1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * lib/smp_processor_id.c
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * DEBUG_PREEMPT variant of smp_processor_id().
6*4882a593Smuzhiyun */
7*4882a593Smuzhiyun #include <linux/export.h>
8*4882a593Smuzhiyun #include <linux/kprobes.h>
9*4882a593Smuzhiyun #include <linux/sched.h>
10*4882a593Smuzhiyun
11*4882a593Smuzhiyun noinstr static
check_preemption_disabled(const char * what1,const char * what2)12*4882a593Smuzhiyun unsigned int check_preemption_disabled(const char *what1, const char *what2)
13*4882a593Smuzhiyun {
14*4882a593Smuzhiyun int this_cpu = raw_smp_processor_id();
15*4882a593Smuzhiyun
16*4882a593Smuzhiyun if (likely(preempt_count()))
17*4882a593Smuzhiyun goto out;
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun if (irqs_disabled())
20*4882a593Smuzhiyun goto out;
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun /*
23*4882a593Smuzhiyun * Kernel threads bound to a single CPU can safely use
24*4882a593Smuzhiyun * smp_processor_id():
25*4882a593Smuzhiyun */
26*4882a593Smuzhiyun if (current->nr_cpus_allowed == 1)
27*4882a593Smuzhiyun goto out;
28*4882a593Smuzhiyun
29*4882a593Smuzhiyun /*
30*4882a593Smuzhiyun * It is valid to assume CPU-locality during early bootup:
31*4882a593Smuzhiyun */
32*4882a593Smuzhiyun if (system_state < SYSTEM_SCHEDULING)
33*4882a593Smuzhiyun goto out;
34*4882a593Smuzhiyun
35*4882a593Smuzhiyun /*
36*4882a593Smuzhiyun * Avoid recursion:
37*4882a593Smuzhiyun */
38*4882a593Smuzhiyun preempt_disable_notrace();
39*4882a593Smuzhiyun
40*4882a593Smuzhiyun instrumentation_begin();
41*4882a593Smuzhiyun if (!printk_ratelimit())
42*4882a593Smuzhiyun goto out_enable;
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n",
45*4882a593Smuzhiyun what1, what2, preempt_count() - 1, current->comm, current->pid);
46*4882a593Smuzhiyun
47*4882a593Smuzhiyun printk("caller is %pS\n", __builtin_return_address(0));
48*4882a593Smuzhiyun dump_stack();
49*4882a593Smuzhiyun
50*4882a593Smuzhiyun out_enable:
51*4882a593Smuzhiyun instrumentation_end();
52*4882a593Smuzhiyun preempt_enable_no_resched_notrace();
53*4882a593Smuzhiyun out:
54*4882a593Smuzhiyun return this_cpu;
55*4882a593Smuzhiyun }
56*4882a593Smuzhiyun
debug_smp_processor_id(void)57*4882a593Smuzhiyun noinstr unsigned int debug_smp_processor_id(void)
58*4882a593Smuzhiyun {
59*4882a593Smuzhiyun return check_preemption_disabled("smp_processor_id", "");
60*4882a593Smuzhiyun }
61*4882a593Smuzhiyun EXPORT_SYMBOL(debug_smp_processor_id);
62*4882a593Smuzhiyun
__this_cpu_preempt_check(const char * op)63*4882a593Smuzhiyun noinstr void __this_cpu_preempt_check(const char *op)
64*4882a593Smuzhiyun {
65*4882a593Smuzhiyun check_preemption_disabled("__this_cpu_", op);
66*4882a593Smuzhiyun }
67*4882a593Smuzhiyun EXPORT_SYMBOL(__this_cpu_preempt_check);
68