smp_processor_id.c
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/*
* lib/smp_processor_id.c
*
* DEBUG_PREEMPT variant of smp_processor_id().
*/
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/sched.h>
notrace unsigned int debug_smp_processor_id(void)
{
unsigned long preempt_count = preempt_count();
int this_cpu = raw_smp_processor_id();
if (likely(preempt_count))
goto out;
if (irqs_disabled())
goto out;
/*
* Kernel threads bound to a single CPU can safely use
* smp_processor_id():
*/
if (cpumask_equal(tsk_cpus_allowed(current), cpumask_of(this_cpu)))
goto out;
/*
* It is valid to assume CPU-locality during early bootup:
*/
if (system_state != SYSTEM_RUNNING)
goto out;
/*
* Avoid recursion:
*/
preempt_disable_notrace();
if (!printk_ratelimit())
goto out_enable;
printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
"code: %s/%d\n",
preempt_count() - 1, current->comm, current->pid);
print_symbol("caller is %s\n", (long)__builtin_return_address(0));
dump_stack();
out_enable:
preempt_enable_no_resched_notrace();
out:
return this_cpu;
}
EXPORT_SYMBOL(debug_smp_processor_id);