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d4697bc9 | 1 | /* Copyright (C) 2011-2014 Free Software Foundation, Inc. |
63d143a2 CM |
2 | This file is part of the GNU C Library. |
3 | Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
ab84e3ff PE |
16 | License along with the GNU C Library. If not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
63d143a2 CM |
18 | |
19 | #include "pthreadP.h" | |
20 | #include <arch/spr_def.h> | |
21 | #include <atomic.h> | |
22 | ||
23 | /* Bound point for bounded exponential backoff */ | |
24 | #define BACKOFF_MAX 2048 | |
25 | ||
26 | /* Initial cycle delay for exponential backoff */ | |
27 | #define BACKOFF_START 32 | |
28 | ||
29 | #ifdef __tilegx__ | |
30 | /* Use cmpexch() after the initial fast-path exch to avoid | |
31 | invalidating the cache line of the lock holder. */ | |
32 | # define TNS(p) atomic_exchange_acq((p), 1) | |
33 | # define CMPTNS(p) atomic_compare_and_exchange_val_acq((p), 1, 0) | |
34 | #else | |
35 | # define TNS(p) __insn_tns(p) | |
36 | # define CMPTNS(p) __insn_tns(p) | |
37 | # define SPR_CYCLE SPR_CYCLE_LOW /* The low 32 bits are sufficient. */ | |
38 | #endif | |
39 | ||
40 | int | |
41 | pthread_spin_lock (pthread_spinlock_t *lock) | |
42 | { | |
43 | if (__builtin_expect (TNS (lock) != 0, 0)) | |
44 | { | |
45 | unsigned int backoff = BACKOFF_START; | |
46 | while (CMPTNS (lock) != 0) | |
47 | { | |
48 | unsigned int start = __insn_mfspr (SPR_CYCLE); | |
49 | while (__insn_mfspr (SPR_CYCLE) - start < backoff) | |
50 | ; | |
51 | if (backoff < BACKOFF_MAX) | |
52 | backoff *= 2; | |
53 | } | |
54 | } | |
55 | return 0; | |
56 | } |