X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=6495f465e1fade0477179be441694751cbc8c473;hp=04f7798c3f57a433a3756f267e0ffdc07e5e4552;hb=refs%2Fheads%2Fstable-0.7;hpb=254ebaf34ca0a7c18da1efbc561a1985d815b2d1

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index 04f7798..6495f46 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -43,6 +43,9 @@
 #include "urcu/tls-compat.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 {
@@ -52,6 +55,7 @@ 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)));
 
@@ -182,22 +186,42 @@ 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
@@ -211,9 +235,22 @@ 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)
@@ -222,8 +259,9 @@ 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);
 	}
 }
 
@@ -237,10 +275,8 @@ static void *call_rcu_thread(void *arg)
 	struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
 	struct rcu_head *rhp;
 	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);
 
 	/*
@@ -255,6 +291,9 @@ static void *call_rcu_thread(void *arg)
 		cmm_smp_mb();
 	}
 	for (;;) {
+		if (set_thread_cpu_affinity(crdp))
+			urcu_die(errno);
+
 		if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
 			/*
 			 * Pause requested. Become quiescent: remove
@@ -267,6 +306,8 @@ static void *call_rcu_thread(void *arg)
 			uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
 			while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
 				poll(NULL, 0, 1);
+			uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
+			cmm_smp_mb__after_uatomic_and();
 			rcu_register_thread();
 		}
 
@@ -350,6 +391,7 @@ 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);
@@ -620,12 +662,12 @@ void call_rcu(struct rcu_head *head,
 	cds_wfq_node_init(&head->next);
 	head->func = func;
 	/* Holding rcu read-side lock across use of per-cpu crdp */
-	rcu_read_lock();
+	_rcu_read_lock();
 	crdp = get_call_rcu_data();
 	cds_wfq_enqueue(&crdp->cbs, &head->next);
 	uatomic_inc(&crdp->qlen);
 	wake_call_rcu_thread(crdp);
-	rcu_read_unlock();
+	_rcu_read_unlock();
 }
 
 /*
@@ -763,6 +805,10 @@ void call_rcu_after_fork_parent(void)
 
 	cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
 		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);
+	}
 	call_rcu_unlock(&call_rcu_mutex);
 }