From: Mathieu Desnoyers Date: Thu, 1 Oct 2009 20:31:23 +0000 (-0400) Subject: urcu-bp: New "bulletproof" RCU library flavor X-Git-Tag: v0.2.1~2 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=fdee2e6dc73cc504ba24be89da539c68742e508e;p=userspace-rcu.git urcu-bp: New "bulletproof" RCU library flavor Slower read-side/write-side, but do not require neither of: urcu_init() rcu_register_thread() rcu_unregister_thread() It is signal safe. Specialized for the UST LTTng tracer port. Signed-off-by: Mathieu Desnoyers --- diff --git a/Makefile.inc b/Makefile.inc index 1df9d53..a27f0c3 100644 --- a/Makefile.inc +++ b/Makefile.inc @@ -6,6 +6,7 @@ DIRS=tests all: checkarch liburcu.so urcu.o \ liburcu-qsbr.so urcu-qsbr.o \ liburcu-mb.so urcu-mb.o \ + liburcu-bp.so urcu-bp.o \ liburcu-defer.so urcu-defer.o \ urcu-yield.o \ subdirs @@ -35,6 +36,9 @@ urcu.o: urcu.c urcu.h urcu-mb.o: urcu.c urcu.h $(CC) -fPIC -DURCU_MB ${CFLAGS} -c -o $@ $(SRC_DEP) +urcu-bp.o: urcu-bp.c urcu-bp.h + $(CC) -fPIC ${CFLAGS} -c -o $@ $(SRC_DEP) + urcu-qsbr.o: urcu-qsbr.c urcu-qsbr.h $(CC) -fPIC ${CFLAGS} -c -o $@ $(SRC_DEP) @@ -50,6 +54,9 @@ liburcu-qsbr.so: urcu-qsbr.o urcu-pointer.o liburcu-mb.so: urcu-mb.o urcu-pointer.o $(CC) ${LDFLAGS} -fPIC -shared -o $@ $< +liburcu-bp.so: urcu-bp.o urcu-pointer.o + $(CC) ${LDFLAGS} -fPIC -shared -o $@ $< + liburcu-defer.so: urcu-defer.o $(CC) ${LDFLAGS} -fPIC -shared -o $@ $< @@ -63,6 +70,7 @@ subdirs: install: liburcu.so cp -f liburcu.so liburcu-mb.so liburcu-qsbr.so liburcu-defer.so \ + liburcu-bp.so \ /usr/lib/ mkdir -p /usr/include/urcu cp -f urcu/arch.h urcu/arch_uatomic.h urcu/compiler.h \ @@ -70,6 +78,7 @@ install: liburcu.so /usr/include/urcu/ cp -f urcu.h urcu-static.h \ urcu-qsbr.h urcu-qsbr-static.h \ + urcu-bp.h urcu-bp-static.h \ urcu-defer.h urcu-defer-static.h \ urcu-pointer.h urcu-pointer-static.h \ /usr/include/ diff --git a/README b/README index e5c04b1..0549f24 100644 --- a/README +++ b/README @@ -50,6 +50,17 @@ Usage of liburcu-qsbr the threads are not active. It provides the fastest read-side at the expense of more intrusiveness in the application code. +Usage of liburcu-bp + + * #include + * Link with "-lurcu-bp". + * The BP library flavor stands for "bulletproof". It is specifically + designed to help tracing library to hook on applications without + requiring to modify these applications. urcu_init(), + rcu_register_thread() and rcu_unregister_thread() all become nops. + The state is dealt with by the library internally at the expense of + read-side and write-side performance. + Initialization Each thread that has reader critical sections (that uses diff --git a/tests/Makefile.inc b/tests/Makefile.inc index 92d619e..9fa9bfb 100644 --- a/tests/Makefile.inc +++ b/tests/Makefile.inc @@ -14,6 +14,7 @@ CFLAGS+=-I${LIBDIR} URCU_SIGNAL=${LIBDIR}/urcu.o ${LIBDIR}/urcu-pointer.o ${LIBDIR}/urcu.h URCU_SIGNAL_YIELD=${LIBDIR}/urcu-yield.o ${LIBDIR}/urcu-pointer.o ${LIBDIR}/urcu.h URCU_MB=${LIBDIR}/urcu-mb.o ${LIBDIR}/urcu-pointer.o ${LIBDIR}/urcu.h +URCU_BP=${LIBDIR}/urcu-bp.o ${LIBDIR}/urcu-pointer.o ${LIBDIR}/urcu.h URCU_QSBR=${LIBDIR}/urcu-qsbr.o ${LIBDIR}/urcu-pointer.o ${LIBDIR}/urcu-qsbr.h URCU_MB_DEFER=${LIBDIR}/urcu-mb.o ${LIBDIR}/urcu-defer.o ${LIBDIR}/urcu-pointer.o ${LIBDIR}/urcu.h @@ -24,7 +25,8 @@ all: test_urcu test_urcu_dynamic_link test_urcu_timing \ urcutorture-yield test_mutex test_looplen test_urcu_gc \ test_urcu_gc_mb test_qsbr_gc