arch/x86/kernel/tracepoint.c

   1 /*
   2  * Code for supporting irq vector tracepoints.
   3  *
   4  * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@hds.com>
   5  *
   6  */
   7 #include <asm/hw_irq.h>
   8 #include <asm/desc.h>
   9 #include <linux/atomic.h>
  10
  11 atomic_t trace_idt_ctr = ATOMIC_INIT(0);
  12 __aligned(PAGE_SIZE)
  13 struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
  14                                 (unsigned long) trace_idt_table };
  15
  16 /* No need to be aligned, but done to keep all IDTs defined the same way. */
  17 __aligned(PAGE_SIZE)
  18 gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;
  19
  20 static int trace_irq_vector_refcount;
  21 static DEFINE_MUTEX(irq_vector_mutex);
  22
  23 static void set_trace_idt_ctr(int val)
  24 {
  25         atomic_set(&trace_idt_ctr, val);
  26         /* Ensure the trace_idt_ctr is set before sending IPI */
  27         wmb();
  28 }
  29
  30 static void switch_idt(void *arg)
  31 {
  32         unsigned long flags;
  33
  34         local_irq_save(flags);
  35         load_current_idt();
  36         local_irq_restore(flags);
  37 }
  38
  39 void trace_irq_vector_regfunc(void)
  40 {
  41         mutex_lock(&irq_vector_mutex);
  42         if (!trace_irq_vector_refcount) {
  43                 set_trace_idt_ctr(1);
  44                 smp_call_function(switch_idt, NULL, 0);
  45                 switch_idt(NULL);
  46         }
  47         trace_irq_vector_refcount++;
  48         mutex_unlock(&irq_vector_mutex);
  49 }
  50
  51 void trace_irq_vector_unregfunc(void)
  52 {
  53         mutex_lock(&irq_vector_mutex);
  54         trace_irq_vector_refcount--;
  55         if (!trace_irq_vector_refcount) {
  56                 set_trace_idt_ctr(0);
  57                 smp_call_function(switch_idt, NULL, 0);
  58                 switch_idt(NULL);
  59         }
  60         mutex_unlock(&irq_vector_mutex);
  61 }