File : s-musplo-leon.adb
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
4 -- --
5 -- S Y S T E M . M U L T I P R O C E S S O R S . S P I N _ L O C K S --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 2010-2015, AdaCore --
10 -- --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 ------------------------------------------------------------------------------
28
29 with System.Machine_Code;
30 with System.BB.Parameters;
31
32 package body System.Multiprocessors.Spin_Locks is
33
34 use System.Machine_Code;
35
36 ----------
37 -- Lock --
38 ----------
39
40 procedure Lock (Slock : in out Spin_Lock) is
41 Succeeded : Boolean;
42
43 begin
44 -- Loop until we can get the lock
45
46 loop
47 Try_Lock (Slock, Succeeded);
48 exit when Succeeded;
49 end loop;
50 end Lock;
51
52 ------------
53 -- Locked --
54 ------------
55
56 function Locked (Slock : Spin_Lock) return Boolean is
57 Lock_Value : Atomic_Flag;
58 Lock_Address : constant System.Address := Slock.Flag'Address;
59
60 begin
61
62 if System.BB.Parameters.Multiprocessor then
63
64 -- Only for multiprocessor
65
66 -- Read with "Alternate space" number 1 (Leon2/3 only) so we can skip
67 -- the data cache and work directly in RAM.
68
69 Asm ("lduba [%1] 1, %0" & ASCII.LF & ASCII.HT,
70 Outputs => Atomic_Flag'Asm_Output ("=r", Lock_Value),
71 Inputs => System.Address'Asm_Input ("r", Lock_Address),
72 Volatile => True,
73 Clobber => "memory");
74
75 return Lock_Value /= Unlocked;
76 else
77 return True;
78 end if;
79 end Locked;
80
81 --------------
82 -- Try_Lock --
83 --------------
84
85 procedure Try_Lock (Slock : in out Spin_Lock; Succeeded : out Boolean) is
86 Prev_Lock_Value : Atomic_Flag;
87 Lock_Address : constant System.Address := Slock.Flag'Address;
88
89 begin
90 if System.BB.Parameters.Multiprocessor then
91
92 -- Only for multiprocessor
93
94 -- Atomic test-and-set with "Alternate space" number 1 (Leon2/3 only)
95 -- so we can skip the data cache and work directly in RAM.
96
97 Asm ("ldstuba [%1] 1, %0" & ASCII.LF & ASCII.HT,
98 Outputs => Atomic_Flag'Asm_Output ("=r", Prev_Lock_Value),
99 Inputs => System.Address'Asm_Input ("r", Lock_Address),
100 Volatile => True,
101 Clobber => "memory");
102 Succeeded := (Prev_Lock_Value = Unlocked);
103 else
104 Succeeded := True;
105 end if;
106 end Try_Lock;
107
108 ------------
109 -- Unlock --
110 ------------
111
112 procedure Unlock (Slock : in out Spin_Lock) is
113 Lock_Address : constant System.Address := Slock.Flag'Address;
114
115 begin
116 if System.BB.Parameters.Multiprocessor then
117
118 -- Only for multiprocessor
119
120 -- Set lock value using "Alternate space" number 1 (Leon2/3 only) so
121 -- we can skip the data cache and directly write into RAM.
122
123 Asm ("stuba %%g0, [%0] 1" & ASCII.LF & ASCII.HT,
124 Inputs => System.Address'Asm_Input ("r", Lock_Address),
125 Volatile => True,
126 Clobber => "memory");
127 end if;
128 end Unlock;
129
130 end System.Multiprocessors.Spin_Locks;