X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=65f63ee51670ae73b9c8ead9869554e4f8f35a82;hp=c2e175b7524982ab341f73865248404e8e303542;hb=1a186a881c195c0f240c0baa813056b0cc1eab91;hpb=fc236e5edb83c2273e251be4cd659f47491cc90c

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index c2e175b..65f63ee 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -36,14 +36,19 @@
 #include <sched.h>
 
 #include "config.h"
+#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"
 
+#define SET_AFFINITY_CHECK_PERIOD		(1U << 8)	/* 256 */
+#define SET_AFFINITY_CHECK_PERIOD_MASK		(SET_AFFINITY_CHECK_PERIOD - 1)
+
 /* Data structure that identifies a call_rcu thread. */
 
 struct call_rcu_data {
@@ -61,12 +66,14 @@ struct call_rcu_data {
 	unsigned long qlen; /* maintained for debugging. */
 	pthread_t tid;
 	int cpu_affinity;
+	unsigned long gp_count;
 	struct cds_list_head list;
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
 struct call_rcu_completion {
 	int barrier_count;
 	int32_t futex;
+	struct urcu_ref ref;
 };
 
 struct call_rcu_completion_work {
@@ -100,23 +107,7 @@ static struct call_rcu_data *default_call_rcu_data;
  * CPUs rather than only to specific threads.
  */
 
-#ifdef HAVE_SCHED_GETCPU
-
-static int urcu_sched_getcpu(void)
-{
-	return sched_getcpu();
-}
-
-#else /* #ifdef HAVE_SCHED_GETCPU */
-
-static int urcu_sched_getcpu(void)
-{
-	return -1;
-}
-
-#endif /* #else #ifdef HAVE_SCHED_GETCPU */
-
-#if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU)
+#if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
 
 /*
  * Pointer to array of pointers to per-CPU call_rcu_data structures
@@ -201,22 +192,42 @@ static void call_rcu_unlock(pthread_mutex_t *pmp)
 		urcu_die(ret);
 }
 
+/*
+ * 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 call_rcu_data *crdp)
 {
 	cpu_set_t mask;
+	int ret;
 
 	if (crdp->cpu_affinity < 0)
 		return 0;
+	if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK)
+		return 0;
+	if (urcu_sched_getcpu() == crdp->cpu_affinity)
+		return 0;
 
 	CPU_ZERO(&mask);
 	CPU_SET(crdp->cpu_affinity, &mask);
 #if SCHED_SETAFFINITY_ARGS == 2
-	return sched_setaffinity(0, &mask);
+	ret = sched_setaffinity(0, &mask);
 #else
-	return sched_setaffinity(0, sizeof(mask), &mask);
+	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
@@ -230,9 +241,22 @@ static void call_rcu_wait(struct call_rcu_data *crdp)
 {
 	/* Read call_rcu list before read futex */
 	cmm_smp_mb();
-	if (uatomic_read(&crdp->futex) == -1)
-		futex_async(&crdp->futex, FUTEX_WAIT, -1,
-		      NULL, NULL, 0);
+	if (uatomic_read(&crdp->futex) != -1)
+		return;
+	while (futex_async(&crdp->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 call_rcu_wake_up(struct call_rcu_data *crdp)
@@ -241,8 +265,9 @@ static void call_rcu_wake_up(struct call_rcu_data *crdp)
 	cmm_smp_mb();
 	if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
 		uatomic_set(&crdp->futex, 0);
-		futex_async(&crdp->futex, FUTEX_WAKE, 1,
-		      NULL, NULL, 0);
+		if (futex_async(&crdp->futex, FUTEX_WAKE, 1,
+				NULL, NULL, 0) < 0)
+			urcu_die(errno);
 	}
 }
 
