On Fri, May 1, 2015 at 9:14 AM, Rik van Riel <[email protected]> wrote: > On 05/01/2015 12:05 PM, Andy Lutomirski wrote: >> On Fri, May 1, 2015 at 9:00 AM, Rik van Riel <[email protected]> wrote: > >>> I suspect we probably only need two possible function >>> calls at syscall exit time: >>> >>> 1) A function that is called with interrupts still >>> enabled, testing flags that could be set again >>> if something happens (eg. preemption) between >>> when the function is called, and we return to >>> user space. >>> >>> 2) A function that is called after the point of >>> no return, with interrupts disabled, which >>> does (mostly) small things that only happen >>> once. >> >> I think we only need one function. It would be (asm pseudocode): >> >> disable irqs; >> if (slow) { >> save extra regs; >> call function; >> restore extra regs; >> } >> >> return via opportunistic sysret path. >> >> I can't see any legitimate reason for the current mess, except that >> it's no complicated and so poorly documented that everyone's afraid of >> fixing it. > > do_notify_resume() can call do_signal(), which can sleep, after > which all bets are off on what new flags may have been set. > > On the other hand, we have stuff that can run just fine with > irqs disabled that we really want to call only once. > > For that reason, I suspect we need two functions.
C can have loops just as easily as assembly can :) I still don't see why we need magic asm code to schedule and deliver signals. We certainly need to have valid pt_regs to deliver signals, but that's easy and much cheaper than it used to be. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
