How to get dwarf stack trace of all live threads (HECs) on demand (e.g. SIGQUIT)?

Dear GHC devs, I recently encountered 100% ~ 400% CPU hogging situations to trouble-shoot, I managed to build and use a dwarf enabled GHC-8.10.3 on Ubuntu 18.04 and 20.04 for that, then I find it seemingly dumps only the main thread's stack trace when I press Ctrl+\, but my program is a concurrent language server that will fork a new thread to handle each LSP request, so I really need to see what is going on those threads when CPU get hogged, as the situation is not trivially reproducible, only occurs occasionally after some time of active IDE activity. And I can't figure out how to do that from the user guide, so help please! Thanks & best regards, Compl