@@ -250,9 +275,22 @@ static void call_rcu_completion_wait(struct call_rcu_completion *completion)
 {
 	/* Read completion barrier count before read futex */
 	cmm_smp_mb();
-	if (uatomic_read(&completion->futex) == -1)
-		futex_async(&completion->futex, FUTEX_WAIT, -1,
-		      NULL, NULL, 0);
+	if (uatomic_read(&completion->futex) != -1)
+		return;
+	while (futex_async(&completion->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 call_rcu_completion_wake_up(struct call_rcu_completion *completion)
@@ -261,8 +299,9 @@ static void call_rcu_completion_wake_up(struct call_rcu_completion *completion)
 	cmm_smp_mb();
 	if (caa_unlikely(uatomic_read(&completion->futex) == -1)) {
 		uatomic_set(&completion->futex, 0);
-		futex_async(&completion->futex, FUTEX_WAKE, 1,
-		      NULL, NULL, 0);
+		if (futex_async(&completion->futex, FUTEX_WAKE, 1,
+				NULL, NULL, 0) < 0)
+			urcu_die(errno);
 	}
 }
 
@@ -273,10 +312,8 @@ static void *call_rcu_thread(void *arg)
 	unsigned long cbcount;
 	struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
 	int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
-	int ret;
 
-	ret = set_thread_cpu_affinity(crdp);
-	if (ret)
+	if (set_thread_cpu_affinity(crdp))
 		urcu_die(errno);
 
 	/*
@@ -296,6 +333,9 @@ static void *call_rcu_thread(void *arg)
 		struct cds_wfcq_node *cbs, *cbs_tmp_n;
 		enum cds_wfcq_ret splice_ret;
 
+		if (set_thread_cpu_affinity(crdp))
+			urcu_die(errno);
+
 		if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
 			/*
 			 * Pause requested. Become quiescent: remove
@@ -307,7 +347,7 @@ static void *call_rcu_thread(void *arg)
 			cmm_smp_mb__before_uatomic_or();
 			uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
 			while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
-				poll(NULL, 0, 1);
+				(void) poll(NULL, 0, 1);
 			uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
 			cmm_smp_mb__after_uatomic_and();
 			rcu_register_thread();
@@ -339,7 +379,7 @@ static void *call_rcu_thread(void *arg)
 			if (cds_wfcq_empty(&crdp->cbs_head,
 					&crdp->cbs_tail)) {
 				call_rcu_wait(crdp);
-				poll(NULL, 0, 10);
+				(void) poll(NULL, 0, 10);
 				uatomic_dec(&crdp->futex);
 				/*
 				 * Decrement futex before reading
@@ -347,10 +387,10 @@ static void *call_rcu_thread(void *arg)
 				 */
 				cmm_smp_mb();
 			} else {
-				poll(NULL, 0, 10);
+				(void) poll(NULL, 0, 10);
 			}
 		} else {
-			poll(NULL, 0, 10);
+			(void) poll(NULL, 0, 10);
 		}
 		rcu_thread_online();
 	}
@@ -389,6 +429,7 @@ static void call_rcu_data_init(struct call_rcu_data **crdpp,
 	crdp->flags = flags;
 	cds_list_add(&crdp->list, &call_rcu_data_list);
 	crdp->cpu_affinity = cpu_affinity;
+	crdp->gp_count = 0;
 	cmm_smp_mb();  /* Structure initialized before pointer is planted. */
 	*crdpp = crdp;
 	ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
@@ -667,10 +708,10 @@ void call_rcu(struct rcu_head *head,
 	struct call_rcu_data *crdp;
 
 	/* Holding rcu read-side lock across use of per-cpu crdp */
-	rcu_read_lock();
+	_rcu_read_lock();
 	crdp = get_call_rcu_data();
 	_call_rcu(head, func, crdp);
-	rcu_read_unlock();
+	_rcu_read_unlock();
 }
 
