On Tue, May 05, 2020 at 11:54:05AM -0400, Tejun Heo wrote: > Hello, Bruce. > > On Mon, May 04, 2020 at 10:15:14PM -0400, J. Bruce Fields wrote: > > We're currently using it to pass the struct svc_rqst that a new nfsd > > thread needs. But once the new thread has gotten that, I guess it could > > set kthread->data to some global value that it uses to say "I'm a knfsd > > thread"? > > > > I suppose that would work. > > > > Though now I'm feeling greedy: it would be nice to have both some kind > > of global flag, *and* keep kthread->data pointing to svc_rqst (as that > > would give me a simpler and quicker way to figure out which client is > > conflicting). Could I take a flag bit in kthread->flags, maybe? > > Hmm... that'd be solvable if kthread->data can point to a struct which does > both things, right?
Isn't this some sort of chicken-and-egg problem? If you don't know whether a given kthread is an nfsd thread or not, then it's not safe to assume that kthread->data points to some nfsd-specific structure that might tell you whether it's an nfsd thread. > Because it doesn't have free() callback, it's a bit > awkward but the threadfn itself can unlink and RCU-free it before returning. It's only ever going to be referenced from the thread itself. This is just a way to ask "am I running as an nfsd thread?" when we're deep inside generic filesystem code somewhere. So I don't think there's any complicated lifetime issues here. --b.
