[RFC,4/4] timers: poll-mode timers

diff --git a/platform/linux-generic/include/odp_config_internal.h b/platform/linux-generic/include/odp_config_internal.h
index b7ff610..eec9dac 100644
--- a/platform/linux-generic/include/odp_config_internal.h
+++ b/platform/linux-generic/include/odp_config_internal.h
@@ -118,6 +118,9 @@  extern "C" {
  */
 #define CONFIG_BURST_SIZE 16
 
+/* Value used to rate limit timer pool expiration processing. */
+#define ODP_CONFIG_TIMER_RUN_NSEC  (250)
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/platform/linux-generic/include/odp_time_internal.h b/platform/linux-generic/include/odp_time_internal.h
index 5a0bc75..1185f58 100644
--- a/platform/linux-generic/include/odp_time_internal.h
+++ b/platform/linux-generic/include/odp_time_internal.h
@@ -24,4 +24,6 @@  static inline uint64_t core_tick(void)
 #endif
 }
 
+uint64_t core_tick_diff_ns(uint64_t before, uint64_t after);
+
 #endif
diff --git a/platform/linux-generic/include/odp_timer_internal.h b/platform/linux-generic/include/odp_timer_internal.h
index b1cd73f..51959c0 100644
--- a/platform/linux-generic/include/odp_timer_internal.h
+++ b/platform/linux-generic/include/odp_timer_internal.h
@@ -39,4 +39,6 @@  typedef struct odp_timeout_hdr_stride {
 	uint8_t pad[ODP_CACHE_LINE_SIZE_ROUNDUP(sizeof(odp_timeout_hdr_t))];
 } odp_timeout_hdr_stride;
 
+int timer_run(void);
+
 #endif
diff --git a/platform/linux-generic/odp_schedule.c b/platform/linux-generic/odp_schedule.c
index 81e79c9..17cfaea 100644
--- a/platform/linux-generic/odp_schedule.c
+++ b/platform/linux-generic/odp_schedule.c
@@ -22,6 +22,8 @@ 
 #include <odp_align_internal.h>
 #include <odp_schedule_internal.h>
 #include <odp_schedule_ordered_internal.h>
+#include <odp_time_internal.h>
+#include <odp_timer_internal.h>
 #include <odp/api/sync.h>
 
 /* Number of priority levels  */
@@ -788,19 +790,28 @@  static int do_schedule(odp_queue_t *out_queue, odp_event_t out_ev[],
 	return 0;
 }
 
+static __thread uint64_t last_timer_run;
 
 static int schedule_loop(odp_queue_t *out_queue, uint64_t wait,
 			 odp_event_t out_ev[],
 			 unsigned int max_num)
 {
-	odp_time_t next, wtime;
-	int first = 1;
-	int ret;
+	uint64_t start, now;
+	int nr_events;
+
+	start = core_tick();
+
+	for (;;) {
+		now = core_tick();
+		if (ODP_CONFIG_TIMER_RUN_NSEC <=
+		    core_tick_diff_ns(last_timer_run, now)) {
+			last_timer_run = now;
+			(void)timer_run();
+		}
 
-	while (1) {
-		ret = do_schedule(out_queue, out_ev, max_num);
+		nr_events = do_schedule(out_queue, out_ev, max_num);
 
-		if (ret)
+		if (nr_events)
 			break;
 
 		if (wait == ODP_SCHED_WAIT)
@@ -809,18 +820,12 @@  static int schedule_loop(odp_queue_t *out_queue, uint64_t wait,
 		if (wait == ODP_SCHED_NO_WAIT)
 			break;
 
-		if (first) {
-			wtime = odp_time_local_from_ns(wait);
-			next = odp_time_sum(odp_time_local(), wtime);
-			first = 0;
-			continue;
-		}
-
-		if (odp_time_cmp(next, odp_time_local()) < 0)
+		now = core_tick();
+		if (core_tick_diff_ns(start, now) >= wait)
 			break;
 	}
 
-	return ret;
+	return nr_events;
 }
 
 static odp_event_t schedule(odp_queue_t *out_queue, uint64_t wait)
diff --git a/platform/linux-generic/odp_time.c b/platform/linux-generic/odp_time.c
index 81e0522..cd5c2a8 100644
--- a/platform/linux-generic/odp_time.c
+++ b/platform/linux-generic/odp_time.c
@@ -6,13 +6,65 @@ 
 