test_qsbr_lgc test_urcu_lgc \ test_urcu_lgc_mb test_qsbr_dynamic_link test_urcu_mb_defer \ - test_uatomic test_urcu_assign test_urcu_assign_dynamic_link + test_uatomic test_urcu_assign test_urcu_assign_dynamic_link \ + test_urcu_bp test_urcu_bp_dynamic_link api.h: ${APIHEADER} cp -f ${APIHEADER} api.h @@ -88,6 +90,13 @@ test_urcu_dynamic_link: test_urcu.c ${URCU_SIGNAL} $(CC) ${CFLAGS} -DDYNAMIC_LINK_TEST $(LDFLAGS) -o $@ $(SRC_DEP) +test_urcu_bp: test_urcu_bp.c ${URCU_BP} + $(CC) ${CFLAGS} $(LDFLAGS) -o $@ $(SRC_DEP) + +test_urcu_bp_dynamic_link: test_urcu_bp.c ${URCU_BP} + $(CC) -DDYNAMIC_LINK_TEST ${CFLAGS} $(LDFLAGS) -o $@ $(SRC_DEP) + + test_urcu_yield: test_urcu.c ${URCU_SIGNAL_YIELD} $(CC) -DDEBUG_YIELD ${CFLAGS} $(LDFLAGS) -o $@ $(SRC_DEP) diff --git a/tests/test_urcu_bp.c b/tests/test_urcu_bp.c new file mode 100644 index 0000000..8987332 --- /dev/null +++ b/tests/test_urcu_bp.c @@ -0,0 +1,427 @@ +/* + * test_urcu.c + * + * Userspace RCU library - test program + * + * Copyright February 2009 - Mathieu Desnoyers + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +/* hardcoded number of CPUs */ +#define NR_CPUS 16384 + +#if defined(_syscall0) +_syscall0(pid_t, gettid) +#elif defined(__NR_gettid) +static inline pid_t gettid(void) +{ + return syscall(__NR_gettid); +} +#else +#warning "use pid as tid" +static inline pid_t gettid(void) +{ + return getpid(); +} +#endif + +#ifndef DYNAMIC_LINK_TEST +#define _LGPL_SOURCE +#else +#define debug_yield_read() +#endif +#include + +struct test_array { + int a; +}; + +static volatile int test_go, test_stop; + +static unsigned long wdelay; + +static struct test_array *test_rcu_pointer; + +static unsigned long duration; + +/* read-side C.S. duration, in loops */ +static unsigned long rduration; + +static inline void loop_sleep(unsigned long l) +{ + while(l-- != 0) + cpu_relax(); +} + +static int verbose_mode; + +#define printf_verbose(fmt, args...) \ + do { \ + if (verbose_mode) \ + printf(fmt, args); \ + } while (0) + +static unsigned int cpu_affinities[NR_CPUS]; +static unsigned int next_aff = 0; +static int use_affinity = 0; + +pthread_mutex_t affinity_mutex = PTHREAD_MUTEX_INITIALIZER; + +static void set_affinity(void) +{ + cpu_set_t mask; + int cpu; + int ret; + + if (!use_affinity) + return; + + ret = pthread_mutex_lock(&affinity_mutex); + if (ret) { + perror("Error in pthread mutex lock"); + exit(-1); + } + cpu = cpu_affinities[next_aff++]; + ret = pthread_mutex_unlock(&affinity_mutex); + if (ret) { + perror("Error in pthread mutex unlock"); + exit(-1); + } + CPU_ZERO(&mask); + CPU_SET(cpu, &mask); + sched_setaffinity(0, sizeof(mask), &mask); +} + +/* + * returns 0 if test should end. + */ +static int test_duration_write(void) +{ + return !test_stop; +} + +static int test_duration_read(void) +{ + return !test_stop; +} + +static unsigned long long __thread nr_writes; +static unsigned long long __thread nr_reads; + +static unsigned int nr_readers; +static unsigned int nr_writers; + +pthread_mutex_t rcu_copy_mutex = PTHREAD_MUTEX_INITIALIZER; + +void rcu_copy_mutex_lock(void) +{ + int ret; + ret = pthread_mutex_lock(&rcu_copy_mutex); + if (ret) { + perror("Error in pthread mutex lock"); + exit(-1); + } +} + +void rcu_copy_mutex_unlock(void) +{ + int ret; + + ret = pthread_mutex_unlock(&rcu_copy_mutex); + if (ret) { + perror("Error in pthread mutex unlock"); + exit(-1); + } +} + +/* + * malloc/free are reusing