Recent changes (master)

index 30c0d205..08c3d703 100644
@@ -1,6 +1,8 @@
 #ifndef ARCH_H
 #define ARCH_H
 
+#include <stdatomic.h>
+
 #include "../lib/types.h"
 
 enum {

@@ -34,6 +36,13 @@ extern unsigned long arch_flags;
 
 #define ARCH_CPU_CLOCK_WRAPS
 
+#define atomic_load_acquire(p)					\
+	atomic_load_explicit((_Atomic typeof(*(p)) *)(p),	\
+			     memory_order_acquire)
+#define atomic_store_release(p, v)				\
+	atomic_store_explicit((_Atomic typeof(*(p)) *)(p), (v),	\
+			      memory_order_release)
+
 /* IWYU pragma: begin_exports */
 #if defined(__i386__)
 #include "arch-x86.h"

index cab7ecaf..cd0810f4 100644
@@ -301,15 +301,13 @@ static int fio_ioring_cqring_reap(struct thread_data *td, unsigned int events,
 
 	head = *ring->head;
 	do {
-		read_barrier();
-		if (head == *ring->tail)
+		if (head == atomic_load_acquire(ring->tail))
 			break;
 		reaped++;
 		head++;
 	} while (reaped + events < max);
 
-	*ring->head = head;
-	write_barrier();
+	atomic_store_release(ring->head, head);
 	return reaped;
 }
 

@@ -384,15 +382,13 @@ static enum fio_q_status fio_ioring_queue(struct thread_data *td,
 
 	tail = *ring->tail;
 	next_tail = tail + 1;
-	read_barrier();
-	if (next_tail == *ring->head)
+	if (next_tail == atomic_load_acquire(ring->head))
 		return FIO_Q_BUSY;
 
 	if (o->cmdprio_percentage)
 		fio_ioring_prio_prep(td, io_u);
 	ring->array[tail & ld->sq_ring_mask] = io_u->index;
-	*ring->tail = next_tail;
-	write_barrier();
+	atomic_store_release(ring->tail, next_tail);
 
 	ld->queued++;
 	return FIO_Q_QUEUED;

index daa576da..398fdf91 100644
@@ -195,8 +195,8 @@ static int user_io_getevents(io_context_t aio_ctx, unsigned int max,
 		} else {
 			/* There is another completion to reap */
 			events[i] = ring->events[head];
-			read_barrier();
-			ring->head = (head + 1) % ring->nr;
+			atomic_store_release(&ring->head,
+					     (head + 1) % ring->nr);
 			i++;
 		}
 	}

index c34d8bf7..c7806acb 100644
@@ -169,7 +169,6 @@ void fio_sem_up(struct fio_sem *sem)
 	assert(sem->magic == FIO_SEM_MAGIC);
 
 	pthread_mutex_lock(&sem->lock);
-	read_barrier();
 	if (!sem->value && sem->waiters)
 		do_wake = 1;
 	sem->value++;

index 0a2cc6c4..953e4e67 100644
@@ -2,9 +2,10 @@
 #include <time.h>
 
 #include "fio.h"
+#include "lib/seqlock.h"
 #include "smalloc.h"
 
-struct timespec *fio_ts = NULL;
+struct fio_ts *fio_ts;
 int fio_gtod_offload = 0;
 static pthread_t gtod_thread;
 static os_cpu_mask_t fio_gtod_cpumask;

@@ -19,15 +20,17 @@ void fio_gtod_init(void)
 
 static void fio_gtod_update(void)
 {
-	if (fio_ts) {
-		struct timeval __tv;
-
-		gettimeofday(&__tv, NULL);
-		fio_ts->tv_sec = __tv.tv_sec;
-		write_barrier();
-		fio_ts->tv_nsec = __tv.tv_usec * 1000;
-		write_barrier();
-	}
+	struct timeval __tv;
+
+	if (!fio_ts)
+		return;
+
+	gettimeofday(&__tv, NULL);
+
+	write_seqlock_begin(&fio_ts->seqlock);
+	fio_ts->ts.tv_sec = __tv.tv_sec;
+	fio_ts->ts.tv_nsec = __tv.tv_usec * 1000;
+	write_seqlock_end(&fio_ts->seqlock);
 }
 
 struct gtod_cpu_data {

index f92ee8c4..c55f5cba 100644
@@ -4,6 +4,7 @@
 #include <sys/time.h>
 
 #include "arch/arch.h"
+#include "lib/seqlock.h"
 
 /*
  * Clock sources

@@ -22,20 +23,22 @@ extern int fio_start_gtod_thread(void);
 extern int fio_monotonic_clocktest(int debug);
 extern void fio_local_clock_init(void);
 
