Signals on Luther Monson

The Bugs Were Our Own Linker Wraps: Making a PHP Timeout Actually Time Out

Wed, 16 Sep 2026 19:35:00 -0700

In the stack guard post the villain was a -Wl,--wrap linker flag that turned off PHP’s C-stack overflow guard. It wasn’t the only one. Until August, max_execution_time did nothing in ePHPm on Linux, for the same reason. We had wrapped the function that arms it to a no-op. A runaway script ran until the HTTP layer’s request timeout gave up on it and sent a 504. The PHP thread kept burning CPU after that.

We Disabled PHP's Stack Guard Ourselves: Containing Segfaults in a Single-Process PHP Server

Sun, 06 Sep 2026 15:05:00 -0700

php-fpm has a property nobody thinks about until they leave it. When a worker segfaults, you lose one request. The master forks a new child and life goes on. ePHPm runs every tenant’s PHP as threads inside one process. That’s where the memory and latency wins come from. It also means one tenant’s segfault takes down every other tenant on the box.

This is the story of closing that gap in four steps over about two weeks. The last step turned out to be a bug we’d put there ourselves. It’s also the payoff for the thread pool work in the previous post. Everything below that actually shipped depends on ePHPm owning its own PHP threads.

PHP Signal Safety - The Init Ordering Bug Nobody Warns You About

Sun, 12 Apr 2026 20:15:00 -0700

Last week I wrote about why ePHPm embeds PHP from Rust and promised the signal bug its own post. Here it is. It’s the kind of bug where the fix is about ten lines and the explanation is the whole post. Nothing in PHP’s embed documentation (there’s barely any) tells you that initializing PHP has process-wide side effects. Those side effects assume PHP is the only thing in the process.

The setup

The first working version of ephpm serve looked like every async Rust program. It was #[tokio::main]-style. Build the runtime, then inside it load config, initialize PHP and start the HTTP server. PHP requests run on spawn_blocking threads. Simplified: