[ltt-dev] [PATCH RFC] v3 call_rcu() interface for userspace-rcu
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Mon Feb 28 11:44:59 EST 2011
* Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote:
> Adds call_rcu(), with RCU threads to invoke the callbacks. By default,
> there will be one such RCU thread per process, created the first time
> that call_rcu() is invoked. On systems supporting sched_getcpu(), it
> is possible to create one RCU thread per CPU by calling
> create_all_cpu_call_rcu_data().
>
> This version includes a second round of feedback from Mathieu Desnoyers.
> In addition, the tests have been upgraded to randomly configure per-CPU
> and per-thread call_rcu() threads. In turn, the main code contains fixes
> for a number of embarrassing code that the resulting testing located.
>
> This version does not include changes to make valgrind happy.
> I am reviewing valgrind documentation to work out the best approach,
> and believe that there is a possible design that does not involve
> manually tearing everything down. More on that later.
BTW, are you planning to write a small update to the README file so people know
this new feature is available, and that they can call it from within RCU
read-side critical sections ? (contrarily to liburcu-defer) A section prior to
"Usage of liburcu-defer" called "Usage of liburcu-call-rcu" seems called for.
Thanks,
Mathieu
>
> However, this version does pass torture tests on a 48-CPU Power system
> (though I needed to re-apply the ppc asm typo fix).
>
> Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
>
> diff --git a/Makefile.am b/Makefile.am
> index 79a7152..7956e7e 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -1,6 +1,7 @@
> INCLUDES = -I$(top_builddir)/urcu
>
> AM_LDFLAGS=-lpthread
> +AM_CFLAGS=-Wall
>
> SUBDIRS = . tests
>
> @@ -29,8 +30,8 @@ COMPAT+=compat_futex.c
> endif
>
> lib_LTLIBRARIES = liburcu.la liburcu-qsbr.la liburcu-mb.la liburcu-signal.la \
> - liburcu-bp.la liburcu-defer.la libwfqueue.la libwfstack.la \
> - librculfqueue.la librculfstack.la
> + liburcu-bp.la liburcu-defer.la liburcu-call.la \
> + libwfqueue.la libwfstack.la librculfqueue.la librculfstack.la
>
> liburcu_la_SOURCES = urcu.c urcu-pointer.c $(COMPAT)
>
> @@ -44,6 +45,7 @@ liburcu_signal_la_CFLAGS = -DRCU_SIGNAL
>
> liburcu_bp_la_SOURCES = urcu-bp.c urcu-pointer.c $(COMPAT)
>
> +liburcu_call_la_SOURCES = urcu-call-rcu.c $(COMPAT)
> liburcu_defer_la_SOURCES = urcu-defer.c $(COMPAT)
>
> libwfqueue_la_SOURCES = wfqueue.c $(COMPAT)
> diff --git a/configure.ac b/configure.ac
> index 02780e7..88771d4 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -34,7 +34,7 @@ AC_TYPE_SIZE_T
> # Checks for library functions.