memory areas too quickly, which does not let us + * test races appropriately. Use a large circular array for allocations. + * ARRAY_SIZE is larger than nr_writers, which insures we never run over our tail. + */ +#define ARRAY_SIZE (1048576 * nr_writers) +#define ARRAY_POISON 0xDEADBEEF +static int array_index; +static struct test_array *test_array; + +static struct test_array *test_array_alloc(void) +{ + struct test_array *ret; + int index; + + rcu_copy_mutex_lock(); + index = array_index % ARRAY_SIZE; + assert(test_array[index].a == ARRAY_POISON || + test_array[index].a == 0); + ret = &test_array[index]; + array_index++; + if (array_index == ARRAY_SIZE) + array_index = 0; + rcu_copy_mutex_unlock(); + return ret; +} + +static void test_array_free(struct test_array *ptr) +{ + if (!ptr) + return; + rcu_copy_mutex_lock(); + ptr->a = ARRAY_POISON; + rcu_copy_mutex_unlock(); +} + +void *thr_reader(void *_count) +{ + unsigned long long *count = _count; + struct test_array *local_ptr; + + printf_verbose("thread_begin %s, thread id : %lx, tid %lu\n", + "reader", pthread_self(), (unsigned long)gettid()); + + set_affinity(); + + rcu_register_thread(); + + while (!test_go) + { + } + smp_mb(); + + for (;;) { + rcu_read_lock(); + local_ptr = rcu_dereference(test_rcu_pointer); + debug_yield_read(); + if (local_ptr) + assert(local_ptr->a == 8); + if (unlikely(rduration)) + loop_sleep(rduration); + rcu_read_unlock(); + nr_reads++; + if (unlikely(!test_duration_read())) + break; + } + + rcu_unregister_thread(); + + *count = nr_reads; + printf_verbose("thread_end %s, thread id : %lx, tid %lu\n", + "reader", pthread_self(), (unsigned long)gettid()); + return ((void*)1); + +} + +void *thr_writer(void *_count) +{ + unsigned long long *count = _count; + struct test_array *new, *old; + + printf_verbose("thread_begin %s, thread id : %lx, tid %lu\n", + "writer", pthread_self(), (unsigned long)gettid()); + + set_affinity(); + + while (!test_go) + { + } + smp_mb(); + + for (;;) { + new = test_array_alloc(); + new->a = 8; + old = rcu_publish_content(&test_rcu_pointer, new); + if (old) + old->a = 0; + test_array_free(old); + nr_writes++; + if (unlikely(!test_duration_write())) + break; + if (unlikely(wdelay)) + loop_sleep(wdelay); + } + + printf_verbose("thread_end %s, thread id : %lx, tid %lu\n", + "writer", pthread_self(), (unsigned long)gettid()); + *count = nr_writes; + return ((void*)2); +} + +void show_usage(int argc, char **argv) +{ + printf("Usage : %s nr_readers nr_writers duration (s)", argv[0]); +#ifdef DEBUG_YIELD + printf(" [-r] [-w] (yield reader and/or writer)"); +#endif + printf(" [-d delay] (writer period (us))"); + printf(" [-c duration] (reader C.S. duration (in loops))"); + printf(" [-v] (verbose output)"); + printf(" [-a cpu#] [-a cpu#]... (affinity)"); + printf("\n"); +} + +int main(int argc, char **argv) +{ + int err; + pthread_t *tid_reader, *tid_writer; + void *tret; + unsigned long long *count_reader, *count_writer; + unsigned long long tot_reads = 0, tot_writes = 0; + int i, a; + + if (argc < 4) { + show_usage(argc, argv); + return -1; + } + + err = sscanf(argv[1], "%u", &nr_readers); + if (err != 1) { + show_usage(argc, argv); + return -1; + } + + err = sscanf(argv[2], "%u", &nr_writers); + if (err != 1) { + show_usage(argc, argv); + return -1; + } + + err = sscanf(argv[3], "%lu", &duration); + if (err != 1) { + show_usage(argc, argv); + return -1; + } + + for (i = 