关于trace_recursive_lock()的疑问。。。

chishanmingshen

from 3.7.0

1. 
   
2. /**
   
3. * ring_buffer_lock_reserve - reserve a part of the buffer
   
4. * @buffer: the ring buffer to reserve from
   
5. * @length: the length of the data to reserve (excluding event header)
   
6. *
   
7. * Returns a reseverd event on the ring buffer to copy directly to.
   
8. * The user of this interface will need to get the body to write into
   
9. * and can use the ring_buffer_event_data() interface.
   
10. *
    
11. * The length is the length of the data needed, not the event length
    
12. * which also includes the event header.
    
13. *
    
14. * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
    
15. * If NULL is returned, then nothing has been allocated or locked.
    
16. */
    
17. struct ring_buffer_event *
    
18. ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
    
19. {
    
20.         struct ring_buffer_per_cpu *cpu_buffer;
    
21.         struct ring_buffer_event *event;
    
22.         int cpu;
    
23. 
    
24.         if (ring_buffer_flags != RB_BUFFERS_ON)
    
25.                 return NULL;
    
26. 
    
27.         /* If we are tracing schedule, we don't want to recurse */<----注释说防止递归！
    
28.         preempt_disable_notrace();
    
29. 
    
30.         if (atomic_read(&buffer->record_disabled))
    
31.                 goto out_nocheck;
    
32. 
    
33.         if (trace_recursive_lock())<---------------------------递归计数，如何导致递归？
    
34.                 goto out_nocheck;
    
35. 
    
36.         cpu = raw_smp_processor_id();
    
37. 
    
38.         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    
39.                 goto out;
    
40. 
    
41.         cpu_buffer = buffer->buffers[cpu];
    
42. 
    
43.         if (atomic_read(&cpu_buffer->record_disabled))
    
44.                 goto out;
    
45. 
    
46.         if (length > BUF_MAX_DATA_SIZE)
    
47.                 goto out;
    
48. 
    
49.         event = rb_reserve_next_event(buffer, cpu_buffer, length);
    
50.         if (!event)
    
51.                 goto out;
    
52. 
    
53.         return event;
    
54. 
    
55. out:
    
56.         trace_recursive_unlock();
    
57. 
    
58. out_nocheck:
    
59.         preempt_enable_notrace();
    
60.         return NULL;
    
61. }
    

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哪种场景会递归调用此函数？求解！谢谢~~

chishanmingshen

求指点。。。

chishanmingshen

建议本版增加“调试”或“trace”子版！