> AC_FUNC_MALLOC
> AC_FUNC_MMAP
> -AC_CHECK_FUNCS([bzero gettimeofday munmap strtoul])
> +AC_CHECK_FUNCS([bzero gettimeofday munmap sched_getcpu strtoul sysconf])
>
> # Find arch type
> case $host_cpu in
> diff --git a/tests/Makefile.am b/tests/Makefile.am
> index a43dd75..3c025a4 100644
> --- a/tests/Makefile.am
> +++ b/tests/Makefile.am
> @@ -1,5 +1,5 @@
> AM_LDFLAGS=-lpthread
> -AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir)
> +AM_CFLAGS=-I$(top_srcdir) -I$(top_builddir) -g
>
> noinst_PROGRAMS = test_urcu test_urcu_dynamic_link test_urcu_timing \
> test_urcu_signal test_urcu_signal_dynamic_link test_urcu_signal_timing \
> @@ -28,20 +28,21 @@ if COMPAT_FUTEX
> COMPAT+=$(top_srcdir)/compat_futex.c
> endif
>
> -URCU=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(COMPAT)
> -URCU_QSBR=$(top_srcdir)/urcu-qsbr.c $(top_srcdir)/urcu-pointer.c $(COMPAT)
> +URCU=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/urcu-call-rcu.c $(top_srcdir)/wfqueue.c $(COMPAT)
> +URCU_QSBR=$(top_srcdir)/urcu-qsbr.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/urcu-call-rcu.c $(top_srcdir)/wfqueue.c $(COMPAT)
> # URCU_MB uses urcu.c but -DRCU_MB must be defined
> -URCU_MB=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(COMPAT)
> +URCU_MB=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/urcu-call-rcu.c $(top_srcdir)/wfqueue.c $(COMPAT)
> # URCU_SIGNAL uses urcu.c but -DRCU_SIGNAL must be defined
> -URCU_SIGNAL=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(COMPAT)
> -URCU_BP=$(top_srcdir)/urcu-bp.c $(top_srcdir)/urcu-pointer.c $(COMPAT)
> -URCU_DEFER=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-defer.c $(top_srcdir)/urcu-pointer.c $(COMPAT)
> +URCU_SIGNAL=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/urcu-call-rcu.c $(top_srcdir)/wfqueue.c $(COMPAT)
> +URCU_BP=$(top_srcdir)/urcu-bp.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/urcu-call-rcu.c $(top_srcdir)/wfqueue.c $(COMPAT)
> +URCU_DEFER=$(top_srcdir)/urcu.c $(top_srcdir)/urcu-defer.c $(top_srcdir)/urcu-pointer.c $(top_srcdir)/urcu-call-rcu.c $(top_srcdir)/wfqueue.c $(COMPAT)
>
> URCU_LIB=$(top_builddir)/liburcu.la
> URCU_QSBR_LIB=$(top_builddir)/liburcu-qsbr.la
> URCU_MB_LIB=$(top_builddir)/liburcu-mb.la
> URCU_SIGNAL_LIB=$(top_builddir)/liburcu-signal.la
> URCU_BP_LIB=$(top_builddir)/liburcu-bp.la
> +URCU_CALL_LIB=$(top_builddir)/liburcu-call.la
> WFQUEUE_LIB=$(top_builddir)/libwfqueue.la
> WFSTACK_LIB=$(top_builddir)/libwfstack.la
> RCULFQUEUE_LIB=$(top_builddir)/librculfqueue.la
> @@ -95,23 +96,23 @@ test_perthreadlock_SOURCES = test_perthreadlock.c $(URCU_SIGNAL)
>
> rcutorture_urcu_SOURCES = urcutorture.c
> rcutorture_urcu_CFLAGS = -DTORTURE_URCU $(AM_CFLAGS)
> -rcutorture_urcu_LDADD = $(URCU)
> +rcutorture_urcu_LDADD = $(URCU) $(URCU_CALL_LIB) $(WFQUEUE_LIB)
>
> rcutorture_urcu_mb_SOURCES = urcutorture.c
> rcutorture_urcu_mb_CFLAGS = -DTORTURE_URCU_MB $(AM_CFLAGS)
> -rcutorture_urcu_mb_LDADD = $(URCU_MB_LIB)
> +rcutorture_urcu_mb_LDADD = $(URCU_MB_LIB) $(URCU_CALL_LIB) $(WFQUEUE_LIB)
>
> rcutorture_qsbr_SOURCES = urcutorture.c
> rcutorture_qsbr_CFLAGS = -DTORTURE_QSBR $(AM_CFLAGS)
> -rcutorture_qsbr_LDADD = $(URCU_QSBR_LIB)
> +rcutorture_qsbr_LDADD = $(URCU_QSBR_LIB) $(URCU_CALL_LIB) $(WFQUEUE_LIB)
>
> rcutorture_urcu_signal_SOURCES = urcutorture.c
> rcutorture_urcu_signal_CFLAGS = -DTORTURE_URCU_SIGNAL $(AM_CFLAGS)
> -rcutorture_urcu_signal_LDADD = $(URCU_SIGNAL_LIB)
> +rcutorture_urcu_signal_LDADD = $(URCU_SIGNAL_LIB) $(URCU_CALL_LIB) $(WFQUEUE_LIB)
>
> rcutorture_urcu_bp_SOURCES = urcutorture.c
> rcutorture_urcu_bp_CFLAGS = -DTORTURE_URCU_BP $(AM_CFLAGS)
> -rcutorture_urcu_bp_LDADD = $(URCU_BP_LIB)
> +rcutorture_urcu_bp_LDADD = $(URCU_BP_LIB) $(URCU_CALL_LIB) $(WFQUEUE_LIB)
>
> test_mutex_SOURCES = test_mutex.c $(URCU)
>
> diff --git a/tests/rcutorture.h b/tests/rcutorture.h
> index 4dac2f2..b42b8ab 100644
> --- a/tests/rcutorture.h
> +++ b/tests/rcutorture.h
> @@ -65,6 +65,9 @@
> * Test variables.