4; i < argc; i++) { + if (argv[i][0] != '-') + continue; + switch (argv[i][1]) { +#ifdef DEBUG_YIELD + case 'r': + yield_active |= YIELD_READ; + break; + case 'w': + yield_active |= YIELD_WRITE; + break; +#endif + case 'a': + if (argc < i + 2) { + show_usage(argc, argv); + return -1; + } + a = atoi(argv[++i]); + cpu_affinities[next_aff++] = a; + use_affinity = 1; + printf_verbose("Adding CPU %d affinity\n", a); + break; + case 'c': + if (argc < i + 2) { + show_usage(argc, argv); + return -1; + } + rduration = atol(argv[++i]); + break; + case 'd': + if (argc < i + 2) { + show_usage(argc, argv); + return -1; + } + wdelay = atol(argv[++i]); + break; + case 'v': + verbose_mode = 1; + break; + } + } + + printf_verbose("running test for %lu seconds, %u readers, %u writers.\n", + duration, nr_readers, nr_writers); + printf_verbose("Writer delay : %lu loops.\n", wdelay); + printf_verbose("Reader duration : %lu loops.\n", rduration); + printf_verbose("thread %-6s, thread id : %lx, tid %lu\n", + "main", pthread_self(), (unsigned long)gettid()); + + test_array = malloc(sizeof(*test_array) * ARRAY_SIZE); + tid_reader = malloc(sizeof(*tid_reader) * nr_readers); + tid_writer = malloc(sizeof(*tid_writer) * nr_writers); + count_reader = malloc(sizeof(*count_reader) * nr_readers); + count_writer = malloc(sizeof(*count_writer) * nr_writers); + + next_aff = 0; + + for (i = 0; i < nr_readers; i++) { + err = pthread_create(&tid_reader[i], NULL, thr_reader, + &count_reader[i]); + if (err != 0) + exit(1); + } + for (i = 0; i < nr_writers; i++) { + err = pthread_create(&tid_writer[i], NULL, thr_writer, + &count_writer[i]); + if (err != 0) + exit(1); + } + + smp_mb(); + + test_go = 1; + + sleep(duration); + + test_stop = 1; + + for (i = 0; i < nr_readers; i++) { + err = pthread_join(tid_reader[i], &tret); + if (err != 0) + exit(1); + tot_reads += count_reader[i]; + } + for (i = 0; i < nr_writers; i++) { + err = pthread_join(tid_writer[i], &tret); + if (err != 0) + exit(1); + tot_writes += count_writer[i]; + } + + printf_verbose("total number of reads : %llu, writes %llu\n", tot_reads, + tot_writes); + printf("SUMMARY %-25s testdur %4lu nr_readers %3u rdur %6lu " + "nr_writers %3u " + "wdelay %6lu nr_reads %12llu nr_writes %12llu nr_ops %12llu\n", + argv[0], duration, nr_readers, rduration, + nr_writers, wdelay, tot_reads, tot_writes, + tot_reads + tot_writes); + test_array_free(test_rcu_pointer); + free(test_array); + free(tid_reader); + free(tid_writer); + free(count_reader); + free(count_writer); + return 0; +} diff --git a/urcu-bp-static.h b/urcu-bp-static.h new file mode 100644 index 0000000..428c53f --- /dev/null +++ b/urcu-bp-static.h @@ -0,0 +1,197 @@ +#ifndef _URCU_BP_STATIC_H +#define _URCU_BP_STATIC_H + +/* + * urcu-bp-static.h + * + * Userspace RCU header. + * + * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking + * dynamically with the userspace rcu library. + * + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. + */ + +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +/* + * This code section can only be included in LGPL 2.1 compatible source code. + * See below for the function call wrappers which can be used in code meant to + * be only linked with the Userspace RCU library. This comes with a small + * performance degradation on the read-side due to the added function calls. + * This is required to permit relinking with newer versions of the library. + */ + +/* + * Active attempts to check for reader Q.S. before calling sleep(). + */ +#define RCU_QS_ACTIVE_ATTEMPTS 100 + +#ifdef DEBUG_RCU +#define rcu_assert(args...) assert(args) +#else +#define rcu_assert(args...) +#endif + +#ifdef DEBUG_YIELD +#include +#include +#include +#include + +#define YIELD_READ (1 << 0) +#define YIELD_WRITE (1 << 1) + +/* + * Updates without URCU_MB are much slower. Account this in + * the delay. + */ +/* maximum sleep delay, in us */ +#define MAX_SLEEP 50 + +extern unsigned int yield_active; +extern unsigned int __thread rand_yield; + +static inline void debug_yield_read(void) +{ + if (yield_active & YIELD_READ) + if (rand_r(&rand_yield) & 0x1) + usleep(rand_r(&rand_yield) % MAX_SLEEP); +} + +static inline void debug_yield_write(void) +{ + if (yield_active & YIELD_WRITE) + if (rand_r(&rand_yield) & 0x1) + usleep(rand_r(&rand_yield) % MAX_SLEEP); +} + +static inline void debug_yield_init(void) +{ + rand_yield = time(NULL) ^ pthread_self(); +} +#else +static inline void debug_yield_read(void) +{ +} + +static inline void debug_yield_write(void) +{ +} + +static inline void debug_yield_init(void) +{ + +} +#endif + +/* + * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a + * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits. + */ +#define RCU_GP_COUNT (1UL << 0) +/* Use the amount of bits equal to half of the architecture long size */ +#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2)) +#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1) + +/* + * Used internally by _rcu_read_lock. + */ +extern void rcu_bp_register(void); + +/* + * Global quiescent period counter with low-order bits unused. + * Using a int rather than a char to eliminate false register dependencies + * causing stalls on some architectures. + */ +extern long urcu_gp_ctr; + +struct urcu_reader { + /* Data used by both reader and synchronize_rcu() */ + long ctr; + /* Data used for registry */ + struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); + pthread_t tid; + int alloc; /* registry entry allocated */ +}; + +/* + * Bulletproof version keeps a pointer to a registry not part of the TLS. + * Adds a pointer dereference on the read-side, but won't require to unregister + * the reader thread. + */ +extern struct urcu_reader __thread *urcu_reader; + +static inline int rcu_old_gp_ongoing(long *value) +{ + long v; + + if (value == NULL) + return 0; + /* + * Make sure both tests below are done on the same version of *value + * to insure consistency. + */ + v = LOAD_SHARED(*value); + return (v & RCU_GP_CTR_NEST_MASK) && + ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT); +} + +static inline void _rcu_read_lock(void) +{ + long tmp; + + /* Check if registered */ + if (unlikely(!urcu_reader)) + rcu_bp_register(); + + tmp = urcu_reader->ctr; + /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */ + if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { + _STORE_SHARED(urcu_reader->ctr, _LOAD_SHARED(urcu_gp_ctr)); + /* + * Set active readers count for outermost nesting level before + * accessing the pointer. + */ + smp_mb(); + } else { + _STORE_SHARED(urcu_reader->ctr, tmp + RCU_GP_COUNT); + } +} + +static inline void _rcu_read_unlock(void) +{ + /* + * Finish using rcu before decrementing the pointer. + */ + smp_mb(); + _STORE_SHARED(urcu_reader->ctr, urcu_reader->ctr - RCU_GP_COUNT); +} + +#endif /* _URCU_BP_STATIC_H */ diff --git a/urcu-bp.c