From: Mathieu Desnoyers Date: Tue, 30 May 2017 19:14:58 +0000 (-0400) Subject: Implement urcu workqueues internal API X-Git-Tag: v0.10.0~4 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ccacf27fd8d1af069016d7cf3a91f8995af08b8c;p=urcu.git Implement urcu workqueues internal API Signed-off-by: Mathieu Desnoyers --- diff --git a/src/Makefile.am b/src/Makefile.am index a801020..60b833d 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -54,7 +54,7 @@ liburcu_bp_la_SOURCES = urcu-bp.c urcu-pointer.c $(COMPAT) liburcu_bp_la_LIBADD = liburcu-common.la liburcu_cds_la_SOURCES = rculfqueue.c rculfstack.c lfstack.c \ - $(RCULFHASH) $(COMPAT) + workqueue.c workqueue.h $(RCULFHASH) $(COMPAT) liburcu_cds_la_LIBADD = liburcu-common.la pkgconfigdir = $(libdir)/pkgconfig diff --git a/src/workqueue.c b/src/workqueue.c new file mode 100644 index 0000000..17ea835 --- /dev/null +++ b/src/workqueue.c @@ -0,0 +1,472 @@ +/* + * workqueue.c + * + * Userspace RCU library - Userspace workqeues + * + * Copyright (c) 2010 Paul E. McKenney + * Copyright (c) 2017 Mathieu Desnoyers + * + * 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 + */ + +#define _LGPL_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "compat-getcpu.h" +#include "urcu/wfcqueue.h" +#include "urcu-call-rcu.h" +#include "urcu-pointer.h" +#include "urcu/list.h" +#include "urcu/futex.h" +#include "urcu/tls-compat.h" +#include "urcu/ref.h" +#include "urcu-die.h" + +#include "workqueue.h" + +#define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */ +#define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1) + +/* Data structure that identifies a workqueue. */ + +struct urcu_workqueue { + /* + * We do not align head on a different cache-line than tail + * mainly because call_rcu callback-invocation threads use + * batching ("splice") to get an entire list of callbacks, which + * effectively empties the queue, and requires to touch the tail + * anyway. + */ + struct cds_wfcq_tail cbs_tail; + struct cds_wfcq_head cbs_head; + unsigned long flags; + int32_t futex; + unsigned long qlen; /* maintained for debugging. */ + pthread_t tid; + int cpu_affinity; + unsigned long loop_count; + void *priv; + void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv); + void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv); + void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv); + void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv); + void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv); + void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv); + void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv); +} __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + +struct urcu_workqueue_completion { + int barrier_count; + int32_t futex; + struct urcu_ref ref; +}; + +struct urcu_workqueue_completion_work { + struct urcu_work work; + struct urcu_workqueue_completion *completion; +}; + +/* + * Periodically retry setting CPU affinity if we migrate. + * Losing affinity can be caused by CPU hotunplug/hotplug, or by + * cpuset(7). + */ +#if HAVE_SCHED_SETAFFINITY +static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue) +{ + cpu_set_t mask; + int ret; + + if (workqueue->cpu_affinity < 0) + return 0; + if (++workqueue->loop_count & SET_AFFINITY_CHECK_PERIOD_MASK) + return 0; + if (urcu_sched_getcpu() == workqueue->cpu_affinity) + return 0; + + CPU_ZERO(&mask); + CPU_SET(workqueue->cpu_affinity, &mask); +#if SCHED_SETAFFINITY_ARGS == 2 + ret = sched_setaffinity(0, &mask); +#else + ret = sched_setaffinity(0, sizeof(mask), &mask); +#endif + /* + * EINVAL is fine: can be caused by hotunplugged CPUs, or by + * cpuset(7). This is why we should always retry if we detect + * migration. + */ + if (ret && errno == EINVAL) { + ret = 0; + errno = 0; + } + return ret; +} +#else +static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue) +{ + return 0; +} +#endif + +static void futex_wait(int32_t *futex) +{ + /* Read condition before read futex */ + cmm_smp_mb(); + if (uatomic_read(futex) != -1) + return; + while (futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { + switch (errno) { + case EWOULDBLOCK: + /* Value already changed. */ + return; + case EINTR: + /* Retry if interrupted by signal. */ + break; /* Get out of switch. */ + default: + /* Unexpected error. */ + urcu_die(errno); + } + } +} + +static void futex_wake_up(int32_t *futex) +{ + /* Write to condition before reading/writing futex */ + cmm_smp_mb(); + if (caa_unlikely(uatomic_read(futex) == -1)) { + uatomic_set(futex, 0); + if (futex_async(futex, FUTEX_WAKE, 1, + NULL, NULL, 0) < 0) + urcu_die(errno); + } +} + +/* This is the code run by each worker thread. */ + +static void *workqueue_thread(void *arg) +{ + unsigned long cbcount; + struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg; + int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT); + + if (set_thread_cpu_affinity(workqueue)) + urcu_die(errno); + + if (workqueue->initialize_worker_fct) + workqueue->initialize_worker_fct(workqueue, workqueue->priv); + + if (!rt) { + uatomic_dec(&workqueue->futex); + /* Decrement futex before reading workqueue */ + cmm_smp_mb(); + } + for (;;) { + struct cds_wfcq_head cbs_tmp_head; + struct cds_wfcq_tail