Kernel coding no picnic, says Torvalds

Linux project lead Linus Torvalds has said it is not easy to become a major contributor to the Linux kernel.

Linus Torvalds
(Credit: Wikipedia)

In an email interview with ZDNet.com.au sister site ZDNet.co.uk last week, Torvalds said that, while it was relatively easy for coders and organisations to contribute small patches, the contribution of large patches, developed in isolation, could lead to both new and established contributors becoming frustrated.

"It's definitely not easy to become a 'big contributor'," wrote Torvalds. "For one thing, the kernel is quite complex and big, and it inevitably simply takes time to learn all the rules, not just for the code, but for how the whole development environment works. Similarly, for a new developer, it will take time before people start recognising the name and start trusting the developer to do the right things."

However, Torvalds argued that Linux kernel processes did make it easy to contribute small patches.

"[We] make it fairly easy for people to ease into kernel development," wrote Torvalds. "It seems to be working too. We literally have thousands of people with patches attributed to them in each release."

Torvalds wrote that nobody should expect to start sending "big and complex" patches early, as it takes time for new contributors and established coders to learn how to interact effectively.

"The worst thing anybody can do is to study the kernel alone and try to learn things in private, and then, however many months later, present all the established kernel developers with a big patch that just comes out of the blue," wrote Torvalds. "That's just going to be frustrating for everybody."

Torvalds advised new contributors to "start small" by sending "trivial patches".

"It may not sound exciting but, quite frankly, I don't think anybody who starts out believing that they want to rewrite some big piece of the kernel should even bother. Reality isn't that simple."

Torvalds admitted that frustrated developers might become alienated by the Linux development process, which he said could be improved.

"I don't think a 'perfect' process exists," wrote Torvalds. "Of course, some people will be alienated, and there's no doubt that the process could probably be improved."

The developer warned that Linux kernel development was "not a 'warm and fuzzy' environment where people sing Kumbaya around the fireplace" and that some "very opinionated people" were involved.

"The kernel is about pretty harsh technical issues, and mistakes are really frowned upon," wrote Torvalds. "In an OS kernel, there are simply more security and stability requirements, and the bar is really higher in some respects. That will inevitably also reflect in the response to patches."

Nonetheless, Torvalds said the patching process in Linux was more about human interaction than a quantifiable set of steps, such as those listed in official international standards processes.

Although thousands of developers are involved in Linux kernel coding, Torvalds argued that the development process was still efficient. "I think that one of the things we've been very good at is to scale up with a good network of maintainers, so that most people involved actually don't work closely with more than a handful of people," he wrote.

Mark Taylor, president of the Open Source Consortium, said that, in general, enterprise-class open source projects were designed to scale appropriately.

"The whole process scales very well," said Taylor. "Normally the people you find at the core [of open source projects] are professional software engineers; these guys know how to run software projects."

Torvalds' and Taylor's comments follow the publication of a guide to Linux kernel development by the Linux Foundation, which aims to prevent developers becoming frustrated with the process.