_lock.mutex); - fibril_wait_for(&blocked_fib.unblock); - fibril_rmutex_lock(&rcu.sync_lock.mutex); - } while (rcu.sync_lock.locked); - - list_remove(&blocked_fib.link); - rcu.sync_lock.locked = true; - } else { - rcu.sync_lock.locked = true; - } -} - -static void unlock_sync(void) -{ - assert(rcu.sync_lock.locked); - - /* Unlock but wake up any fibrils waiting for the lock. */ - - if (!list_empty(&rcu.sync_lock.blocked_fibrils)) { - blocked_fibril_t *blocked_fib = member_to_inst( - list_first(&rcu.sync_lock.blocked_fibrils), blocked_fibril_t, link); - - if (!blocked_fib->is_ready) { - blocked_fib->is_ready = true; - fibril_notify(&blocked_fib->unblock); - } - } - - rcu.sync_lock.locked = false; - fibril_rmutex_unlock(&rcu.sync_lock.mutex); -} - -static void sync_sleep(void) -{ - assert(rcu.sync_lock.locked); - /* - * Release the futex to avoid deadlocks in singlethreaded apps - * but keep sync locked. - */ - fibril_rmutex_unlock(&rcu.sync_lock.mutex); - fibril_usleep(RCU_SLEEP_MS * 1000); - fibril_rmutex_lock(&rcu.sync_lock.mutex); -} - -static bool is_preexisting_reader(const fibril_rcu_data_t *fib, size_t group) -{ - size_t nesting_cnt = ACCESS_ONCE(fib->nesting_cnt); - - return is_in_group(nesting_cnt, group) && is_in_reader_section(nesting_cnt); -} - -static size_t get_other_group(size_t group) -{ - if (group == RCU_GROUP_A) - return RCU_GROUP_B; - else - return RCU_GROUP_A; -} - -static bool is_in_reader_section(size_t nesting_cnt) -{ - return RCU_NESTING_INC <= nesting_cnt; -} - -static bool is_in_group(size_t nesting_cnt, size_t group) -{ - return (nesting_cnt & RCU_GROUP_BIT_MASK) == (group & RCU_GROUP_BIT_MASK); -} - -/** @} - */ Index: uspace/lib/c/include/barrier.h =================================================================== --- uspace/lib/c/include/barrier.h (revision 3875f1064135338c90e634c95c82359a59d27007) +++ uspace/lib/c/include/barrier.h (revision be6e37a1450dc9ae009c1198f1541fa2c80b2a0c) @@ -38,6 +38,4 @@ #include -extern void smp_memory_barrier(void); - static inline void compiler_barrier(void) { Index: uspace/lib/c/include/rcu.h =================================================================== --- uspace/lib/c/include/rcu.h (revision 3875f1064135338c90e634c95c82359a59d27007) +++ (revision ) @@ -1,106 +1,0 @@ -/* - * Copyright (c) 2012 Adam Hraska - * 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 libc - * @{ - */ -/** - * @file - */ - -#ifndef LIBURCU_RCU_H_ -#define LIBURCU_RCU_H_ - -#include -#include - -/** Use to assign a pointer to newly initialized data to a rcu reader - * accessible pointer. - * - * Example: - * @code - * typedef struct exam { - * struct exam *next; - * int grade; - * } exam_t; - * - * exam_t *exam_list; - * // .. - * - * // Insert at the beginning of the list. - * exam_t *my_exam = malloc(sizeof(exam_t)); - * my_exam->grade = 5; - * my_exam->next = exam_list; - * rcu_assign(exam_list, my_exam); - * - * // Changes properly propagate. Every reader either sees - * // the old version of exam_list or the new version with - * // the fully initialized my_exam. - * rcu_synchronize(); - * // Now we can be sure every reader sees my_exam. - * - * @endcode - */ -#define rcu_assign(ptr, value) \ - do { \ - memory_barrier(); \ - (ptr) = (value); \ - } while (0) - -/** Use to access RCU protected data in a reader section. - * - * Example: - * @code - * exam_t *exam_list; - * // ... - * - * rcu_read_lock(); - * exam_t *first_exam = rcu_access(exam_list); - * // We can now safely use first_exam, it won't change - * // under us while we're using it. - * - * // .. - * rcu_read_unlock(); - * @endcode - */ -#define rcu_access(ptr) ACCESS_ONCE(ptr) - -extern void rcu_register_fibril(void); -extern void rcu_deregister_fibril(void); - -extern void rcu_read_lock(void); -extern void rcu_read_unlock(void); - -extern bool rcu_read_locked(void); - -extern void rcu_synchronize(void); - -#endif - -/** @} - */