Fix concurrency for mailbox and semaphores (#5222)

docs/CONTRIBUTORS

@@ -120,6 +120,7 @@ Krzysztof Boronski
 Krzysztof Boroński
 Kuba Ober
 Larry Doolittle
+Liam Braun
 Ludwig Rogiers
 Lukasz Dalek
 Maarten De Braekeleer

include/verilated_std.sv

@@ -40,7 +40,7 @@ package std;
 
       task put(T message);
 `ifdef VERILATOR_TIMING
-         if (m_bound != 0)
+         while (m_bound != 0 && m_queue.size() >= m_bound)
             wait (m_queue.size() < m_bound);
          m_queue.push_back(message);
 `endif
@@ -56,7 +56,9 @@ package std;
 
       task get(ref T message);
 `ifdef VERILATOR_TIMING
-         wait (m_queue.size() > 0);
+         while (m_queue.size() == 0) begin
+            wait (m_queue.size() > 0);
+         end
          message = m_queue.pop_front();
 `endif
       endtask
@@ -71,7 +73,9 @@ package std;
 
       task peek(ref T message);
 `ifdef VERILATOR_TIMING
-         wait (m_queue.size() > 0);
+         while (m_queue.size() == 0) begin
+            wait (m_queue.size() > 0);
+         end
          message = m_queue[0];
 `endif
       endtask
@@ -98,7 +102,9 @@ package std;
 
       task get(int keyCount = 1);
 `ifdef VERILATOR_TIMING
-         wait (m_keyCount >= keyCount);
+         while (m_keyCount < keyCount) begin
+            wait (m_keyCount >= keyCount);
+         end
          m_keyCount -= keyCount;
 `endif
       endtask

test_regress/t/t_dump_json.out

@@ -525,10 +525,10 @@
     {"type":"BASICDTYPE","name":"logic","addr":"(L)","loc":"c,33:32,33:33","dtypep":"(L)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
     {"type":"BASICDTYPE","name":"logic","addr":"(UE)","loc":"c,50:22,50:24","dtypep":"(UE)","keyword":"logic","generic":true,"rangep": []},
     {"type":"VOIDDTYPE","name":"","addr":"(HI)","loc":"c,51:21,51:30","dtypep":"(HI)","generic":false},
-    {"type":"BASICDTYPE","name":"logic","addr":"(QD)","loc":"c,119:22,119:23","dtypep":"(QD)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
+    {"type":"BASICDTYPE","name":"logic","addr":"(QD)","loc":"c,125:22,125:23","dtypep":"(QD)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
-    {"type":"BASICDTYPE","name":"logic","addr":"(JI)","loc":"c,121:22,121:23","dtypep":"(JI)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
+    {"type":"BASICDTYPE","name":"logic","addr":"(JI)","loc":"c,127:22,127:23","dtypep":"(JI)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
-    {"type":"BASICDTYPE","name":"logic","addr":"(KI)","loc":"c,156:17,156:56","dtypep":"(KI)","keyword":"logic","range":"295:0","generic":true,"rangep": []},
+    {"type":"BASICDTYPE","name":"logic","addr":"(KI)","loc":"c,162:17,162:56","dtypep":"(KI)","keyword":"logic","range":"295:0","generic":true,"rangep": []},
-    {"type":"BASICDTYPE","name":"string","addr":"(BG)","loc":"c,156:10,156:16","dtypep":"(BG)","keyword":"string","generic":true,"rangep": []},
+    {"type":"BASICDTYPE","name":"string","addr":"(BG)","loc":"c,162:10,162:16","dtypep":"(BG)","keyword":"string","generic":true,"rangep": []},
     {"type":"BASICDTYPE","name":"logic","addr":"(Q)","loc":"d,14:9,14:11","dtypep":"(Q)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
     {"type":"BASICDTYPE","name":"logic","addr":"(BB)","loc":"d,18:10,18:12","dtypep":"(BB)","keyword":"logic","range":"31:0","generic":true,"rangep": []},
     {"type":"BASICDTYPE","name":"logic","addr":"(MC)","loc":"d,33:26,33:31","dtypep":"(MC)","keyword":"logic","range":"31:0","generic":true,"rangep": []},

test_regress/t/t_mailbox_concurrent.out

@@ -0,0 +1,7 @@
+mailbox read 0
+mailbox read 1
+mailbox read 2
+mailbox write 3
+mailbox write 4
+mailbox write 5
+*-* All Finished *-*

test_regress/t/t_mailbox_concurrent.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Liam Braun and Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(simulator => 1);
+
+compile(
+    verilator_flags2 => ["--binary --timing"]
+    );
+
+execute(
+    check_finished => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_mailbox_concurrent.v

@@ -0,0 +1,49 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Liam Braun.
+// SPDX-License-Identifier: CC0-1.0
+
+module t();
+    mailbox #(int) m;
+
+    task automatic test_get;
+        int v;
+        m.get(v);
+        // Only one thread should be here at a time (mailbox empty)
+        $display("mailbox read %0t", $time);
+        #1;
+        m.put(v);
+    endtask
+
+    task automatic test_put;
+        int v;
+        m.put(42);
+        // Only one thread should be here at a time (mailbox full)
+        $display("mailbox write %0t", $time);
+        #1;
+        m.get(v);
+    endtask
+
+    initial begin
+        m = new(1);
+        m.put(42);
+
+        fork
+            test_get();
+            test_get();
+            test_get();
+        join
+
+        m = new(1);
+
+        fork
+            test_put();
+            test_put();
+            test_put();
+        join
+
+        $write("*-* All Finished *-*\n");
+        $finish;
+    end
+endmodule

test_regress/t/t_semaphore_concurrent.out

@@ -0,0 +1,5 @@
+0
+1
+2
+3
+*-* All Finished *-*

test_regress/t/t_semaphore_concurrent.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Liam Braun and Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(simulator => 1);
+
+compile(
+    verilator_flags2 => ["--binary --timing"]
+    );
+
+execute(
+    check_finished => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_semaphore_concurrent.v

@@ -0,0 +1,34 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Liam Braun.
+// SPDX-License-Identifier: CC0-1.0
+
+module t();
+    semaphore s;
+
+    // Stand-in for a task that should only be run by one thread at a time
+    task automatic exclusive_task;
+        $display("%0t", $time);
+        #1;
+    endtask
+
+    task automatic call_exclusive_task;
+        s.get(1);
+        exclusive_task();
+        s.put(1);
+    endtask
+
+    initial begin
+        s = new(1);
+        fork
+            call_exclusive_task();
+            call_exclusive_task();
+            call_exclusive_task();
+            call_exclusive_task();
+        join
+
+        $write("*-* All Finished *-*\n");
+        $finish;
+    end
+endmodule