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 */
26 struct 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
preempt_disable(void)58 void 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
preempt_enable(void)71 void 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 }
80