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 struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
  13                                 (unsigned long) trace_idt_table };
  14
  15 #ifndef CONFIG_X86_64
  16 gate_desc trace_idt_table[NR_VECTORS] __page_aligned_data
  17                                         = { { { { 0, 0 } } }, };
  18 #endif
  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         load_current_idt();
  33 }
  34
  35 void trace_irq_vector_regfunc(void)
  36 {
  37         mutex_lock(&irq_vector_mutex);
  38         if (!trace_irq_vector_refcount) {
  39                 set_trace_idt_ctr(1);
  40                 smp_call_function(switch_idt, NULL, 0);
  41                 switch_idt(NULL);
  42         }
  43         trace_irq_vector_refcount++;
  44         mutex_unlock(&irq_vector_mutex);
  45 }
  46
  47 void trace_irq_vector_unregfunc(void)
  48 {
  49         mutex_lock(&irq_vector_mutex);
  50         trace_irq_vector_refcount--;
  51         if (!trace_irq_vector_refcount) {
  52                 set_trace_idt_ctr(0);
  53                 smp_call_function(switch_idt, NULL, 0);
  54                 switch_idt(NULL);
  55         }
  56         mutex_unlock(&irq_vector_mutex);
  57 }