On Wed, Jul 27, 2016 at 12:42 AM, Rafael J. Wysocki <[email protected]> wrote: > On Tuesday, July 26, 2016 04:53:19 PM Josh Poimboeuf wrote: >> On Tue, Jul 26, 2016 at 10:15:39PM +0200, Rafael J. Wysocki wrote: >> > On Tuesday, July 26, 2016 09:39:05 AM Josh Poimboeuf wrote: >> > > On Tue, Jul 26, 2016 at 01:32:28PM +0200, Rafael J. Wysocki wrote: >> > > > Hi, >> > > > >> > > > The following commit: >> > > > >> > > > commit 13523309495cdbd57a0d344c0d5d574987af007f >> > > > Author: Josh Poimboeuf <[email protected]> >> > > > Date: Thu Jan 21 16:49:21 2016 -0600 >> > > > >> > > > x86/asm/acpi: Create a stack frame in do_suspend_lowlevel() >> > > > >> > > > do_suspend_lowlevel() is a callable non-leaf function which doesn't >> > > > honor CONFIG_FRAME_POINTER, which can result in bad stack traces. >> > > > >> > > > Create a stack frame for it when CONFIG_FRAME_POINTER is enabled. >> > > > >> > > > is reported to cause a resume-from-hibernation regression due to an >> > > > attempt >> > > > to execute an NX page (we've seen quite a bit of that recently). >> > > > >> > > > I'm asking the reporter to try 4.7, but if the problem is still there, >> > > > we'll >> > > > need to revert the above I'm afraid. >> > >> > So the bug is still there in 4.7 and it goes away after reverting the above >> > commit. I guess I'll send a revert then. >> >> Hm, the code in wakeup_64.S seems quite magical, but I can't figure out >> why this change causes a panic. Is it really causing the panic or is it >> uncovering some other bug? > > It doesn't matter really. > > It surely interacts with something in a really odd way, but that only means > that its impact goes far beyond what was expected when it was applied. Its > changelog is inadequate as a result and so on. > >> Maybe we should hold off on reverting until we understand the issue. > > Which very well may take forever. > > And AFAICS this is a fix for a theoretical issue and it *reliably* triggers a > very practical kernel panic for this particular reporter. I'd rather live > with the theoretical issue unfixed to be honest.
Well, actually, the best part is that do_suspend_lowlevel() is not even called during hibernation or resume from it. It only is called during suspend-to-RAM. Question now is how the change made by the commit in question can affect hibernation which is an unrelated code path. We know for a fact that it does affect it, but how? Thanks, Rafael
