From d07319f790eb38c867bd04a23de674e2393825ff Mon Sep 17 00:00:00 2001
From: Rickard Green <rickard@erlang.org>
Date: Sun, 22 Mar 2015 20:20:28 +0100
Subject: Better support for poor os monotonic sources

---
 .../sys/common/erl_os_monotonic_time_extender.c    | 88 ++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 erts/emulator/sys/common/erl_os_monotonic_time_extender.c

(limited to 'erts/emulator/sys/common/erl_os_monotonic_time_extender.c')

diff --git a/erts/emulator/sys/common/erl_os_monotonic_time_extender.c b/erts/emulator/sys/common/erl_os_monotonic_time_extender.c
new file mode 100644
index 0000000000..f3633b7267
--- /dev/null
+++ b/erts/emulator/sys/common/erl_os_monotonic_time_extender.c
@@ -0,0 +1,88 @@
+/*
+ * %CopyrightBegin%
+ * 
+ * Copyright Ericsson AB 2015. All Rights Reserved.
+ * 
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ * 
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ * 
+ * %CopyrightEnd%
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+#include "erl_os_monotonic_time_extender.h"
+
+#ifdef USE_THREADS
+
+static void *os_monotonic_time_extender(void *vstatep)
+{
+    ErtsOsMonotonicTimeExtendState *state = (ErtsOsMonotonicTimeExtendState *) vstatep;
+    long sleep_time = state->check_interval*1000;
+    Uint32 (*raw_os_mtime)(void) = state->raw_os_monotonic_time;
+    Uint32 last_msb = 0;
+
+    while (1) {
+	Uint32 msb = (*raw_os_mtime)() & (((Uint32) 1) << 31);
+
+	if (msb != last_msb) {
+	    int ix = ((int) (last_msb >> 31)) & 1;
+	    Uint32 xtnd = (Uint32) erts_atomic32_read_nob(&state->extend[ix]);
+	    erts_atomic32_set_nob(&state->extend[ix], (erts_aint32_t) (xtnd + 1));
+	    last_msb = msb;
+	}
+	erts_milli_sleep(sleep_time);
+    }
+
+    erl_exit(ERTS_ABORT_EXIT, "os_monotonic_time_extender thread terminating");
+    return NULL;
+}
+
+static erts_tid_t os_monotonic_extender_tid;
+#endif
+
+void
+erts_init_os_monotonic_time_extender(ErtsOsMonotonicTimeExtendState *statep,
+				     Uint32 (*raw_os_monotonic_time)(void),
+				     int check_seconds)
+{
+#ifdef USE_THREADS
+    statep->raw_os_monotonic_time = raw_os_monotonic_time;
+    erts_atomic32_init_nob(&statep->extend[0], (erts_aint32_t) 0);
+    erts_atomic32_init_nob(&statep->extend[1], (erts_aint32_t) 0);
+    statep->check_interval = check_seconds;
+
+#else
+    statep->extend[0] = (Uint32) 0;
+    statep->extend[1] = (Uint32) 0;
+    statep->last_msb = (ErtsMonotonicTime) 0;
+#endif
+}
+
+void
+erts_late_init_os_monotonic_time_extender(ErtsOsMonotonicTimeExtendState *statep)
+{
+#ifdef USE_THREADS
+    erts_thr_opts_t thr_opts = ERTS_THR_OPTS_DEFAULT_INITER;
+    thr_opts.detached = 1;
+    thr_opts.suggested_stack_size = 4;
+
+#if 0
+    thr_opts.name = "os_monotonic_time_extender";
+#endif
+
+    erts_thr_create(&os_monotonic_extender_tid,
+		    os_monotonic_time_extender,
+		    (void*) statep,
+		    &thr_opts);
+#endif
+}
-- 
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