A nice blog post from Ahrefs about the Skylake and Kaby Lake CPU bug recently patched by Intel, which disproportionately affected OCaml.
For reference, see this message from the Debian mailing list.
[WARNING] Intel Skylake/Kaby Lake processors: broken hyper-threading
TL;DR: unfixed Skylake and Kaby Lake processors could, in some
situations, dangerously misbehave when hyper-threading is enabled.
Disable hyper-threading immediately in BIOS/UEFI to work around the
problem. Read this advisory for instructions about an Intel-provided
On 2017-05-29, Mark Shinwell, a core OCaml toolchain developer,
contacted the Debian developer responsible for the intel-microcode
package with key information about a Intel processor issue that could be
easily triggered by the OCaml compiler.
For people on Linux, there is a perl script for checking whether your CPU is likely affected.
For an idea of how likely this bug is to occur, we had four reports recently in Lwt alone from users that had been running stress tests, where the stack traces happened to imply Lwt might be the problem.