> */
>
> +#include <stdlib.h>
> +#include "../urcu-call-rcu.h"
> +
> DEFINE_PER_THREAD(long long, n_reads_pt);
> DEFINE_PER_THREAD(long long, n_updates_pt);
>
> @@ -147,6 +150,16 @@ void *rcu_update_perf_test(void *arg)
> {
> long long n_updates_local = 0;
>
> + if ((random() & 0xf00) == 0) {
> + struct call_rcu_data *crdp;
> +
> + crdp = create_call_rcu_data(0);
> + if (crdp != NULL) {
> + fprintf(stderr,
> + "Using per-thread call_rcu() worker.\n");
> + set_thread_call_rcu_data(crdp);
> + }
> + }
> uatomic_inc(&nthreadsrunning);
> while (goflag == GOFLAG_INIT)
> poll(NULL, 0, 1);
> @@ -296,10 +309,30 @@ void *rcu_read_stress_test(void *arg)
> return (NULL);
> }
>
> +static pthread_mutex_t call_rcu_test_mutex = PTHREAD_MUTEX_INITIALIZER;
> +static pthread_cond_t call_rcu_test_cond = PTHREAD_COND_INITIALIZER;
> +
> +void rcu_update_stress_test_rcu(struct rcu_head *head)
> +{
> + if (pthread_mutex_lock(&call_rcu_test_mutex) != 0) {
> + perror("pthread_mutex_lock");
> + exit(-1);
> + }
> + if (pthread_cond_signal(&call_rcu_test_cond) != 0) {
> + perror("pthread_cond_signal");
> + exit(-1);
> + }
> + if (pthread_mutex_unlock(&call_rcu_test_mutex) != 0) {
> + perror("pthread_mutex_unlock");
> + exit(-1);
> + }
> +}
> +
> void *rcu_update_stress_test(void *arg)
> {
> int i;
> struct rcu_stress *p;
> + struct rcu_head rh;
>
> while (goflag == GOFLAG_INIT)
> poll(NULL, 0, 1);
> @@ -317,7 +350,24 @@ void *rcu_update_stress_test(void *arg)
> for (i = 0; i < RCU_STRESS_PIPE_LEN; i++)
> if (i != rcu_stress_idx)
> rcu_stress_array[i].pipe_count++;
> - synchronize_rcu();
> + if (n_updates & 0x1)
> + synchronize_rcu();
> + else {
> + if (pthread_mutex_lock(&call_rcu_test_mutex) != 0) {
> + perror("pthread_mutex_lock");
> + exit(-1);
> + }
> + call_rcu(&rh, rcu_update_stress_test_rcu);
> + if (pthread_cond_wait(&call_rcu_test_cond,
> + &call_rcu_test_mutex) != 0) {
> + perror("pthread_cond_wait");
> + exit(-1);
> + }
> + if (pthread_mutex_unlock(&call_rcu_test_mutex) != 0) {
> + perror("pthread_mutex_unlock");
> + exit(-1);
> + }
> + }
> n_updates++;
> }
> return NULL;
> @@ -325,6 +375,16 @@ void *rcu_update_stress_test(void *arg)
>
> void *rcu_fake_update_stress_test(void *arg)
> {
> + if ((random() & 0xf00) == 0) {
> + struct call_rcu_data *crdp;
> +
> + crdp = create_call_rcu_data(0);
> + if (crdp != NULL) {
> + fprintf(stderr,
> + "Using per-thread call_rcu() worker.\n");
> + set_thread_call_rcu_data(crdp);
> + }
> + }
> while (goflag == GOFLAG_INIT)
> poll(NULL, 0, 1);
> while (goflag == GOFLAG_RUN) {
> @@ -396,6 +456,12 @@ int main(int argc, char *argv[])
>
> smp_init();
> //rcu_init();
> + srandom(time(NULL));
> + if (random() & 0x100) {
> + fprintf(stderr, "Allocating per-CPU call_rcu threads.\n");
> + if (create_all_cpu_call_rcu_data(0))
> + perror("create_all_cpu_call_rcu_data");
> + }
>
> #ifdef DEBUG_YIELD
> yield_active |= YIELD_READ;
> diff --git a/urcu-call-rcu.c b/urcu-call-rcu.c
> new file mode 100644
> index 0000000..5c003aa
> --- /dev/null
> +++ b/urcu-call-rcu.c
> @@ -0,0 +1,450 @@
> +/*
> + * urcu-call-rcu.c
> + *
> + * Userspace RCU library - batch memory reclamation with kernel API
> + *
