Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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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/config.h>
16#include <linux/kernel.h>
17#include <linux/spinlock.h>
18#include <linux/module.h>
19#include <linux/stringify.h>
20#include <asm/hvcall.h>
21#include <asm/iSeries/HvCall.h>
22
23/* waiting for a spinlock... */
24#if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
25
26void __spin_yield(spinlock_t *lock)
27{
28 unsigned int lock_value, holder_cpu, yield_count;
29 struct paca_struct *holder_paca;
30
31 lock_value = lock->lock;
32 if (lock_value == 0)
33 return;
34 holder_cpu = lock_value & 0xffff;
35 BUG_ON(holder_cpu >= NR_CPUS);
36 holder_paca = &paca[holder_cpu];
37 yield_count = holder_paca->lppaca.yield_count;
38 if ((yield_count & 1) == 0)
39 return; /* virtual cpu is currently running */
40 rmb();
41 if (lock->lock != lock_value)
42 return; /* something has changed */
43#ifdef CONFIG_PPC_ISERIES
44 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
45 ((u64)holder_cpu << 32) | yield_count);
46#else
47 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu),
48 yield_count);
49#endif
50}
51
52/*
53 * Waiting for a read lock or a write lock on a rwlock...
54 * This turns out to be the same for read and write locks, since
55 * we only know the holder if it is write-locked.
56 */
57void __rw_yield(rwlock_t *rw)
58{
59 int lock_value;
60 unsigned int holder_cpu, yield_count;
61 struct paca_struct *holder_paca;
62
63 lock_value = rw->lock;
64 if (lock_value >= 0)
65 return; /* no write lock at present */
66 holder_cpu = lock_value & 0xffff;
67 BUG_ON(holder_cpu >= NR_CPUS);
68 holder_paca = &paca[holder_cpu];
69 yield_count = holder_paca->lppaca.yield_count;
70 if ((yield_count & 1) == 0)
71 return; /* virtual cpu is currently running */
72 rmb();
73 if (rw->lock != lock_value)
74 return; /* something has changed */
75#ifdef CONFIG_PPC_ISERIES
76 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
77 ((u64)holder_cpu << 32) | yield_count);
78#else
79 plpar_hcall_norets(H_CONFER, get_hard_smp_processor_id(holder_cpu),
80 yield_count);
81#endif
82}
83#endif
84
85void spin_unlock_wait(spinlock_t *lock)
86{
87 while (lock->lock) {
88 HMT_low();
89 if (SHARED_PROCESSOR)
90 __spin_yield(lock);
91 }
92 HMT_medium();
93}
94
95EXPORT_SYMBOL(spin_unlock_wait);