关于printk

icymoon

2008.06.12.
  printk可以在任何上下文中调用。如果拿不到console_sem，就写入buffer后返回。推迟输出。推迟可能导致log level的变化。见代码注释。
/*
* This is printk.  It can be called from any context.  We want it to work.
*
* We try to grab the console_sem.  If we succeed, it's easy - we log the output and
* call the console drivers.  If we fail to get the semaphore we place the output
* into the log buffer and return.  The current holder of the console_sem will
* notice the new output in release_console_sem() and will send it to the
* consoles before releasing the semaphore.
*
* One effect of this deferred printing is that code which calls printk() and
* then changes console_loglevel may break. This is because console_loglevel
* is inspected when the actual printing occurs.
*/
               
               
               

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