On Wed, 02/04 13:46, Paolo Bonzini wrote: > > > On 04/02/2015 04:42, Fam Zheng wrote: > > On Tue, 02/03 13:52, Paolo Bonzini wrote: > >> From: Mike Day <ncm...@ncultra.org> > >> > >> Add RCU-enabled variants on the existing bsd DQ facility. Each > >> operation has the same interface as the existing (non-RCU) > >> version. Also, each operation is implemented as macro. > >> > >> Using the RCU-enabled QLIST, existing QLIST users will be able to > >> convert to RCU without using a different list interface. > >> > >> Signed-off-by: Mike Day <ncm...@ncultra.org> > >> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > >> --- > >> hw/9pfs/virtio-9p-synth.c | 2 +- > >> include/qemu/queue.h | 11 -- > >> include/qemu/rcu_queue.h | 134 ++++++++++++++++++++ > >> tests/Makefile | 5 +- > >> tests/test-rcu-list.c | 306 > >> ++++++++++++++++++++++++++++++++++++++++++++++ > >> 5 files changed, 445 insertions(+), 13 deletions(-) > >> create mode 100644 include/qemu/rcu_queue.h > >> create mode 100644 tests/test-rcu-list.c > >> > >> diff --git a/hw/9pfs/virtio-9p-synth.c b/hw/9pfs/virtio-9p-synth.c > >> index e75aa87..a0ab9a8 100644 > >> --- a/hw/9pfs/virtio-9p-synth.c > >> +++ b/hw/9pfs/virtio-9p-synth.c > >> @@ -18,7 +18,7 @@ > >> #include "fsdev/qemu-fsdev.h" > >> #include "virtio-9p-synth.h" > >> #include "qemu/rcu.h" > >> - > >> +#include "qemu/rcu_queue.h" > >> #include <sys/stat.h> > >> > >> /* Root node for synth file system */ > >> diff --git a/include/qemu/queue.h b/include/qemu/queue.h > >> index c602797..8094150 100644 > >> --- a/include/qemu/queue.h > >> +++ b/include/qemu/queue.h > >> @@ -139,17 +139,6 @@ struct { > >> \ > >> (elm)->field.le_prev = &(head)->lh_first; \ > >> } while (/*CONSTCOND*/0) > >> > >> -#define QLIST_INSERT_HEAD_RCU(head, elm, field) do { \ > >> - (elm)->field.le_prev = &(head)->lh_first; \ > >> - (elm)->field.le_next = (head)->lh_first; \ > >> - smp_wmb(); /* fill elm before linking it */ \ > >> - if ((head)->lh_first != NULL) { \ > >> - (head)->lh_first->field.le_prev = &(elm)->field.le_next; \ > >> - } \ > >> - (head)->lh_first = (elm); \ > >> - smp_wmb(); \ > >> -} while (/* CONSTCOND*/0) > >> - > >> #define QLIST_REMOVE(elm, field) do { \ > >> if ((elm)->field.le_next != NULL) \ > >> (elm)->field.le_next->field.le_prev = \ > >> diff --git a/include/qemu/rcu_queue.h b/include/qemu/rcu_queue.h > >> new file mode 100644 > >> index 0000000..3aca7a5 > >> --- /dev/null > >> +++ b/include/qemu/rcu_queue.h > >> @@ -0,0 +1,134 @@ > >> +#ifndef QEMU_RCU_QUEUE_H > >> +#define QEMU_RCU_QUEUE_H > >> + > >> +/* > >> + * rcu_queue.h > >> + * > >> + * RCU-friendly versions of the queue.h primitives. > >> + * > >> + * 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 > >> + * > >> + * Copyright (c) 2013 Mike D. Day, IBM Corporation. > >> + * > >> + * IBM's contributions to this file may be relicensed under LGPLv2 or > >> later. > >> + */ > >> + > >> +#include "qemu/queue.h" > >> +#include "qemu/atomic.h" > >> + > >> +#ifdef __cplusplus > >> +extern "C" { > >> +#endif > >> + > >> + > >> +/* > >> + * List access methods. > >> + */ > >> +#define QLIST_EMPTY_RCU(head) (atomic_rcu_read(&(head)->lh_first) == NULL) > >> +#define QLIST_FIRST_RCU(head) (atomic_rcu_read(&(head)->lh_first)) > >> +#define QLIST_NEXT_RCU(elm, field) > >> (atomic_rcu_read(&(elm)->field.le_next)) > >> + > >> +/* > >> + * List functions. > >> + */ > >> + > >> + > >> +/* > >> + * The difference between atomic_read/set and