> + * Copyright (c) 2010 Paul E. McKenney <paulmck at linux.vnet.ibm.com>
> + *
> + * 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
> + */
> +
> +#include <stdio.h>
> +#include <pthread.h>
> +#include <signal.h>
> +#include <assert.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <errno.h>
> +#include <poll.h>
> +#include <sys/time.h>
> +#include <syscall.h>
> +#include <unistd.h>
> +
> +#include "config.h"
> +#include "urcu/wfqueue.h"
> +#include "urcu-call-rcu.h"
> +#include "urcu-pointer.h"
> +
> +/* Data structure that identifies a call_rcu thread. */
> +
> +struct call_rcu_data {
> + struct cds_wfq_queue cbs;
> + unsigned long flags;
> + pthread_mutex_t mtx;
> + pthread_cond_t cond;
> + unsigned long qlen;
> + pthread_t tid;
> +} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
> +
> +/* Link a thread using call_rcu() to its call_rcu thread. */
> +
> +static __thread struct call_rcu_data *thread_call_rcu_data;
> +
> +/* Guard call_rcu thread creation. */
> +
> +static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
> +
> +/* If a given thread does not have its own call_rcu thread, this is default. */
> +
> +static struct call_rcu_data *default_call_rcu_data;
> +
> +extern void synchronize_rcu(void);
> +
> +/*
> + * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
> + * available, then we can have call_rcu threads assigned to individual
> + * CPUs rather than only to specific threads.
> + */
> +
> +#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
> +
> +/*
> + * Pointer to array of pointers to per-CPU call_rcu_data structures
> + * and # CPUs.
> + */
> +
> +static struct call_rcu_data **per_cpu_call_rcu_data;
> +static long maxcpus;
> +
> +/* Allocate the array if it has not already been allocated. */
> +
> +static void alloc_cpu_call_rcu_data(void)
> +{
> + struct call_rcu_data **p;
> + static int warned = 0;
> +
> + if (maxcpus != 0)
> + return;
> + maxcpus = sysconf(_SC_NPROCESSORS_CONF);
> + if (maxcpus <= 0) {
> + return;
> + }
> + p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
> + if (p != NULL) {
> + memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
> + per_cpu_call_rcu_data = p;
> + } else {
> + if (!warned) {
> + fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
> + }
> + warned = 1;
> + }
> +}
> +
> +#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
> +
> +static const struct call_rcu_data **per_cpu_call_rcu_data = NULL;
> +static const long maxcpus = -1;
> +
> +static void alloc_cpu_call_rcu_data(void)
> +{
> +}
> +
> +static int sched_getcpu(void)
> +{
> + return -1;
> +}
> +
> +#endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
> +
> +/* Acquire the specified pthread mutex. */
> +
> +static void call_rcu_lock(pthread_mutex_t *pmp)
> +{
> + if (pthread_mutex_lock(pmp) != 0) {
> + perror("pthread_mutex_lock");
> + exit(-1);
> + }
> +}
> +
> +/* Release the specified pthread mutex. */
> +
> +static void call_rcu_unlock(pthread_mutex_t *pmp)
> +{
> + if (pthread_mutex_unlock(pmp) != 0) {
> + perror("pthread_mutex_unlock");
> + exit(-1);
> + }
> +}
> +
> +/* This is the code run by each call_rcu thread. */
> +
> +static void *call_rcu_thread(void *arg)
