Version: 54.0.2824.0 (Official Build) dev (64-bit) - Linux
Version: 54.0.2830.1 (Official Build) canary SyzyASan (32-bit) - Windows

Updated Chrome to the above versions yesterday. Today, both the browser process and individual renderers on both machines are locking up for 10-20 seconds at a time, randomly.

(1) On the Linux machine the first lockup was immediately on the first run after a reboot, for about 10 seconds. The first thing I did was remove an extension that was hidden in the hamburger menu, by opening the hamburger menu and right-clicking on it and hitting "Remove". The browser process locked up for over a minute after the menu closed, before the "Are you sure?" dialog opened.

(2) Since then, individual tabs have frozen, usually while scrolling with the mouse wheel, at random times but never for as long. Also when this happens, I tend to try to open a new tab with the tab bar button, and often (but not always) find that the browser process is frozen too. I haven't noticed if the browser process freezes while no tabs are frozen.

The Windows machine shows behaviour (2) as well, and it started a few minutes before I rebooted the Linux machine.

Both machines are syncing the same profile.

Possibly unrelated: on the Windows machine, a Google-internal extension started crashing every few minutes this morning as well. (It's since backed off to crashing only occasionally - before today it was rock-solid.) The same extension hasn't had any problems on the Linux machine.