 /*
@@ -708,7 +749,7 @@ void call_rcu_data_free(struct call_rcu_data *crdp)
 		uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
 		wake_call_rcu_thread(crdp);
 		while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
-			poll(NULL, 0, 1);
+			(void) poll(NULL, 0, 1);
 	}
 	if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
 		/* Create default call rcu data if need be */
@@ -768,6 +809,15 @@ void free_all_cpu_call_rcu_data(void)
 	free(crdp);
 }
 
+static
+void free_completion(struct urcu_ref *ref)
+{
+	struct call_rcu_completion *completion;
+
+	completion = caa_container_of(ref, struct call_rcu_completion, ref);
+	free(completion);
+}
+
 static
 void _rcu_barrier_complete(struct rcu_head *head)
 {
@@ -776,8 +826,9 @@ void _rcu_barrier_complete(struct rcu_head *head)
 
 	work = caa_container_of(head, struct call_rcu_completion_work, head);
 	completion = work->completion;
-	uatomic_dec(&completion->barrier_count);
-	call_rcu_completion_wake_up(completion);
+	if (!uatomic_sub_return(&completion->barrier_count, 1))
+		call_rcu_completion_wake_up(completion);
+	urcu_ref_put(&completion->ref, free_completion);
 	free(work);
 }
 
@@ -787,19 +838,19 @@ void _rcu_barrier_complete(struct rcu_head *head)
 void rcu_barrier(void)
 {
 	struct call_rcu_data *crdp;
-	struct call_rcu_completion completion;
+	struct call_rcu_completion *completion;
 	int count = 0;
 	int was_online;
 
 	/* Put in offline state in QSBR. */
-	was_online = rcu_read_ongoing();
+	was_online = _rcu_read_ongoing();
 	if (was_online)
 		rcu_thread_offline();
 	/*
 	 * Calling a rcu_barrier() within a RCU read-side critical
 	 * section is an error.
 	 */
-	if (rcu_read_ongoing()) {
+	if (_rcu_read_ongoing()) {
 		static int warned = 0;
 
 		if (!warned) {
@@ -809,11 +860,17 @@ void rcu_barrier(void)
 		goto online;
 	}
 
+	completion = calloc(sizeof(*completion), 1);
+	if (!completion)
+		urcu_die(errno);
+
 	call_rcu_lock(&call_rcu_mutex);
 	cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
 		count++;
 
-	completion.barrier_count = count;
+	/* Referenced by rcu_barrier() and each call_rcu thread. */
+	urcu_ref_set(&completion->ref, count + 1);
+	completion->barrier_count = count;
 
 	cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
 		struct call_rcu_completion_work *work;
@@ -821,20 +878,23 @@ void rcu_barrier(void)
 		work = calloc(sizeof(*work), 1);
 		if (!work)
 			urcu_die(errno);
-		work->completion = &completion;
+		work->completion = completion;
 		_call_rcu(&work->head, _rcu_barrier_complete, crdp);
 	}
 	call_rcu_unlock(&call_rcu_mutex);
 
 	/* Wait for them */
 	for (;;) {
-		uatomic_dec(&completion.futex);
+		uatomic_dec(&completion->futex);
 		/* Decrement futex before reading barrier_count */
 		cmm_smp_mb();
-		if (!uatomic_read(&completion.barrier_count))
+		if (!uatomic_read(&completion->barrier_count))
 			break;
-		call_rcu_completion_wait(&completion);
+		call_rcu_completion_wait(completion);
 	}
+
+	urcu_ref_put(&completion->ref, free_completion);
+
 online:
 	if (was_online)
 		rcu_thread_online();
@@ -859,7 +919,7 @@ void call_rcu_before_fork(void)
 	}
 	cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
 		while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
-			poll(NULL, 0, 1);
+			(void) poll(NULL, 0, 1);
 	}
 }
 
@@ -876,7 +936,7 @@ void call_rcu_after_fork_parent(void)
 		uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
 	cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
 		while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0)
-			poll(NULL, 0, 1);
+			(void) poll(NULL, 0, 1);
 	}
 	call_rcu_unlock(&call_rcu_mutex);
 }