> +{
> + unsigned long cbcount;
> + struct cds_wfq_node *cbs;
> + struct cds_wfq_node **cbs_tail;
> + struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
> + struct rcu_head *rhp;
> +
> + thread_call_rcu_data = crdp;
> + for (;;) {
> + if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
> + while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
> + poll(NULL, 0, 1);
> + _CMM_STORE_SHARED(crdp->cbs.head, NULL);
> + cbs_tail = (struct cds_wfq_node **)
> + uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
> + synchronize_rcu();
> + cbcount = 0;
> + do {
> + while (cbs->next == NULL &&
> + &cbs->next != cbs_tail)
> + poll(NULL, 0, 1);
> + if (cbs == &crdp->cbs.dummy) {
> + cbs = cbs->next;
> + continue;
> + }
> + rhp = (struct rcu_head *)cbs;
> + cbs = cbs->next;
> + rhp->func(rhp);
> + cbcount++;
> + } while (cbs != NULL);
> + uatomic_sub(&crdp->qlen, cbcount);
> + }
> + if (crdp->flags & URCU_CALL_RCU_RT)
> + poll(NULL, 0, 10);
> + else {
> + call_rcu_lock(&crdp->mtx);
> + _CMM_STORE_SHARED(crdp->flags,
> + crdp->flags & ~URCU_CALL_RCU_RUNNING);
> + if (&crdp->cbs.head ==
> + _CMM_LOAD_SHARED(crdp->cbs.tail) &&
> + pthread_cond_wait(&crdp->cond, &crdp->mtx) != 0) {
> + perror("pthread_cond_wait");
> + exit(-1);
> + }
> + _CMM_STORE_SHARED(crdp->flags,
> + crdp->flags | URCU_CALL_RCU_RUNNING);
> + poll(NULL, 0, 10);
> + call_rcu_unlock(&crdp->mtx);
> + }
> + }
> + return NULL; /* NOTREACHED */
> +}
> +
> +/*
> + * Create both a call_rcu thread and the corresponding call_rcu_data
> + * structure, linking the structure in as specified.
> + */
> +
> +void call_rcu_data_init(struct call_rcu_data **crdpp, unsigned long flags)
> +{
> + struct call_rcu_data *crdp;
> +
> + crdp = malloc(sizeof(*crdp));
> + if (crdp == NULL) {
> + fprintf(stderr, "Out of memory.\n");
> + exit(-1);
> + }
> + memset(crdp, '\0', sizeof(*crdp));
> + cds_wfq_init(&crdp->cbs);
> + crdp->qlen = 0;
> + if (pthread_mutex_init(&crdp->mtx, NULL) != 0) {
> + perror("pthread_mutex_init");
> + exit(-1);
> + }
> + if (pthread_cond_init(&crdp->cond, NULL) != 0) {
> + perror("pthread_cond_init");
> + exit(-1);
> + }
> + crdp->flags = flags | URCU_CALL_RCU_RUNNING;
> + cmm_smp_mb(); /* Structure initialized before pointer is planted. */
> + *crdpp = crdp;
> + if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) {
> + perror("pthread_create");
> + exit(-1);
> + }
> +}
> +
> +/*
> + * Return a pointer to the call_rcu_data structure for the specified
> + * CPU, returning NULL if there is none. We cannot automatically
> + * created it because the platform we are running on might not define
> + * sched_getcpu().
> + */
> +
> +struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
> +{
> + static int warned = 0;
> +
> + if (per_cpu_call_rcu_data == NULL)
> + return NULL;
> + if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
> + fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
> + warned = 1;
> + }
> + if (cpu < 0 || maxcpus <= cpu)
> + return NULL;
> + return per_cpu_call_rcu_data[cpu];
> +}
> +
> +/*
> + * Return the tid corresponding to the call_rcu thread whose
> + * call_rcu_data structure is specified.
