X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=d33c731ad1e9eae6437ae95595ecf0c825f3e6e8;hp=c4a78752b5c383e4ade261c85051e18793bafa87;hb=074c3a1bde68f3d2607c5c4711ec456dbdb05bce;hpb=ffb4aaa79bfac71fbb57bf586d81af7097011f88

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index c4a7875..d33c731 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -45,6 +45,9 @@
 #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 {
@@ -62,6 +65,7 @@ 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)));
 
@@ -203,22 +207,42 @@ 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
@@ -232,9 +256,22 @@ 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)
@@ -243,8 +280,9 @@ 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);
 	}
 }
 
@@ -252,9 +290,22 @@ 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)
@@ -263,8 +314,9 @@ 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);
 	}
 }
 
@@ -275,10 +327,8 @@ 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);
 
 	/*
@@ -298,6 +348,9 @@ 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
@@ -309,7 +362,7 @@ 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();
@@ -341,7 +394,7 @@ 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
@@ -349,10 +402,10 @@ 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();
 	}
@@ -391,6 +444,7 @@ 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);
@@ -710,7 +764,7 @@ 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 */
@@ -880,7 +934,7 @@ 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);
 	}
 }
 
@@ -897,7 +951,7 @@ 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);
 }