PRINTK(9)			 Driver Basics			     PRINTK(9)

NAME
       printk - print a kernel message

SYNOPSIS
       int printk(const char * fmt, ...);

ARGUMENTS
       fmt
	   format string

       ...
	   variable arguments

DESCRIPTION
       This is printk. It can be called from any context. We want it to work.

       We try to grab the console_lock. 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 console_unlock; and
       will send it to the consoles before releasing the lock.

       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.

SEE ALSO
       printf(3)

       See the vsnprintf documentation for format string extensions over C99.

COPYRIGHT
Kernel Hackers Manual 3.8.	   June 2014			     PRINTK(9)

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