> + */
> +
> +pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
> +{
> + return crdp->tid;
> +}
> +
> +/*
> + * Create a call_rcu_data structure (with thread) and return a pointer.
> + */
> +
> +struct call_rcu_data *create_call_rcu_data(unsigned long flags)
> +{
> + struct call_rcu_data *crdp;
> +
> + call_rcu_data_init(&crdp, flags);
> + return crdp;
> +}
> +
> +/*
> + * Set the specified CPU to use the specified call_rcu_data structure.
> + */
> +
> +int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
> +{
> + int warned = 0;
> +
> + call_rcu_lock(&call_rcu_mutex);
> + if (cpu < 0 || maxcpus <= cpu) {
> + if (!warned) {
> + fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
> + warned = 1;
> + }
> + call_rcu_unlock(&call_rcu_mutex);
> + errno = EINVAL;
> + return -EINVAL;
> + }
> + alloc_cpu_call_rcu_data();
> + call_rcu_unlock(&call_rcu_mutex);
> + if (per_cpu_call_rcu_data == NULL) {
> + errno = ENOMEM;
> + return -ENOMEM;
> + }
> + per_cpu_call_rcu_data[cpu] = crdp;
> + return 0;
> +}
> +
> +/*
> + * Return a pointer to the default call_rcu_data structure, creating
> + * one if need be. Because we never free call_rcu_data structures,
> + * we don't need to be in an RCU read-side critical section.
> + */
> +
> +struct call_rcu_data *get_default_call_rcu_data(void)
> +{
> + if (default_call_rcu_data != NULL)
> + return rcu_dereference(default_call_rcu_data);
> + call_rcu_lock(&call_rcu_mutex);
> + if (default_call_rcu_data != NULL) {
> + call_rcu_unlock(&call_rcu_mutex);
> + return default_call_rcu_data;
> + }
> + call_rcu_data_init(&default_call_rcu_data, 0);
> + call_rcu_unlock(&call_rcu_mutex);
> + return default_call_rcu_data;
> +}
> +
> +/*
> + * Return the call_rcu_data structure that applies to the currently
> + * running thread. Any call_rcu_data structure assigned specifically
> + * to this thread has first priority, followed by any call_rcu_data
> + * structure assigned to the CPU on which the thread is running,
> + * followed by the default call_rcu_data structure. If there is not
> + * yet a default call_rcu_data structure, one will be created.
> + */
> +struct call_rcu_data *get_call_rcu_data(void)
> +{
> + int curcpu;
> + static int warned = 0;
> +
> + if (thread_call_rcu_data != NULL)
> + return thread_call_rcu_data;
> + if (maxcpus <= 0)
> + return get_default_call_rcu_data();
> + curcpu = sched_getcpu();
> + if (!warned && (curcpu < 0 || maxcpus <= curcpu)) {
> + fprintf(stderr, "[error] liburcu: gcrd CPU # out of range\n");
> + warned = 1;
> + }
> + if (curcpu >= 0 && maxcpus > curcpu &&
> + per_cpu_call_rcu_data != NULL &&
> + per_cpu_call_rcu_data[curcpu] != NULL)
> + return per_cpu_call_rcu_data[curcpu];
> + return get_default_call_rcu_data();
> +}
> +
> +/*
> + * Return a pointer to this task's call_rcu_data if there is one.
> + */
> +
> +struct call_rcu_data *get_thread_call_rcu_data(void)
> +{
> + return thread_call_rcu_data;
> +}
> +
> +/*
> + * Set this task's call_rcu_data structure as specified, regardless
> + * of whether or not this task already had one. (This allows switching
> + * to and from real-time call_rcu threads, for example.)
> + */
> +
> +void set_thread_call_rcu_data(struct call_rcu_data *crdp)
> +{
> + thread_call_rcu_data = crdp;
> +}
> +
> +/*
> + * Create a separate call_rcu thread for each CPU. This does not
> + * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
> + * function if you want that behavior.
