1 /*
2 * Spin and read/write lock operations.
3 *
4 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
5 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
6 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
7 * Rework to support virtual processors
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
13 */
14
15 #include <linux/kernel.h>
16 #include <linux/spinlock.h>
17 #include <linux/export.h>
18 #include <linux/stringify.h>
19 #include <linux/smp.h>
20
21 /* waiting for a spinlock... */
22 #if defined(CONFIG_PPC_SPLPAR)
23 #include <asm/hvcall.h>
24 #include <asm/smp.h>
25
__spin_yield(arch_spinlock_t * lock)26 void __spin_yield(arch_spinlock_t *lock)
27 {
28 unsigned int lock_value, holder_cpu, yield_count;
29
30 lock_value = lock->slock;
31 if (lock_value == 0)
32 return;
33 holder_cpu = lock_value & 0xffff;
34 BUG_ON(holder_cpu >= NR_CPUS);
35 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
36 if ((yield_count & 1) == 0)
37 return; /* virtual cpu is currently running */
38 rmb();
39 if (lock->slock != lock_value)
40 return; /* something has changed */
41 plpar_hcall_norets(H_CONFER,
42 get_hard_smp_processor_id(holder_cpu), yield_count);
43 }
44 EXPORT_SYMBOL_GPL(__spin_yield);
45
46 /*
47 * Waiting for a read lock or a write lock on a rwlock...
48 * This turns out to be the same for read and write locks, since
49 * we only know the holder if it is write-locked.
50 */
__rw_yield(arch_rwlock_t * rw)51 void __rw_yield(arch_rwlock_t *rw)
52 {
53 int lock_value;
54 unsigned int holder_cpu, yield_count;
55
56 lock_value = rw->lock;
57 if (lock_value >= 0)
58 return; /* no write lock at present */
59 holder_cpu = lock_value & 0xffff;
60 BUG_ON(holder_cpu >= NR_CPUS);
61 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
62 if ((yield_count & 1) == 0)
63 return; /* virtual cpu is currently running */
64 rmb();
65 if (rw->lock != lock_value)
66 return; /* something has changed */
67 plpar_hcall_norets(H_CONFER,
68 get_hard_smp_processor_id(holder_cpu), yield_count);
69 }
70 #endif
71
arch_spin_unlock_wait(arch_spinlock_t * lock)72 void arch_spin_unlock_wait(arch_spinlock_t *lock)
73 {
74 smp_mb();
75
76 while (lock->slock) {
77 HMT_low();
78 if (SHARED_PROCESSOR)
79 __spin_yield(lock);
80 }
81 HMT_medium();
82
83 smp_mb();
84 }
85
86 EXPORT_SYMBOL(arch_spin_unlock_wait);
87