Al Viro <viro@xxxxxxxxxxxxxxxxxx> writes: > On Mon, Jun 21, 2021 at 01:54:56PM +0000, Al Viro wrote: >> On Tue, Jun 15, 2021 at 02:58:12PM -0700, Linus Torvalds wrote: >> >> > And I think our horrible "kernel threads return to user space when >> > done" is absolutely horrifically nasty. Maybe of the clever sort, but >> > mostly of the historical horror sort. >> >> How would you prefer to handle that, then? Separate magical path from >> kernel_execve() to switch to userland? We used to have something of >> that sort, and that had been a real horror... >> >> As it is, it's "kernel thread is spawned at the point similar to >> ret_from_fork(), runs the payload (which almost never returns) and >> then proceeds out to userland, same way fork(2) would've done." >> That way kernel_execve() doesn't have to do anything magical. >> >> Al, digging through the old notes and current call graph... > > FWIW, the major assumption back then had been that get_signal(), > signal_delivered() and all associated machinery (including coredumps) > runs *only* from SIGPENDING/NOTIFY_SIGNAL handling. > > And "has complete registers on stack" is only a part of that; > there was other fun stuff in the area ;-/ Do we want coredumps for > those, and if we do, will the de_thread stuff work there? Do we want coredumps from processes that use io_uring? yes Exactly what we want from io_uring threads is less clear. We can't really give much that is meaningful beyond the thread ids of the io_uring threads. What problems do are you seeing beyond the missing registers on the stack for kernel threads? I don't immediately see the connection between coredumps and de_thread. The function de_thread arranges for the fatal_signal_pending to be true, and that should work just fine for io_uring threads. The io_uring threads process the fatal_signal with get_signal and then proceed to exit eventually calling do_exit. Eric
