On Tue, Oct 18, 2016 at 2:40 PM, Joshua Liebow-Feeser <he...@joshlf.com> wrote:
> > > On Tue, Oct 18, 2016 at 2:16 PM, Ian Lance Taylor <i...@golang.org> wrote: > >> On Tue, Oct 18, 2016 at 12:30 PM, Joshua Liebow-Feeser <he...@joshlf.com> >> wrote: >> > >> > I'm playing around with implementing a wait-free channel in the runtime >> > package, and as part of this, it'd be really nice to have double-word >> > compare-and-swap (CAS). Barring that, however, for my purposes, it would >> > actually be fine to have a one-word value that encodes both a pointer >> and >> > some extra information using bit packing. The problem, though, is that >> if I >> > store this value as, for example, a uintptr, the GC may not realize that >> > it's a pointer. So my question is: are there any bits in a pointer >> which, >> > when modified, won't mess with the GC? Note that since this is >> implemented >> > in the runtime, I'm totally OK with relying on behavior specific to the >> > current GC implementation. >> >> See runtime/lfstack*.go. >> > Awesome, thanks! > Actually, quick follow-up. I noticed that the lfstack implementation side-steps the GC issue by just not keeping pointers. That might work for me if I just store runtime.g pointers, but that raises another question: can the GC ever free g's, or are they just explicitly freed when a goroutine quits? That is, is it safe for me to store a pointer/counter hybrid like in lfstack - where that pointer is a *g - and assume that the GC won't collect the g from out from under me? > >> Ian >> > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