> + */
> +
> +int create_all_cpu_call_rcu_data(unsigned long flags)
> +{
> + int i;
> + struct call_rcu_data *crdp;
> + int ret;
> +
> + call_rcu_lock(&call_rcu_mutex);
> + alloc_cpu_call_rcu_data();
> + call_rcu_unlock(&call_rcu_mutex);
> + if (maxcpus <= 0) {
> + errno = EINVAL;
> + return -EINVAL;
> + }
> + if (per_cpu_call_rcu_data == NULL) {
> + errno = ENOMEM;
> + return -ENOMEM;
> + }
> + for (i = 0; i < maxcpus; i++) {
> + call_rcu_lock(&call_rcu_mutex);
> + if (get_cpu_call_rcu_data(i)) {
> + call_rcu_unlock(&call_rcu_mutex);
> + continue;
> + }
> + crdp = create_call_rcu_data(flags);
> + if (crdp == NULL) {
> + call_rcu_unlock(&call_rcu_mutex);
> + errno = ENOMEM;
> + return -ENOMEM;
> + }
> + call_rcu_unlock(&call_rcu_mutex);
> + if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
> + /* FIXME: Leaks crdp for now. */
> + return ret; /* Can happen on race. */
> + }
> + }
> + return 0;
> +}
> +
> +/*
> + * Schedule a function to be invoked after a following grace period.
> + * This is the only function that must be called -- the others are
> + * only present to allow applications to tune their use of RCU for
> + * maximum performance.
> + *
> + * Note that unless a call_rcu thread has not already been created,
> + * the first invocation of call_rcu() will create one. So, if you
> + * need the first invocation of call_rcu() to be fast, make sure
> + * to create a call_rcu thread first. One way to accomplish this is
> + * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
> + */
> +
> +void call_rcu(struct rcu_head *head,
> + void (*func)(struct rcu_head *head))
> +{
> + struct call_rcu_data *crdp;
> +
> + cds_wfq_node_init(&head->next);
> + head->func = func;
> + crdp = get_call_rcu_data();
> + cds_wfq_enqueue(&crdp->cbs, &head->next);
> + uatomic_inc(&crdp->qlen);
> + if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) {
> + call_rcu_lock(&crdp->mtx);
> + if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RUNNING)) {
> + if (pthread_cond_signal(&crdp->cond) != 0) {
> + perror("pthread_cond_signal");
> + exit(-1);
> + }
> + }
> + call_rcu_unlock(&crdp->mtx);
> + }
> +}
> diff --git a/urcu-call-rcu.h b/urcu-call-rcu.h
> new file mode 100644
> index 0000000..2c13388
> --- /dev/null
> +++ b/urcu-call-rcu.h
> @@ -0,0 +1,80 @@
> +#ifndef _URCU_CALL_RCU_H
> +#define _URCU_CALL_RCU_H
> +
> +/*
> + * urcu-call-rcu.h
> + *
> + * Userspace RCU header - deferred execution
> + *
> + * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
> + *
> + * LGPL-compatible code should include this header with :
> + *
> + * #define _LGPL_SOURCE
> + * #include <urcu-defer.h>
> + *
> + * 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
> + */
> +
> +#include <stdlib.h>
> +#include <pthread.h>
> +
> +#include <urcu/wfqueue.h>
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +/* Note that struct call_rcu_data is opaque to callers. */
> +
> +struct call_rcu_data;
> +
> +/* Flag values. */
> +
> +#define URCU_CALL_RCU_RT 0x1
> +#define URCU_CALL_RCU_RUNNING 0x2
> +
> +/*
> + * The rcu_head data structure is placed in the structure to be freed
> + * via call_rcu().