cbs_tmp_tail; + struct cds_wfcq_node *cbs, *cbs_tmp_n; + enum cds_wfcq_ret splice_ret; + + if (set_thread_cpu_affinity(workqueue)) + urcu_die(errno); + + if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) { + /* + * Pause requested. Become quiescent: remove + * ourself from all global lists, and don't + * process any callback. The callback lists may + * still be non-empty though. + */ + if (workqueue->worker_before_pause_fct) + workqueue->worker_before_pause_fct(workqueue, workqueue->priv); + cmm_smp_mb__before_uatomic_or(); + uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED); + while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0) + (void) poll(NULL, 0, 1); + uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED); + cmm_smp_mb__after_uatomic_and(); + if (workqueue->worker_after_resume_fct) + workqueue->worker_after_resume_fct(workqueue, workqueue->priv); + } + + cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); + splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, + &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->cbs_tail); + assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); + assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); + if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { + if (workqueue->grace_period_fct) + workqueue->grace_period_fct(workqueue, workqueue->priv); + cbcount = 0; + __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, + &cbs_tmp_tail, cbs, cbs_tmp_n) { + struct rcu_head *rhp; + + rhp = caa_container_of(cbs, + struct rcu_head, next); + rhp->func(rhp); + cbcount++; + } + uatomic_sub(&workqueue->qlen, cbcount); + } + if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP) + break; + if (workqueue->worker_before_wait_fct) + workqueue->worker_before_wait_fct(workqueue, workqueue->priv); + if (!rt) { + if (cds_wfcq_empty(&workqueue->cbs_head, + &workqueue->cbs_tail)) { + futex_wait(&workqueue->futex); + (void) poll(NULL, 0, 10); + uatomic_dec(&workqueue->futex); + /* + * Decrement futex before reading + * call_rcu list. + */ + cmm_smp_mb(); + } else { + (void) poll(NULL, 0, 10); + } + } else { + (void) poll(NULL, 0, 10); + } + if (workqueue->worker_after_wake_up_fct) + workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv); + } + if (!rt) { + /* + * Read call_rcu list before write futex. + */ + cmm_smp_mb(); + uatomic_set(&workqueue->futex, 0); + } + if (workqueue->finalize_worker_fct) + workqueue->finalize_worker_fct(workqueue, workqueue->priv); + return NULL; +} + +struct urcu_workqueue *urcu_workqueue_create(unsigned long flags, + int cpu_affinity, void *priv, + void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv)) +{ + struct urcu_workqueue *workqueue; + int ret; + + workqueue = malloc(sizeof(*workqueue)); + if (workqueue == NULL) + urcu_die(errno); + memset(workqueue, '\0', sizeof(*workqueue)); + cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail); + workqueue->qlen = 0; + workqueue->futex = 0; + workqueue->flags = flags; + workqueue->priv = priv; + workqueue->grace_period_fct = grace_period_fct; + workqueue->initialize_worker_fct = initialize_worker_fct; + workqueue->finalize_worker_fct = finalize_worker_fct; + workqueue->worker_before_wait_fct = worker_before_wait_fct; + workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct; + workqueue->worker_before_pause_fct = worker_before_pause_fct; + workqueue->worker_after_resume_fct = worker_after_resume_fct; + workqueue->cpu_affinity = cpu_affinity; + workqueue->loop_count = 0; + cmm_smp_mb(); /* Structure initialized before pointer is planted. */ + ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); + if (ret) { + urcu_die(ret); + } + return workqueue; +} + +static void wake_worker_thread(struct urcu_workqueue *workqueue) +{ + if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_CALL_RCU_RT)) + futex_wake_up(&workqueue->futex); +} + +static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue) +{ + int ret; + void *retval; + + uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP); + wake_worker_thread(workqueue); + + ret = pthread_join(workqueue->tid, &retval); + if (ret) { + urcu_die(ret); + } + if (retval != NULL) { + urcu_die(EINVAL); + } + workqueue->flags &= ~URCU_WORKQUEUE_STOP; + workqueue->tid = 0; + return 0; +} + +void urcu_workqueue_destroy(struct urcu_workqueue *workqueue) +{ + if (workqueue == NULL) { + return; + } + if (urcu_workqueue_destroy_worker(workqueue)) { + urcu_die(errno); + } + assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail)); + free(workqueue); +} + +void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue, + struct urcu_work *work, + void (*func)(struct urcu_work *work)) +{ + cds_wfcq_node_init(&work->next); + work->func = func; + cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next); + uatomic_inc(&workqueue->qlen); + wake_worker_thread(workqueue); +} + +static +void free_completion(struct urcu_ref *ref) +{ + struct urcu_workqueue_completion *completion; + + completion = caa_container_of(ref, struct urcu_workqueue_completion, ref); + free(completion); +} + +static +void _urcu_workqueue_wait_complete(struct urcu_work *work) +{ + struct urcu_workqueue_completion_work *completion_work; + struct urcu_workqueue_completion *completion; + + completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work); + completion = completion_work->completion; + if (!uatomic_sub_return(&completion->barrier_count, 1)) + futex_wake_up(&completion->futex); + urcu_ref_put(&completion->ref, free_completion); + free(completion_work); +} + +struct urcu_workqueue_completion *urcu_workqueue_create_completion(void) +{ + struct urcu_workqueue_completion *completion; + + completion = calloc(sizeof(*completion), 1); + if (!completion) + urcu_die(errno); + urcu_ref_set(&completion->ref, 1); + completion->barrier_count = 0; + return completion; +} + +void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion) +{ + urcu_ref_put(&completion->ref, free_completion); +} + +void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion) +{ + /* Wait for them */ + for (;;) { + uatomic_dec(&completion->futex); + /* Decrement futex before reading barrier_count */ + cmm_smp_mb(); + if (!uatomic_read(&completion->barrier_count)) + break; + futex_wait(&completion->futex); + } +} + +void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue, + struct urcu_workqueue_completion *completion) +{ + struct urcu_workqueue_completion_work *work; + + work = calloc(sizeof(*work), 1); + if (!work) + urcu_die(errno); + work->completion = completion; + urcu_ref_get(&completion->ref); + uatomic_inc(&completion->barrier_count); + urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete); +} + +/* + * Wait for all in-flight work to complete execution. + */ +void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue) +{ + struct urcu_workqueue_completion *completion; + + completion = urcu_workqueue_create_completion(); + if (!completion) + urcu_die(ENOMEM); + urcu_workqueue_queue_completion(workqueue, completion); + urcu_workqueue_wait_completion(completion); + urcu_workqueue_destroy_completion(completion); +} + +/* To be used in before fork handler. */ +void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue) +{ + uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE); + cmm_smp_mb__after_uatomic_or(); + wake_worker_thread(workqueue); + + while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0) + (void) poll(NULL, 0, 1); +} + +/* To be used in after fork parent handler. */ +void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue) +{ + uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE); + while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0) + (void) poll(NULL, 0, 1); +} + +void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue) +{ + int ret; + + /* Clear workqueue state from parent. */ + workqueue->flags &= ~URCU_WORKQUEUE_PAUSED; + workqueue->flags &= ~URCU_WORKQUEUE_PAUSE; + workqueue->tid = 0; + ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); + if (ret) { + urcu_die(ret); + } +} diff --git a/src/workqueue.h b/src/workqueue.h new file mode 100644 index 0000000..52b6973 --- /dev/null +++ b/src/workqueue.h @@ -0,0 +1,104 @@ +#ifndef _URCU_WORKQUEUE_H +#define _URCU_WORKQUEUE_H + +/* + * workqueue.h + * + * Userspace RCU header - Userspace workqueues + * + * Copyright (c) 2009,2017 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 + */ + +#include +#include + +#include + +#ifdef __cplusplus +extern "C" { +#endif + +/* Note that struct urcu_workqueue is opaque to callers. */ + +struct urcu_workqueue; +struct urcu_workqueue_completion; + +/* Flag values. */ + +#define URCU_WORKQUEUE_RT (1U << 0) +#define URCU_WORKQUEUE_STOP (1U << 1) +#define URCU_WORKQUEUE_PAUSE (1U << 2) +#define URCU_WORKQUEUE_PAUSED (1U << 3) + +/* + * The urcu_work data structure is placed in the structure to be acted + * upon via urcu_workqueue_queue_work(). + */ + +struct urcu_work { + struct cds_wfcq_node next; + void (*func)(struct urcu_work *head); +}; + +/* + * Exported functions + */ + +struct urcu_workqueue *urcu_workqueue_create(unsigned long flags, + int cpu_affinity, void *priv, + void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv), + void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv)); +void urcu_workqueue_destroy(struct urcu_workqueue *workqueue); + +/* + * Never fails. Should not be used to enqueue work from worker threads + * after the application invokes urcu_workqueue_free. + */ +void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue, + struct urcu_work *work, + void (*func)(struct urcu_work *work)); + +struct urcu_workqueue_completion *urcu_workqueue_create_completion(void); +void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion); + +void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue, + struct urcu_workqueue_completion *completion); +void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion); + +void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue); + +/* + * pause/resume/create worker threads. Can be used to pause worker + * threads across fork/clone while keeping the workqueue in place. + * Pause is used in parent pre-fork, resume in parent post-fork, create + * in child after-fork. + */ +void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue); +void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue); +void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue); + +#ifdef __cplusplus +} +#endif + +#endif /* _URCU_WORKQUEUE_H */