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Kernel Hackers Manual 3.10
March 2020

kernel-plus-doc

Various documentation bits found in the kernel source

kernel-doc

Various bits of documentation found in the kernel sources.

kernel-rt-doc

Various documentation bits found in the kernel source

linux-manual-4.2

Linux kernel API manual pages for version 4.2

linux-manual-4.7

Linux kernel API manual pages for version 4.7

kernel-docs

Kernel Documentation

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, its 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

See the vsnprintf documentation for format string extensions over C99.

REFERENCED BY

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