atomic_rcu_read/set > >> + * is in the including of a read/write memory barrier to the volatile > >> + * access. atomic_rcu_* macros include the memory barrier, the > >> + * plain atomic macros do not. Therefore, it should be correct to > >> + * issue a series of reads or writes to the same element using only > >> + * the atomic_* macro, until the last read or write, which should be > >> + * atomic_rcu_* to introduce a read or write memory barrier as > >> + * appropriate. > >> + */ > >> + > >> +/* Upon publication of the listelm->next value, list readers > >> + * will see the new node when following next pointers from > >> + * antecedent nodes, but may not see the new node when following > >> + * prev pointers from subsequent nodes until after the RCU grace > >> + * period expires. > >> + * see linux/include/rculist.h __list_add_rcu(new, prev, next) > >> + */ > >> +#define QLIST_INSERT_AFTER_RCU(listelm, elm, field) do { \ > >> + (elm)->field.le_next = (listelm)->field.le_next; \ > >> + (elm)->field.le_prev = &(listelm)->field.le_next; \ > >> + atomic_rcu_set(&(listelm)->field.le_next, (elm)); \ > >> + if ((elm)->field.le_next != NULL) { \ > >> + (elm)->field.le_next->field.le_prev = \ > >> + &(elm)->field.le_next; \ > >> + } \ > >> +} while (/*CONSTCOND*/0) > >> + > >> +/* Upon publication of the listelm->prev->next value, list > >> + * readers will see the new element when following prev pointers > >> + * from subsequent elements, but may not see the new element > >> + * when following next pointers from antecedent elements > >> + * until after the RCU grace period expires. > >> + */ > >> +#define QLIST_INSERT_BEFORE_RCU(listelm, elm, field) do { \ > >> + (elm)->field.le_prev = (listelm)->field.le_prev; \ > >> + (elm)->field.le_next = (listelm); \ > >> + atomic_rcu_set((listelm)->field.le_prev, (elm)); \ > >> + (listelm)->field.le_prev = &(elm)->field.le_next; \ > >> +} while (/*CONSTCOND*/0) > >> + > >> +/* Upon publication of the head->first value, list readers > >> + * will see the new element when following the head, but may > >> + * not see the new element when following prev pointers from > >> + * subsequent elements until after the RCU grace period has > >> + * expired. > >> + */ > >> +#define QLIST_INSERT_HEAD_RCU(head, elm, field) do { \ > >> + (elm)->field.le_prev = &(head)->lh_first; \ > >> + (elm)->field.le_next = (head)->lh_first; \ > >> + atomic_rcu_set((&(head)->lh_first), (elm)); \ > >> + if ((elm)->field.le_next != NULL) { \ > >> + (elm)->field.le_next->field.le_prev = \ > >> + &(elm)->field.le_next; \ > >> + } \ > >> +} while (/*CONSTCOND*/0) > >> + > >> + > >> +/* prior to publication of the elm->prev->next value, some list > >> + * readers may still see the removed element when following > >> + * the antecedent's next pointer. > >> + */ > >> +#define QLIST_REMOVE_RCU(elm, field) do { \ > >> + if ((elm)->field.le_next != NULL) { \ > >> + (elm)->field.le_next->field.le_prev = \ > >> + (elm)->field.le_prev; \ > >> + } \ > >> + *(elm)->field.le_prev = (elm)->field.le_next; \ > >> +} while (/*CONSTCOND*/0) > >> + > >> +/* List traversal must occur within an RCU critical section. */ > >> +#define QLIST_FOREACH_RCU(var, head, field) \ > >> + for ((var) = atomic_rcu_read(&(head)->lh_first); \ > >> + (var); \ > >> + (var) = atomic_rcu_read(&(var)->field.le_next)) > >> + > >> +/* List traversal must occur within an RCU critical section. */ > >> +#define QLIST_FOREACH_SAFE_RCU(var, head, field, next_var) \ > >> + for ((var) = (atomic_rcu_read(&(head)->lh_first)); \ > >> + (var) && \ > >> + ((next_var) = atomic_rcu_read(&(var)->field.le_next), 1); \ > >> + (var) = (next_var)) > >> + > >> +#ifdef __cplusplus > >> +} > >> +#endif > >> +#endif /* QEMU_RCU_QUEUE.H */ > >> diff --git a/tests/Makefile b/tests/Makefile > >> index db5b3c3..ef8d589 100644 > >> --- a/tests/Makefile > >> +++ b/tests/Makefile > >> @@ -62,6 +62,8 @@ check-unit-y += tests/test-int128$(EXESUF) > >> gcov-files-test-int128-y = > >> check-unit-y += tests/rcutorture$(EXESUF) > >> gcov-files-rcutorture-y = util/rcu.c > >> +check-unit-y += tests/test-rcu-list$(EXESUF) > >> +gcov-files-test-rcu-list-y = util/rcu.c > >> check-unit-y += tests/test-bitops$(EXESUF) > >> check-unit-$(CONFIG_HAS_GLIB_SUBPROCESS_TESTS) += > >> tests/test-qdev-global-props$(EXESUF) > >> check-unit-y += tests/check-qom-interface$(EXESUF) > >> @@ -226,7 +228,7 @@ test-obj-y = tests/check-qint.o tests/check-qstring.o > >> tests/check-qdict.o \ > >> tests/test-qmp-commands.o tests/test-visitor-serialization.o \ > >> tests/test-x86-cpuid.o tests/test-mul64.o tests/test-int128.o \ > >> tests/test-opts-visitor.o tests/test-qmp-event.o \ > >> - tests/rcutorture.o > >> + tests/rcutorture.o tests/test-rcu-list.o > >> > >> test-qapi-obj-y = tests/test-qapi-visit.o tests/test-qapi-types.o \ > >> tests/test-qapi-event.o > >> @@ -256,6 +258,7 @@ tests/test-xbzrle$(EXESUF): tests/test-xbzrle.o > >> migration/xbzrle.o page_cache.o > >> tests/test-cutils$(EXESUF): tests/test-cutils.o util/cutils.o > >> tests/test-int128$(EXESUF): tests/test-int128.o > >> tests/rcutorture$(EXESUF): tests/rcutorture.o libqemuutil.a > >> +tests/test-rcu-list$(EXESUF): tests/test-rcu-list.o libqemuutil.a > >> > >> tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \ > >> hw/core/qdev.o hw/core/qdev-properties.o hw/core/hotplug.o\ > >> diff --git a/tests/test-rcu-list.c b/tests/test-rcu-list.c > >> new file mode 100644 > >> index 0000000..5ce55e9 > >> --- /dev/null > >> +++ b/tests/test-rcu-list.c > >> @@ -0,0 +1,306 @@ > >> +/* > >> + * rcuq_test.c > >> + * > >> + * usage: rcuq_test <readers> <duration> > >> + * > >> + * 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, > >> USA. > >> + * > >> + * Copyright (c) 2013 Mike D. Day, IBM Corporation. > >> + */ > >> + > >> +/* > >> + * Test variables. > >> + */ > > > > Move below the includes? > > > >> + > >> +#include <glib.h> > >> +#include <stdlib.h> > >> +#include <stdio.h> > >> +#include <string.h> > >> +#include "qemu/atomic.h" > >> +#include "qemu/rcu.h" > >> +#include "qemu/compiler.h" > >> +#include "qemu/osdep.h" > >> +#include "qemu/thread.h" > >> +#include "qemu/rcu_queue.h" > >> + > >> +long long n_reads = 0LL; > >> +long long n_updates = 0LL; > >> +long long n_reclaims = 0LL; > >> +long long n_nodes_removed = 0LL; > >> +long long n_nodes = 0LL; > >> +int g_test_in_charge = 0; > >> + > >> +int nthreadsrunning; > >> + > >> +char argsbuf[64]; > >> + > >> +#define GOFLAG_INIT 0 > >> +#define GOFLAG_RUN 1 > >> +#define GOFLAG_STOP 2 > >> + > >> +static volatile int goflag = GOFLAG_INIT; > >> + > >> +#define RCU_READ_RUN 1000 > >> +#define RCU_UPDATE_RUN 10 > >> +#define NR_THREADS 100 > >> +#define RCU_Q_LEN 100 > >> + > >> +static QemuThread threads[NR_THREADS]; > >> +static struct rcu_reader_data *data[NR_THREADS]; > >> +static int n_threads; > >> + > >> +static int select_random_el(int max) > >> +{ > >> + return (rand() % max); > >> +} > >> + > >> + > >> +static void create_thread(void *(*func)(void *)) > >> +{ > >> + if (n_threads >= NR_THREADS) { > >> + fprintf(stderr, "Thread limit of %d exceeded!