blob: 0c9c8d7d07345cd2f5def8c2801b466c8330a48b [file] [log] [blame]
Paul Mackerras40ef8cb2005-10-10 22:50:37 +10001/*
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
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100015#include <linux/kernel.h>
16#include <linux/spinlock.h>
Paul Gortmaker4b16f8e2011-07-22 18:24:23 -040017#include <linux/export.h>
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100018#include <linux/stringify.h>
Paul Mackerras734d6522005-10-31 13:57:01 +110019#include <linux/smp.h>
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100020
21/* waiting for a spinlock... */
Stephen Rothwellf5339272012-03-15 18:18:00 +000022#if defined(CONFIG_PPC_SPLPAR)
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100023#include <asm/hvcall.h>
Paul Mackerras2249ca92005-11-07 13:18:13 +110024#include <asm/smp.h>
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100025
Thomas Gleixner445c8952009-12-02 19:49:50 +010026void __spin_yield(arch_spinlock_t *lock)
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100027{
28 unsigned int lock_value, holder_cpu, yield_count;
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100029
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);
Anton Blanchard7ffcf8e2013-08-07 02:01:46 +100035 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100036 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 */
Stephen Rothwellf5339272012-03-15 18:18:00 +000041 plpar_hcall_norets(H_CONFER,
42 get_hard_smp_processor_id(holder_cpu), yield_count);
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100043}
44
45/*
46 * Waiting for a read lock or a write lock on a rwlock...
47 * This turns out to be the same for read and write locks, since
48 * we only know the holder if it is write-locked.
49 */
Thomas Gleixnerfb3a6bb2009-12-03 20:01:19 +010050void __rw_yield(arch_rwlock_t *rw)
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100051{
52 int lock_value;
53 unsigned int holder_cpu, yield_count;
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100054
55 lock_value = rw->lock;
56 if (lock_value >= 0)
57 return; /* no write lock at present */
58 holder_cpu = lock_value & 0xffff;
59 BUG_ON(holder_cpu >= NR_CPUS);
Anton Blanchard7ffcf8e2013-08-07 02:01:46 +100060 yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100061 if ((yield_count & 1) == 0)
62 return; /* virtual cpu is currently running */
63 rmb();
64 if (rw->lock != lock_value)
65 return; /* something has changed */
Stephen Rothwellf5339272012-03-15 18:18:00 +000066 plpar_hcall_norets(H_CONFER,
67 get_hard_smp_processor_id(holder_cpu), yield_count);
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100068}
69#endif
70
Thomas Gleixner0199c4e2009-12-02 20:01:25 +010071void arch_spin_unlock_wait(arch_spinlock_t *lock)
Paul Mackerras40ef8cb2005-10-10 22:50:37 +100072{
73 while (lock->slock) {
74 HMT_low();
75 if (SHARED_PROCESSOR)
76 __spin_yield(lock);
77 }
78 HMT_medium();
79}
80
Thomas Gleixner0199c4e2009-12-02 20:01:25 +010081EXPORT_SYMBOL(arch_spin_unlock_wait);