> + */
> +
> +struct rcu_head {
> + struct cds_wfq_node next;
> + void (*func)(struct rcu_head *head);
> +};
> +
> +/*
> + * Exported functions
> + */
> +void call_rcu_data_init(struct call_rcu_data **crdpp, unsigned long flags);
> +struct call_rcu_data *get_cpu_call_rcu_data(int cpu);
> +pthread_t get_call_rcu_thread(struct call_rcu_data *crdp);
> +struct call_rcu_data *create_call_rcu_data(unsigned long flags);
> +int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp);
> +struct call_rcu_data *get_default_call_rcu_data(void);
> +struct call_rcu_data *get_call_rcu_data(void);
> +struct call_rcu_data *get_thread_call_rcu_data(void);
> +void set_thread_call_rcu_data(struct call_rcu_data *crdp);
> +int create_all_cpu_call_rcu_data(unsigned long flags);
> +void call_rcu(struct rcu_head *head,
> + void (*func)(struct rcu_head *head));
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _URCU_CALL_RCU_H */
> diff --git a/urcu-defer.h b/urcu-defer.h
> index e161616..a64c75c 100644
> --- a/urcu-defer.h
> +++ b/urcu-defer.h
> @@ -53,14 +53,6 @@ extern "C" {
> extern void defer_rcu(void (*fct)(void *p), void *p);
>
> /*
> - * call_rcu will eventually be implemented with an API similar to the Linux
> - * kernel call_rcu(), which will allow its use within RCU read-side C.S.
> - * Generate an error if used for now.
> - */
> -
> -#define call_rcu __error_call_rcu_not_implemented_please_use_defer_rcu
> -
> -/*
> * Thread registration for reclamation.
> */
> extern void rcu_defer_register_thread(void);
> diff --git a/urcu/wfqueue-static.h b/urcu/wfqueue-static.h
> index 30d6e96..790931b 100644
> --- a/urcu/wfqueue-static.h
> +++ b/urcu/wfqueue-static.h
> @@ -28,6 +28,7 @@
>
> #include <pthread.h>
> #include <assert.h>
> +#include <poll.h>
> #include <urcu/compiler.h>
> #include <urcu/uatomic_arch.h>
>
> @@ -47,12 +48,12 @@ extern "C" {
> #define WFQ_ADAPT_ATTEMPTS 10 /* Retry if being set */
> #define WFQ_WAIT 10 /* Wait 10 ms if being set */
>
> -void _cds_wfq_node_init(struct cds_wfq_node *node)
> +static inline void _cds_wfq_node_init(struct cds_wfq_node *node)
> {
> node->next = NULL;
> }
>
> -void _cds_wfq_init(struct cds_wfq_queue *q)
> +static inline void _cds_wfq_init(struct cds_wfq_queue *q)
> {
> int ret;
>
> @@ -64,7 +65,8 @@ void _cds_wfq_init(struct cds_wfq_queue *q)
> assert(!ret);
> }
>
> -void _cds_wfq_enqueue(struct cds_wfq_queue *q, struct cds_wfq_node *node)
> +static inline void _cds_wfq_enqueue(struct cds_wfq_queue *q,
> + struct cds_wfq_node *node)
> {
> struct cds_wfq_node **old_tail;
>
> @@ -90,7 +92,7 @@ void _cds_wfq_enqueue(struct cds_wfq_queue *q, struct cds_wfq_node *node)
> * thread to be scheduled. The queue appears empty until tail->next is set by
> * enqueue.
> */
> -struct cds_wfq_node *
> +static inline struct cds_wfq_node *
> ___cds_wfq_dequeue_blocking(struct cds_wfq_queue *q)
> {
> struct cds_wfq_node *node, *next;
> @@ -128,7 +130,7 @@ ___cds_wfq_dequeue_blocking(struct cds_wfq_queue *q)
> return node;
> }
>
> -struct cds_wfq_node *
> +static inline struct cds_wfq_node *
> _cds_wfq_dequeue_blocking(struct cds_wfq_queue *q)
> {
> struct cds_wfq_node *retnode;
> diff --git a/urcu/wfstack-static.h b/urcu/wfstack-static.h
> index eed83da..ff18c4a 100644
> --- a/urcu/wfstack-static.h
> +++ b/urcu/wfstack-static.h
> @@ -28,6 +28,7 @@
>
> #include <pthread.h>
> #include <assert.h>
> +#include <poll.h>
> #include <urcu/compiler.h>
> #include <urcu/uatomic_arch.h>
>
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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