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printk() - The Most Useful Tool is Now Showing its Age - Steven Rostedt, VMware & Sergey Senozhatsky

3,044 views · Published 24 October 2017 · 45:56 · Indexed 4 November 2026

Channel: The Linux Foundation · 2017 · Science & Technology

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printk() - The Most Useful Tool is Now Showing its Age - Steven Rostedt, VMware & Sergey Senozhatsky, Samsung Electronics

printk() has been the tool for debugging the Linux kernel and for being the display mechanism for Linux as long as Linux has been around. It's the first thing one sees as the life of the kernel begins, from the kernel banner and the last message at shutdown. It's critical as people take pictures of a kernel oops to send to the kernel developers to fix a bug, or to display on social media when that oops happens on the monitor on the back of an airplane seat in front of you.

But printk() is not a trivial utility. It serves many functionalities and some of them can be conflicting. Today with Linux running on machines with hundreds of CPUs, printk() can actually be the cause of live locks. This talk will discuss the history of printk, how it's grown, issues that have come about it, and why it is a pain that it is today.

About Steven Rostedt
Steven Rostedt currently works for VMware in their Open Source Technology Center. He's the maintainer of the stable releases for the Real Time patch (PREEMPT_RT). He is also one of the original developers for the Real Time patch. Steven is the main developer and maintainer for ftrace, the official tracer of the Linux kernel, as well as the user space tools trace-cmd and kernelshark. He also develops ktest.pl (in the kernel) and make localmodconfig.

About Sergey Senozhatsky
Sergey Senozhatsky currently works for Samsung Electronics, VD division, Korea.He is the co-maintainer of the printk() code. He is also a distinguished reviewer and developer for the upstream zsmalloc memory allocator and zram compressing block device driver.

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