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/module.h>
18 #include <linux/stringify.h>
19 #include <linux/smp.h>
20
21 /* waiting for a spinlock... */
22 #if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
23 #include <asm/hvcall.h>
24 #include <asm/iseries/hv_call.h>
25 #include <asm/smp.h>
26 #include <asm/firmware.h>
27
__spin_yield(raw_spinlock_t * lock)28 void __spin_yield(raw_spinlock_t *lock)
29 {
30 unsigned int lock_value, holder_cpu, yield_count;
31
32 lock_value = lock->slock;
33 if (lock_value == 0)
34 return;
35 holder_cpu = lock_value & 0xffff;
36 BUG_ON(holder_cpu >= NR_CPUS);
37 yield_count = lppaca[holder_cpu].yield_count;
38 if ((yield_count & 1) == 0)
39 return; /* virtual cpu is currently running */
40 rmb();
41 if (lock->slock != lock_value)
42 return; /* something has changed */
43 if (firmware_has_feature(FW_FEATURE_ISERIES))
44 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
45 ((u64)holder_cpu << 32) | yield_count);
46 #ifdef CONFIG_PPC_SPLPAR
47 else
48 plpar_hcall_norets(H_CONFER,
49 get_hard_smp_processor_id(holder_cpu), yield_count);
50 #endif
51 }
52
53 /*
54 * Waiting for a read lock or a write lock on a rwlock...
55 * This turns out to be the same for read and write locks, since
56 * we only know the holder if it is write-locked.
57 */
__rw_yield(raw_rwlock_t * rw)58 void __rw_yield(raw_rwlock_t *rw)
59 {
60 int lock_value;
61 unsigned int holder_cpu, yield_count;
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 yield_count = lppaca[holder_cpu].yield_count;
69 if ((yield_count & 1) == 0)
70 return; /* virtual cpu is currently running */
71 rmb();
72 if (rw->lock != lock_value)
73 return; /* something has changed */
74 if (firmware_has_feature(FW_FEATURE_ISERIES))
75 HvCall2(HvCallBaseYieldProcessor, HvCall_YieldToProc,
76 ((u64)holder_cpu << 32) | yield_count);
77 #ifdef CONFIG_PPC_SPLPAR
78 else
79 plpar_hcall_norets(H_CONFER,
80 get_hard_smp_processor_id(holder_cpu), yield_count);
81 #endif
82 }
83 #endif
84
__raw_spin_unlock_wait(raw_spinlock_t * lock)85 void __raw_spin_unlock_wait(raw_spinlock_t *lock)
86 {
87 while (lock->slock) {
88 HMT_low();
89 if (SHARED_PROCESSOR)
90 __spin_yield(lock);
91 }
92 HMT_medium();
93 }
94
95 EXPORT_SYMBOL(__raw_spin_unlock_wait);
96