 #include <odp_posix_extensions.h>
 
-#include <time.h>
+#include <odp/api/cpu.h>
 #include <odp/api/time.h>
 #include <odp/api/hints.h>
 #include <odp_debug_internal.h>
+#include <odp_time_internal.h>
+
+#include <math.h>
+#include <time.h>
+#include <unistd.h>
+
+/* Number of nanoseconds per second. */
+#define ODP_NSEC_PER_SEC  (ODP_TIME_SEC_IN_NS)
+
+static uint64_t core_tick_hz;
 
 static odp_time_t start_time;
 
+uint64_t core_tick_diff_ns(uint64_t before, uint64_t after)
+{
+	uint64_t diff = after - before;
+
+	return llround(((double)diff / (double)core_tick_hz) *
+		       ODP_NSEC_PER_SEC);
+}
+
+static bool core_tick_init(void)
+{
+#if defined(__aarch64__)
+	uint64_t hz;
+	__asm__ volatile("mrs %0, cntfrq_el0" : "=r"(hz));
+	core_tick_hz = hz;
+	return true;
+#elif defined(__x86_64__)
+	uint32_t cpu_info[4];
+
+	/* Check for Invariant TSC. */
+	__asm__ volatile("cpuid" :
+			 "=a"(cpu_info[0]),
+			 "=b"(cpu_info[1]),
+			 "=c"(cpu_info[2]),
+			 "=d"(cpu_info[3]) :
+			 "a"(0x80000000));
+	if (cpu_info[0] >= 0x80000007) {
+		__asm__ volatile("cpuid" :
+				 "=a"(cpu_info[0]),
+				 "=b"(cpu_info[1]),
+				 "=c"(cpu_info[2]),
+				 "=d"(cpu_info[3]) :
+				 "a"(0x80000007));
+		if (!(cpu_info[3] & (1 << 8)))
+			return false;
+	}
+
+	core_tick_hz = odp_cpu_hz();
+	return true;
+#endif
+	return false;
+}
+
 static inline
 uint64_t time_to_ns(odp_time_t time)
 {
@@ -204,6 +256,9 @@  int odp_time_init_global(void)
 		start_time.tv_nsec = time.tv_nsec;
 	}
 
+	if (!core_tick_init())
+		ODP_ABORT("core_tick_init failed\n");
+
 	return ret;
 }
 
diff --git a/platform/linux-generic/odp_timer.c b/platform/linux-generic/odp_timer.c
index 6abb532..da569be 100644
--- a/platform/linux-generic/odp_timer.c
+++ b/platform/linux-generic/odp_timer.c
@@ -166,6 +166,7 @@  static inline void set_next_free(odp_timer *tim, uint32_t nf)
 
 typedef struct odp_timer_pool_s {
 /* Put frequently accessed fields in the first cache line */
+	uint64_t cur_ts;
 	odp_atomic_u64_t cur_tick;/* Current tick value */
 	uint64_t min_rel_tck;
 	uint64_t max_rel_tck;
@@ -179,11 +180,6 @@  typedef struct odp_timer_pool_s {
 	odp_timer_pool_param_t param;
 	char name[ODP_TIMER_POOL_NAME_LEN];
 	odp_shm_t shm;
-	timer_t timerid;
-	int notify_overrun;
-	pthread_t timer_thread; /* pthread_t of timer thread */
-	pid_t timer_thread_id; /* gettid() for timer thread */
-	int timer_thread_exit; /* request to exit for timer thread */
 } odp_timer_pool;
 
 #define MAX_TIMER_POOLS 255 /* Leave one for ODP_TIMER_INVALID */
@@ -219,10 +215,6 @@  static inline odp_timer_t tp_idx_to_handle(struct odp_timer_pool_s *tp,
 	return _odp_cast_scalar(odp_timer_t, (tp->tp_idx << INDEX_BITS) | idx);
 }
 
