On 3/28/23 5:32?AM, Michael Ellerman wrote: > Jens Axboe <ax...@kernel.dk> writes: >> Powerpc sets up PF_KTHREAD and PF_IO_WORKER with a NULL pt_regs, which >> from my (arguably very short) checking is not commonly done for other >> archs. This is fine, except when PF_IO_WORKER's have been created and >> the task does something that causes a coredump to be generated. > > Do kthread's ever core dump? I didn't think they did, but I can't find > any logic to prevent it.
kthreads aren't associated with the original task, they just exist by themselves. They also can't take signals. Eg they cannot core dump, just oops :-) This is different than io workers that do show up as threads, but they still don't exit to userspace. That is why it ended being a problem. > As Nick said we should probably have a non-NULL regs for PF_IO_WORKERS, > but I'll still take this as a nice backportable fix for the immediate > crash. > > I tagged it as Fixes: pointing back at the commit that added ppr_get(), > even though I don't know for sure the bug was triggerable back then > (v4.8). Thanks! -- Jens Axboe