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["majianpeng" <majianpeng@gmail.com>]

   Hi all:
         At present,I wanted to use blktrace.So I readed source and founded the problem.
         Following is my step:
         1:mount  -t debugfs debugfs /sys/kernel/debug
         2:blktrace -d /dev/sdb &
            $pid
         3:kill -9 $pid
         I found some file in /sys/kernel/debug/block.
         
	     If a btrace is ruing,but I call ioctl(BLKTRACETEARDOWN) 
		case BLKTRACETEARDOWN:
               ret = blk_trace_remove(q);
		int blk_trace_remove(struct request_queue *q)
 297 {               
 298         struct blk_trace *bt;
 299 
 300         bt = xchg(&q->blk_trace, NULL);
 301         if (!bt)
 302                 return -EINVAL;
 303                 
 304         if (bt->trace_state != Blktrace_running)
 305                 blk_trace_cleanup(bt);
 306                 
 307         return 0;
 308 }       
        But the btrace is in blktrace_running, so bt did not cleanup.
        When and Who cleanup btrace?
           
 				
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majianpeng
2011-06-29