b/urcu-bp.c new file mode 100644 index 0000000..0fdf1f4 --- /dev/null +++ b/urcu-bp.c @@ -0,0 +1,362 @@ +/* + * urcu-bp.c + * + * Userspace RCU library, "bulletproof" version. + * + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "urcu-bp-static.h" +/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ +#include "urcu-bp.h" + +/* Sleep delay in us */ +#define RCU_SLEEP_DELAY 1000 +#define ARENA_INIT_ALLOC 16 + +void __attribute__((destructor)) urcu_bp_exit(void); + +static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER; + +#ifdef DEBUG_YIELD +unsigned int yield_active; +unsigned int __thread rand_yield; +#endif + +/* + * Global grace period counter. + * Contains the current RCU_GP_CTR_BIT. + * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. + * Written to only by writer with mutex taken. Read by both writer and readers. + */ +long urcu_gp_ctr = RCU_GP_COUNT; + +/* + * Pointer to registry elements. Written to only by each individual reader. Read + * by both the reader and the writers. + */ +struct urcu_reader __thread *urcu_reader; + +static LIST_HEAD(registry); + +struct registry_arena { + void *p; + size_t len; + size_t used; +}; + +static struct registry_arena registry_arena; + +static void rcu_gc_registry(void); + +static void internal_urcu_lock(void) +{ + int ret; + +#ifndef DISTRUST_SIGNALS_EXTREME + ret = pthread_mutex_lock(&urcu_mutex); + if (ret) { + perror("Error in pthread mutex lock"); + exit(-1); + } +#else /* #ifndef DISTRUST_SIGNALS_EXTREME */ + while ((ret = pthread_mutex_trylock(&urcu_mutex)) != 0) { + if (ret != EBUSY && ret != EINTR) { + printf("ret = %d, errno = %d\n", ret, errno); + perror("Error in pthread mutex lock"); + exit(-1); + } + if (urcu_reader.need_mb) { + smp_mb(); + urcu_reader.need_mb = 0; + smp_mb(); + } + poll(NULL,0,10); + } +#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ +} + +static void internal_urcu_unlock(void) +{ + int ret; + + ret = pthread_mutex_unlock(&urcu_mutex); + if (ret) { + perror("Error in pthread mutex unlock"); + exit(-1); + } +} + +/* + * called with urcu_mutex held. + */ +static void switch_next_urcu_qparity(void) +{ + STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT); +} + +void wait_for_quiescent_state(void) +{ + LIST_HEAD(qsreaders); + int wait_loops = 0; + struct urcu_reader *index, *tmp; + + if (list_empty(®istry)) + return; + /* + * Wait for each thread urcu_reader.ctr count to become 0. + */ + for (;;) { + wait_loops++; + list_for_each_entry_safe(index, tmp, ®istry, head) { + if (!rcu_old_gp_ongoing(&index->ctr)) + list_move(&index->head, &qsreaders); + } + + if (list_empty(®istry)) { + break; + } else { + if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) + usleep(RCU_SLEEP_DELAY); + else + cpu_relax(); + } + } + /* put back the reader list in the registry */ + list_splice(&qsreaders, ®istry); +} + +void synchronize_rcu(void) +{ + sigset_t newmask, oldmask; + int ret; + + ret = sigemptyset(&newmask); + assert(!ret); + ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); + assert(!ret); + + internal_urcu_lock(); + + /* Remove old registry elements */ + rcu_gc_registry(); + + /* All threads should read qparity before accessing data structure + * where new ptr points to. Must be done within internal_urcu_lock + * because it iterates on reader threads.