linux/lib/smp_processor_id.c
Steven Rostedt 5568b139f4 ftrace: debug smp_processor_id, use notrace preempt disable
The debug smp_processor_id caused a recursive fault in debugging
the irqsoff tracer. The tracer used a smp_processor_id in the
ftrace callback, and this function called preempt_disable which
also is traced. This caused a recursive fault (stack overload).

Since using smp_processor_id without debugging on does not cause
faults with the tracer (even when the tracer is wrong), the
debug version should not cause a system reboot.

This changes the debug_smp_processor_id to use the notrace versions
of preempt_disable and enable.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:39:17 +02:00

59 lines
1.1 KiB
C

/*
* 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();
cpumask_t this_mask;
if (likely(preempt_count))
goto out;
if (irqs_disabled())
goto out;
/*
* Kernel threads bound to a single CPU can safely use
* smp_processor_id():
*/
this_mask = cpumask_of_cpu(this_cpu);
if (cpus_equal(current->cpus_allowed, this_mask))
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);