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printk

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. Be aware of the fact that if oops_in_progress is not set, we might try to wake klogd up which could deadlock on runqueue lock if printk is called from scheduler code.

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.

SEE ALSO

printf(3)

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