On Mon, Feb 1, 2016 at 10:16 AM, Stas Sergeev <stsp@xxxxxxx> wrote: > 01.02.2016 21:04, Oleg Nesterov пишет: >> Yes, and SS_FORCE means "I know what I do", looks very simple. > But to me its not because I don't know what to do with > uc_stack after SS_FORCE is applied. > >> I won't argue, but to me it would be better to keep this EPERM if !force. >> Just because we should avoid the incompatible changes if possible. > > Ok then. Lets implement SS_FORCE. > What semantic should it have wrt uc_stack? > > sigaltstack(SS_DISABLE | SS_FORCE); > swapcontext(); > sigaltstack(set up new_sas); > rt_sigreturn(); > > What's at the end? Do we want a surprise for the user > that he's new_sas got ignored? More detail please. What context are you returning to with rt_sigreturn? What's in uc_stack? Presumably we should continue to honor uc_stack in rt_sigreturn. I'm less clear on whether we should have an implicit SS_FORCE when restoring uc_stack. I'm also not clear on why uc_stack exists in the first place. If I were designing this from scratch, I'd have signal delivery for an SA_ONSTACK signal save away the altstack information and clear it so that nested signals work without checking sp during signal delivery. But I'm not designing it from scratch, and I haven't spotted uc_stack or similar mentioned in POSIX or the man page, so I'm not really clear on what it's for. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
