5568b139f4
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>
58 lines
1.1 KiB
C
58 lines
1.1 KiB
C
/*
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* lib/smp_processor_id.c
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*
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* DEBUG_PREEMPT variant of smp_processor_id().
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*/
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#include <linux/module.h>
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#include <linux/kallsyms.h>
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#include <linux/sched.h>
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notrace unsigned int debug_smp_processor_id(void)
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{
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unsigned long preempt_count = preempt_count();
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int this_cpu = raw_smp_processor_id();
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cpumask_t this_mask;
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if (likely(preempt_count))
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goto out;
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if (irqs_disabled())
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goto out;
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/*
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* Kernel threads bound to a single CPU can safely use
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* smp_processor_id():
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*/
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this_mask = cpumask_of_cpu(this_cpu);
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if (cpus_equal(current->cpus_allowed, this_mask))
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goto out;
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/*
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* It is valid to assume CPU-locality during early bootup:
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*/
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if (system_state != SYSTEM_RUNNING)
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goto out;
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/*
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* Avoid recursion:
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*/
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preempt_disable_notrace();
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if (!printk_ratelimit())
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goto out_enable;
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printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
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"code: %s/%d\n",
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preempt_count() - 1, current->comm, current->pid);
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print_symbol("caller is %s\n", (long)__builtin_return_address(0));
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dump_stack();
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out_enable:
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preempt_enable_no_resched_notrace();
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out:
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return this_cpu;
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}
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EXPORT_SYMBOL(debug_smp_processor_id);
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