1// SPDX-License-Identifier: GPL-2.0
 2#include <config.h>
 3
 4#include "preempt.h"
 5
 6#include "assume.h"
 7#include "locks.h"
 8
 9/* Support NR_CPUS of at most 64 */
10#define CPU_PREEMPTION_LOCKS_INIT0 LOCK_IMPL_INITIALIZER
11#define CPU_PREEMPTION_LOCKS_INIT1 \
12	CPU_PREEMPTION_LOCKS_INIT0, CPU_PREEMPTION_LOCKS_INIT0
13#define CPU_PREEMPTION_LOCKS_INIT2 \
14	CPU_PREEMPTION_LOCKS_INIT1, CPU_PREEMPTION_LOCKS_INIT1
15#define CPU_PREEMPTION_LOCKS_INIT3 \
16	CPU_PREEMPTION_LOCKS_INIT2, CPU_PREEMPTION_LOCKS_INIT2
17#define CPU_PREEMPTION_LOCKS_INIT4 \
18	CPU_PREEMPTION_LOCKS_INIT3, CPU_PREEMPTION_LOCKS_INIT3
19#define CPU_PREEMPTION_LOCKS_INIT5 \
20	CPU_PREEMPTION_LOCKS_INIT4, CPU_PREEMPTION_LOCKS_INIT4
21
22/*
23 * Simulate disabling preemption by locking a particular cpu. NR_CPUS
24 * should be the actual number of cpus, not just the maximum.
25 */
26struct lock_impl cpu_preemption_locks[NR_CPUS] = {
27	CPU_PREEMPTION_LOCKS_INIT0
28#if (NR_CPUS - 1) & 1
29	, CPU_PREEMPTION_LOCKS_INIT0
30#endif
31#if (NR_CPUS - 1) & 2
32	, CPU_PREEMPTION_LOCKS_INIT1
33#endif
34#if (NR_CPUS - 1) & 4
35	, CPU_PREEMPTION_LOCKS_INIT2
36#endif
37#if (NR_CPUS - 1) & 8
38	, CPU_PREEMPTION_LOCKS_INIT3
39#endif
40#if (NR_CPUS - 1) & 16
41	, CPU_PREEMPTION_LOCKS_INIT4
42#endif
43#if (NR_CPUS - 1) & 32
44	, CPU_PREEMPTION_LOCKS_INIT5
45#endif
46};
47
48#undef CPU_PREEMPTION_LOCKS_INIT0
49#undef CPU_PREEMPTION_LOCKS_INIT1
50#undef CPU_PREEMPTION_LOCKS_INIT2
51#undef CPU_PREEMPTION_LOCKS_INIT3
52#undef CPU_PREEMPTION_LOCKS_INIT4
53#undef CPU_PREEMPTION_LOCKS_INIT5
54
55__thread int thread_cpu_id;
56__thread int preempt_disable_count;
57
58void preempt_disable(void)
59{
60	BUG_ON(preempt_disable_count < 0 || preempt_disable_count == INT_MAX);
61
62	if (preempt_disable_count++)
63		return;
64
65	thread_cpu_id = nondet_int();
66	assume(thread_cpu_id >= 0);
67	assume(thread_cpu_id < NR_CPUS);
68	lock_impl_lock(&cpu_preemption_locks[thread_cpu_id]);
69}
70
71void preempt_enable(void)
72{
73	BUG_ON(preempt_disable_count < 1);
74
75	if (--preempt_disable_count)
76		return;
77
78	lock_impl_unlock(&cpu_preemption_locks[thread_cpu_id]);
79}