\n", NR_THREADS); > >> + exit(-1); > >> + } > >> + qemu_thread_create(&threads[n_threads], "test", func, > >> &data[n_threads], > >> + QEMU_THREAD_JOINABLE); > >> + n_threads++; > >> +} > >> + > >> +static void wait_all_threads(void) > >> +{ > >> + int i; > >> + > >> + for (i = 0; i < n_threads; i++) { > >> + qemu_thread_join(&threads[i]); > >> + } > >> + n_threads = 0; > >> +} > >> + > >> + > >> +struct list_element { > >> + QLIST_ENTRY(list_element) entry; > >> + struct rcu_head rcu; > >> + long long val; > >> +}; > >> + > >> +static void reclaim_list_el(struct rcu_head *prcu) > >> +{ > >> + struct list_element *el = container_of(prcu, struct list_element, > >> rcu); > >> + g_free(el); > >> + atomic_add(&n_reclaims, 1); > >> +} > >> + > >> +static QLIST_HEAD(q_list_head, list_element) Q_list_head; > >> + > >> +static void *rcu_q_reader(void *arg) > >> +{ > >> + long long j, n_reads_local = 0; > >> + struct list_element *el; > >> + > >> + *(struct rcu_reader_data **)arg = &rcu_reader; > >> + atomic_inc(&nthreadsrunning); > >> + while (goflag == GOFLAG_INIT) { > >> + g_usleep(1000); > >> + } > >> + > >> + while (goflag == GOFLAG_RUN) { > >> + rcu_read_lock(); > >> + QLIST_FOREACH_RCU(el, &Q_list_head, entry) { > >> + j = atomic_read(&el->val); > >> + (void)j; > >> + n_reads_local++; > >> + if (goflag == GOFLAG_STOP) { > >> + break; > >> + } > >> + } > >> + rcu_read_unlock(); > >> + > >> + g_usleep(100); > >> + } > >> + atomic_add(&n_reads, n_reads_local); > >> + return NULL; > >> +} > >> + > >> + > >> +static void *rcu_q_updater(void *arg) > >> +{ > >> + int j, target_el; > >> + long long n_updates_local = 0; > >> + long long n_removed_local = 0; > >> + struct list_element *el, *prev_el; > >> + > >> + *(struct rcu_reader_data **)arg = &rcu_reader; > >> + atomic_inc(&nthreadsrunning); > >> + while (goflag == GOFLAG_INIT) { > >> + g_usleep(1000); > >> + } > >> + > >> + while (goflag == GOFLAG_RUN) { > >> + target_el = select_random_el(RCU_Q_LEN); > >> + j = 0; > >> + /* FOREACH_RCU could work here but let's use both macros */ > >> + QLIST_FOREACH_SAFE_RCU(prev_el, &Q_list_head, entry, el) { > >> + j++; > >> + if (target_el == j) { > >> + QLIST_REMOVE_RCU(prev_el, entry); > >> + /* may be more than one updater in the future */ > >> + call_rcu1(&prev_el->rcu, reclaim_list_el); > >> + n_removed_local++; > >> + break; > >> + } > >> + } > >> + if (goflag == GOFLAG_STOP) { > >> + break; > >> + } > >> + target_el = select_random_el(RCU_Q_LEN); > >> + j = 0; > >> + QLIST_FOREACH_RCU(el, &Q_list_head, entry) { > >> + j++; > >> + if (target_el == j) { > >> + prev_el = g_new(struct list_element, 1); > >> + atomic_add(&n_nodes, 1); > >> + prev_el->val = atomic_read(&n_nodes); > >> + QLIST_INSERT_BEFORE_RCU(el, prev_el, entry); > >> + break; > >> + } > >> + } > >> + > >> + n_updates_local += 2; > >> + synchronize_rcu(); > >> + } > >> + synchronize_rcu(); > > > > Is one of two synchronize_rcu's superfluous? Otherwise looks good: > > There is a "break"s in the loop, in that case the second synchronize_rcu > is necessary.
Oh yes. So my rev-by holds. Fam > > Paolo > > > > > Reviewed-by: Fam Zheng <f...@redhat.com> > > > >> + atomic_add(&n_updates, n_updates_local); > >> + atomic_add(&n_nodes_removed, n_removed_local); > >> + return NULL; > >> +} > > > > <...> > > > > >