-/* Forward declarations */
-static void itimer_init(odp_timer_pool *tp);
-static void itimer_fini(odp_timer_pool *tp);
-
 static odp_timer_pool_t odp_timer_pool_new(const char *_name,
 					   const odp_timer_pool_param_t *param)
 {
@@ -245,6 +237,7 @@  static odp_timer_pool_t odp_timer_pool_new(const char *_name,
 		ODP_ABORT("%s: timer pool shm-alloc(%zuKB) failed\n",
 			  _name, (sz0 + sz1 + sz2) / 1024);
 	odp_timer_pool *tp = (odp_timer_pool *)odp_shm_addr(shm);
+	__atomic_store_n(&tp->cur_ts, core_tick(), __ATOMIC_RELAXED);
 	odp_atomic_init_u64(&tp->cur_tick, 0);
 	snprintf(tp->name, sizeof(tp->name), "%s", _name);
 	tp->shm = shm;
@@ -254,7 +247,6 @@  static odp_timer_pool_t odp_timer_pool_new(const char *_name,
 	tp->num_alloc = 0;
 	odp_atomic_init_u32(&tp->high_wm, 0);
 	tp->first_free = 0;
-	tp->notify_overrun = 1;
 	tp->tick_buf = (void *)((char *)odp_shm_addr(shm) + sz0);
 	tp->timers = (void *)((char *)odp_shm_addr(shm) + sz0 + sz1);
 	/* Initialize all odp_timer entries */
@@ -273,42 +265,14 @@  static odp_timer_pool_t odp_timer_pool_new(const char *_name,
 	tp->tp_idx = tp_idx;
 	odp_spinlock_init(&tp->lock);
 	timer_pool[tp_idx] = tp;
-	if (tp->param.clk_src == ODP_CLOCK_CPU)
-		itimer_init(tp);
 	return tp;
 }
 
-static void block_sigalarm(void)
-{
-	sigset_t sigset;
-
-	sigemptyset(&sigset);
-	sigaddset(&sigset, SIGALRM);
-	sigprocmask(SIG_BLOCK, &sigset, NULL);
-}
-
-static void stop_timer_thread(odp_timer_pool *tp)
-{
-	int ret;
-
-	ODP_DBG("stop\n");
-	tp->timer_thread_exit = 1;
-	ret = pthread_join(tp->timer_thread, NULL);
-	if (ret != 0)
-		ODP_ABORT("unable to join thread, err %d\n", ret);
-}
-
 static void odp_timer_pool_del(odp_timer_pool *tp)
 {
 	odp_spinlock_lock(&tp->lock);
 	timer_pool[tp->tp_idx] = NULL;
 
-	/* Stop timer triggering */
-	if (tp->param.clk_src == ODP_CLOCK_CPU)
-		itimer_fini(tp);
-
-	stop_timer_thread(tp);
-
 	if (tp->num_alloc != 0) {
 		/* It's a programming error to attempt to destroy a */
 		/* timer pool which is still in use */
@@ -673,121 +637,38 @@  static unsigned odp_timer_pool_expire(odp_timer_pool_t tpid, uint64_t tick)
 	return nexp;
 }
 
-/******************************************************************************
- * POSIX timer support
- * Functions that use Linux/POSIX per-process timers and related facilities
- *****************************************************************************/
-
-static void timer_notify(odp_timer_pool *tp)
+int timer_run(void)
 {
-	int overrun;
-	int64_t prev_tick;
-
-	if (tp->notify_overrun) {
-		overrun = timer_getoverrun(tp->timerid);
-		if (overrun) {
-			ODP_ERR("\n\t%d ticks overrun on timer pool \"%s\", timer resolution too high\n",
-				overrun, tp->name);
-			tp->notify_overrun = 0;
-		}
-	}
+	odp_timer_pool *tp;
+	size_t i;
+	int nexp = 0;
 
-	odp_timer *array = &tp->timers[0];
-	uint32_t i;
-	/* Prefetch initial cache lines (match 32 above) */
-	for (i = 0; i < 32; i += ODP_CACHE_LINE_SIZE / sizeof(array[0]))
-		__builtin_prefetch(&array[i], 0, 0);
-	prev_tick = odp_atomic_fetch_inc_u64(&tp->cur_tick);
+	for (i = 0; i < MAX_TIMER_POOLS; i++) {
+		tp = timer_pool[i];
 
-	/* Scan timer array, looking for timers to expire */
-	(void)odp_timer_pool_expire(tp, prev_tick + 1);
+		if (tp == NULL) break;
 