*/ + /* Write new ptr before changing the qparity */ + smp_mb(); + + switch_next_urcu_qparity(); /* 0 -> 1 */ + + /* + * Must commit qparity update to memory before waiting for parity + * 0 quiescent state. Failure to do so could result in the writer + * waiting forever while new readers are always accessing data (no + * progress). + * Ensured by STORE_SHARED and LOAD_SHARED. + */ + + /* + * Adding a smp_mb() which is _not_ formally required, but makes the + * model easier to understand. It does not have a big performance impact + * anyway, given this is the write-side. + */ + smp_mb(); + + /* + * Wait for previous parity to be empty of readers. + */ + wait_for_quiescent_state(); /* Wait readers in parity 0 */ + + /* + * Must finish waiting for quiescent state for parity 0 before + * committing qparity update to memory. Failure to do so could result in + * the writer waiting forever while new readers are always accessing + * data (no progress). + * Ensured by STORE_SHARED and LOAD_SHARED. + */ + + /* + * Adding a smp_mb() which is _not_ formally required, but makes the + * model easier to understand. It does not have a big performance impact + * anyway, given this is the write-side. + */ + smp_mb(); + + switch_next_urcu_qparity(); /* 1 -> 0 */ + + /* + * Must commit qparity update to memory before waiting for parity + * 1 quiescent state. Failure to do so could result in the writer + * waiting forever while new readers are always accessing data (no + * progress). + * Ensured by STORE_SHARED and LOAD_SHARED. + */ + + /* + * Adding a smp_mb() which is _not_ formally required, but makes the + * model easier to understand. It does not have a big performance impact + * anyway, given this is the write-side. + */ + smp_mb(); + + /* + * Wait for previous parity to be empty of readers. + */ + wait_for_quiescent_state(); /* Wait readers in parity 1 */ + + /* Finish waiting for reader threads before letting the old ptr being + * freed. Must be done within internal_urcu_lock because it iterates on + * reader threads. */ + smp_mb(); + + internal_urcu_unlock(); + ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); + assert(!ret); +} + +/* + * library wrappers to be used by non-LGPL compatible source code. + */ + +void rcu_read_lock(void) +{ + _rcu_read_lock(); +} + +void rcu_read_unlock(void) +{ + _rcu_read_unlock(); +} + +/* + * only grow for now. + */ +static void resize_arena(struct registry_arena *arena, size_t len) +{ + void *new_arena; + + new_arena = mmap(arena->p, len, + PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, + -1, 0); + /* + * re-used the same region ? + */ + if (new_arena == arena->p) + return; + + memcpy(new_arena, arena->p, arena->len); + bzero(new_arena + arena->len, len - arena->len); + arena->p = new_arena; +} + +/* Called with signals off and mutex locked */ +static void add_thread(void) +{ + struct urcu_reader *urcu_reader_reg; + + if (registry_arena.len + < registry_arena.used + sizeof(struct urcu_reader)) + resize_arena(®istry_arena, + max(registry_arena.len << 1, ARENA_INIT_ALLOC)); + /* + * Find a free spot. + */ + for (urcu_reader_reg = registry_arena.p; + (void *)urcu_reader_reg < registry_arena.p + registry_arena.len; + urcu_reader_reg++) { + if (!urcu_reader_reg->alloc) + break; + } + urcu_reader_reg->alloc = 1; + registry_arena.used += sizeof(struct urcu_reader); + + /* Add to registry */ + urcu_reader_reg->tid = pthread_self(); + assert(urcu_reader_reg->ctr == 0); + list_add(&urcu_reader_reg->head, ®istry); + urcu_reader = urcu_reader_reg; +} + +/* Called