N parallel `open --profile <same>` (e.g. chatgpt-imagegen's web backend firing
3 image gens at once) collided on the profile-copy disk I/O and Chrome's profile
lock: every candidate burned its full ~30s launch timeout and ALL failed (0
success), because the loser instances hung without writing DevToolsActivePort.
ProfileLaunchLock takes a cross-process flock on a per-resolved-profile lock
file, held across the copy + launch until Chrome is up, so concurrent
same-profile launches queue instead of colliding — the storm becomes
all-succeed-serially instead of all-fail. The kernel releases the lock when the
holder exits, so a crash can't wedge the queue; acquisition is best-effort
(launch proceeds unlocked if it can't be taken). Uncontended single launches
are unaffected.
leeguooooo
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