-extern struct timespec *fio_ts;
+extern struct fio_ts {
+	struct seqlock seqlock;
+	struct timespec ts;
+} *fio_ts;
 
 static inline int fio_gettime_offload(struct timespec *ts)
 {
-	time_t last_sec;
+	unsigned int seq;
 
 	if (!fio_ts)
 		return 0;
 
 	do {
-		read_barrier();
-		last_sec = ts->tv_sec = fio_ts->tv_sec;
-		ts->tv_nsec = fio_ts->tv_nsec;
-	} while (fio_ts->tv_sec != last_sec);
+		seq = read_seqlock_begin(&fio_ts->seqlock);
+		*ts = fio_ts->ts;
+	} while (read_seqlock_retry(&fio_ts->seqlock, seq));
 
 	return 1;
 }

index ae1438fd..7f50906b 100644
@@ -1934,8 +1934,8 @@ static void io_completed(struct thread_data *td, struct io_u **io_u_ptr,
 		if (io_u->error)
 			unlog_io_piece(td, io_u);
 		else {
-			io_u->ipo->flags &= ~IP_F_IN_FLIGHT;
-			write_barrier();
+			atomic_store_release(&io_u->ipo->flags,
+					io_u->ipo->flags & ~IP_F_IN_FLIGHT);
 		}
 	}
 

index 2ccc1b37..46c1c5e0 100644
@@ -6,7 +6,9 @@
 #include "types.h"
 
 #define FRAND32_MAX	(-1U)
+#define FRAND32_MAX_PLUS_ONE	(1.0 * (1ULL << 32))
 #define FRAND64_MAX	(-1ULL)
+#define FRAND64_MAX_PLUS_ONE	(1.0 * (1ULL << 32) * (1ULL << 32))
 
 struct taus88_state {
 	unsigned int s1, s2, s3;

@@ -106,11 +108,11 @@ static inline double __rand_0_1(struct frand_state *state)
 	if (state->use64) {
 		uint64_t val = __rand64(&state->state64);
 
-		return (val + 1.0) / (FRAND64_MAX + 1.0);
+		return (val + 1.0) / FRAND64_MAX_PLUS_ONE;
 	} else {
 		uint32_t val = __rand32(&state->state32);
 
-		return (val + 1.0) / (FRAND32_MAX + 1.0);
+		return (val + 1.0) / FRAND32_MAX_PLUS_ONE;
 	}
 }
 

@@ -122,7 +124,7 @@ static inline uint32_t rand32_upto(struct frand_state *state, uint32_t end)
 
 	r = __rand32(&state->state32);
 	end++;
-	return (int) ((double)end * (r / (FRAND32_MAX + 1.0)));
+	return (int) ((double)end * (r / FRAND32_MAX_PLUS_ONE));
 }
 
 static inline uint64_t rand64_upto(struct frand_state *state, uint64_t end)

@@ -133,7 +135,7 @@ static inline uint64_t rand64_upto(struct frand_state *state, uint64_t end)
 
 	r = __rand64(&state->state64);
 	end++;
-	return (uint64_t) ((double)end * (r / (FRAND64_MAX + 1.0)));
+	return (uint64_t) ((double)end * (r / FRAND64_MAX_PLUS_ONE));
 }
 
 /*

index 762b6ec1..afa9fd31 100644
@@ -18,13 +18,12 @@ static inline unsigned int read_seqlock_begin(struct seqlock *s)
 	unsigned int seq;
 
 	do {
-		seq = s->sequence;
+		seq = atomic_load_acquire(&s->sequence);
 		if (!(seq & 1))
 			break;
 		nop;
 	} while (1);
 
-	read_barrier();
 	return seq;
 }
 

@@ -36,14 +35,12 @@ static inline bool read_seqlock_retry(struct seqlock *s, unsigned int seq)
 
 static inline void write_seqlock_begin(struct seqlock *s)
 {
-	s->sequence++;
-	write_barrier();
+	s->sequence = atomic_load_acquire(&s->sequence) + 1;
 }
 
 static inline void write_seqlock_end(struct seqlock *s)
 {
-	write_barrier();
-	s->sequence++;
+	atomic_store_release(&s->sequence, s->sequence + 1);
 }
 
 #endif

index 8965cfbc..0c913368 100644
@@ -1,7 +1,7 @@
 #include <stdio.h>
 
 FILE *f_err;
-struct timespec *fio_ts = NULL;
+void *fio_ts;
 unsigned long fio_debug = 0;
 
 void __dprint(int type, const char *str, ...)

index b7fa6693..5ee0029d 100644
@@ -8,6 +8,7 @@
 #include <pthread.h>
 #include <libgen.h>
 
+#include "arch/arch.h"
 #include "fio.h"
 #include "verify.h"
 #include "trim.h"

@@ -1309,8 +1310,7 @@ int get_next_verify(struct thread_data *td, struct io_u *io_u)
 		/*
 		 * Ensure that the associated IO has completed
 		 */
-		read_barrier();
-		if (ipo->flags & IP_F_IN_FLIGHT)
+		if (atomic_load_acquire(&ipo->flags) & IP_F_IN_FLIGHT)
 			goto nothing;
 
 		rb_erase(n, &td->io_hist_tree);

@@ -1322,8 +1322,7 @@ int get_next_verify(struct thread_data *td, struct io_u *io_u)
 		/*
 		 * Ensure that the associated IO has completed
 		 */
-		read_barrier();
-		if (ipo->flags & IP_F_IN_FLIGHT)
+		if (atomic_load_acquire(&ipo->flags) & IP_F_IN_FLIGHT)
 			goto nothing;
 
 		flist_del(&ipo->list);