with signals off and mutex locked */ +static void rcu_gc_registry(void) +{ + struct urcu_reader *urcu_reader_reg; + pthread_t tid; + int ret; + + for (urcu_reader_reg = registry_arena.p; + (void *)urcu_reader_reg < registry_arena.p + registry_arena.len; + urcu_reader_reg++) { + if (!urcu_reader_reg->alloc) + continue; + tid = urcu_reader_reg->tid; + ret = pthread_kill(tid, 0); + assert(ret != EINVAL); + if (ret == ESRCH) { + list_del(&urcu_reader_reg->head); + urcu_reader_reg->alloc = 0; + registry_arena.used -= sizeof(struct urcu_reader); + } + } +} + +/* Disable signals, take mutex, add to registry */ +void rcu_bp_register(void) +{ + sigset_t newmask, oldmask; + int ret; + + ret = sigemptyset(&newmask); + assert(!ret); + ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); + assert(!ret); + + /* + * Check if a signal concurrently registered our thread since + * the check in rcu_read_lock(). */ + if (urcu_reader) + goto end; + + internal_urcu_lock(); + add_thread(); + internal_urcu_unlock(); +end: + ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); + assert(!ret); +} + +void urcu_bp_exit() +{ + munmap(registry_arena.p, registry_arena.len); +} diff --git a/urcu-bp.h b/urcu-bp.h new file mode 100644 index 0000000..d42a2cb --- /dev/null +++ b/urcu-bp.h @@ -0,0 +1,100 @@ +#ifndef _URCU_BP_H +#define _URCU_BP_H + +/* + * urcu-bp.h + * + * Userspace RCU header, "bulletproof" version. + * + * Slower RCU read-side adapted for tracing library. Does not require thread + * registration nor unregistration. Also signal-safe. + * + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. + * + * LGPL-compatible code should include this header with : + * + * #define _LGPL_SOURCE + * #include + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. + */ + +#include +#include + +/* + * See urcu-pointer.h and urcu-pointer-static.h for pointer publication headers. + */ +#include + +/* + * Important ! + * + * Each thread containing read-side critical sections must be registered + * with rcu_register_thread() before calling rcu_read_lock(). + * rcu_unregister_thread() should be called before the thread exits. + */ + +#ifdef _LGPL_SOURCE + +#include + +/* + * Mappings for static use of the userspace RCU library. + * Should only be used in LGPL-compatible code. + */ + +/* + * rcu_read_lock() + * rcu_read_unlock() + * + * Mark the beginning and end of a read-side critical section. + */ +#define rcu_read_lock() _rcu_read_lock() +#define rcu_read_unlock() _rcu_read_unlock() + +#else /* !_LGPL_SOURCE */ + +/* + * library wrappers to be used by non-LGPL compatible source code. + * See LGPL-only urcu-pointer-static.h for documentation. + */ + +extern void rcu_read_lock(void); +extern void rcu_read_unlock(void); + +#endif /* !_LGPL_SOURCE */ + +extern void synchronize_rcu(void); + +/* + * In the bulletproof version, the following functions are no-ops. + */ +static inline void rcu_register_thread(void) +{ +} + +static inline void rcu_unregister_thread(void) +{ +} + +static inline void urcu_init(void) +{ +} + +#endif /* _URCU_BP_H */ diff --git a/urcu/compiler.h b/urcu/compiler.h index 4dd89ea..975e1ea 100644 --- a/urcu/compiler.h +++ b/urcu/compiler.h @@ -39,4 +39,12 @@ */ #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&x) +#ifndef max +#define max(a,b) ((a)>(b)?(a):(b)) +#endif + +#ifndef min +#define min(a,b) ((a)<(b)?(a):(b)) +#endif + #endif /* _URCU_COMPILER_H */