-	/* Else skip scan of timers. cur_tick was updated and next itimer
-	 * invocation will process older expiration ticks as well */
-}
-
-static void *timer_thread(void *arg)
-{
-	odp_timer_pool *tp = (odp_timer_pool *)arg;
-	sigset_t sigset;
-	int ret;
-	struct timespec tmo;
-	siginfo_t si;
-
-	tp->timer_thread_id = (pid_t)syscall(SYS_gettid);
+		/*
+		 * Check the last time this timer pool was expired. If one or
+		 * more periods have passed, attempt to expire it.
+		 */
+		uint64_t tp_ts =
+			__atomic_load_n(&tp->cur_ts, __ATOMIC_RELAXED);
+		uint64_t now = core_tick();
 
-	tmo.tv_sec = 0;
-	tmo.tv_nsec = ODP_TIME_MSEC_IN_NS * 100;
-
-	sigemptyset(&sigset);
-	/* unblock sigalarm in this thread */
-	sigprocmask(SIG_BLOCK, &sigset, NULL);
-
-	sigaddset(&sigset, SIGALRM);
-
-	while (1) {
-		ret = sigtimedwait(&sigset, &si, &tmo);
-		if (tp->timer_thread_exit) {
-			tp->timer_thread_id = 0;
-			return NULL;
+		if (core_tick_diff_ns(tp_ts, now) >= odp_timer_pool_res(tp)) {
+			if (__atomic_compare_exchange_n(
+				    &tp->cur_ts, &tp_ts, now, false,
+				    __ATOMIC_RELEASE, __ATOMIC_RELAXED)) {
+				uint64_t tp_tick;
+				tp_tick = odp_atomic_fetch_inc_u64(
+					&tp->cur_tick);
+				nexp += odp_timer_pool_expire(tp, tp_tick + 1);
+			}
 		}
-		if (ret > 0)
-			timer_notify(tp);
 	}
 
-	return NULL;
-}
-
-static void itimer_init(odp_timer_pool *tp)
-{
-	struct sigevent   sigev;
-	struct itimerspec ispec;
-	uint64_t res, sec, nsec;
-	int ret;
-
-	ODP_DBG("Creating POSIX timer for timer pool %s, period %"
-		PRIu64" ns\n", tp->name, tp->param.res_ns);
-
-	tp->timer_thread_id = 0;
-	ret = pthread_create(&tp->timer_thread, NULL, timer_thread, tp);
-	if (ret)
-		ODP_ABORT("unable to create timer thread\n");
-
-	/* wait thread set tp->timer_thread_id */
-	do {
-		sched_yield();
-	} while (tp->timer_thread_id == 0);
-
-	memset(&sigev, 0, sizeof(sigev));
-	sigev.sigev_notify          = SIGEV_THREAD_ID;
-	sigev.sigev_value.sival_ptr = tp;
-	sigev._sigev_un._tid = tp->timer_thread_id;
-	sigev.sigev_signo = SIGALRM;
-
-	if (timer_create(CLOCK_MONOTONIC, &sigev, &tp->timerid))
-		ODP_ABORT("timer_create() returned error %s\n",
-			  strerror(errno));
-
-	res  = tp->param.res_ns;
-	sec  = res / ODP_TIME_SEC_IN_NS;
-	nsec = res - sec * ODP_TIME_SEC_IN_NS;
-
-	memset(&ispec, 0, sizeof(ispec));
-	ispec.it_interval.tv_sec  = (time_t)sec;
-	ispec.it_interval.tv_nsec = (long)nsec;
-	ispec.it_value.tv_sec     = (time_t)sec;
-	ispec.it_value.tv_nsec    = (long)nsec;
-
-	if (timer_settime(tp->timerid, 0, &ispec, NULL))
-		ODP_ABORT("timer_settime() returned error %s\n",
-			  strerror(errno));
-}
-
-static void itimer_fini(odp_timer_pool *tp)
-{
-	if (timer_delete(tp->timerid) != 0)
-		ODP_ABORT("timer_delete() returned error %s\n",
-			  strerror(errno));
+	return nexp;
 }
 
 /******************************************************************************
@@ -1013,8 +894,6 @@  int odp_timer_init_global(void)
 #endif
 	odp_atomic_init_u32(&num_timer_pools, 0);
 
-	block_sigalarm();
-
 	return 0;
 }