1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Spin and read/write lock operations.
4 *
5 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
6 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
7 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
8 * Rework to support virtual processors
9 */
10
11 #include <linux/kernel.h>
12 #include <linux/spinlock.h>
13 #include <linux/export.h>
14 #include <linux/smp.h>
15
16 /* waiting for a spinlock... */
17 #if defined(CONFIG_PPC_SPLPAR)
18 #include <asm/hvcall.h>
19 #include <asm/smp.h>
20
21 void splpar_spin_yield(arch_spinlock_t *lock)
22 {
23 unsigned int lock_value, holder_cpu, yield_count;
24
25 lock_value = lock->slock;
26 if (lock_value == 0)
27 return;
28 holder_cpu = lock_value & 0xffff;
29 BUG_ON(holder_cpu >= NR_CPUS);
30
31 yield_count = yield_count_of(holder_cpu);
32 if ((yield_count & 1) == 0)
33 return; /* virtual cpu is currently running */
34 rmb();
35 if (lock->slock != lock_value)
36 return; /* something has changed */
37 yield_to_preempted(holder_cpu, yield_count);
38 }
39 EXPORT_SYMBOL_GPL(splpar_spin_yield);
40
41 /*
42 * Waiting for a read lock or a write lock on a rwlock...
43 * This turns out to be the same for read and write locks, since
44 * we only know the holder if it is write-locked.
45 */
46 void splpar_rw_yield(arch_rwlock_t *rw)
47 {
48 int lock_value;
49 unsigned int holder_cpu, yield_count;
50
51 lock_value = rw->lock;
52 if (lock_value >= 0)
53 return; /* no write lock at present */
54 holder_cpu = lock_value & 0xffff;
55 BUG_ON(holder_cpu >= NR_CPUS);
56
57 yield_count = yield_count_of(holder_cpu);
58 if ((yield_count & 1) == 0)
59 return; /* virtual cpu is currently running */
60 rmb();
61 if (rw->lock != lock_value)
62 return; /* something has changed */
63 yield_to_preempted(holder_cpu, yield_count);
64 }
65 #endif
66
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