On Sat, May 9, 2015 at 4:25 PM, Henrique de Moraes Holschuh <h...@hmh.eng.br> wrote: > On Sat, 09 May 2015, Alan Stern wrote: >> On Fri, 8 May 2015, Rafael J. Wysocki wrote: >> > My current view on that is that whether or not to do a sync() before >> > suspending >> > ultimately is a policy decision and should belong to user space as such >> > (modulo >> > the autosleep situation when user space may not know when the suspend is >> > going >> > to happen). >> > >> > Moreover, user space is free to do as many sync()s before suspending as it >> > wants to and the question here is whether or not the *kernel* should sync() >> > in the suspend code path. >> > >> > Since we pretty much can demonstrate that having just one sync() in there >> > is >> > not sufficient in general, should we put two of them in there? Or just >> > remove the existing one and leave it to user space entirely? >> >> I don't know about the advantages of one sync over two. But how about >> adding a "syncs_before_suspend" (or just "syncs") sysfs attribute that >> takes a small numeric value? The default can be 0, and the user could >> set it to 1 or 2 (or higher). > > IMO it would be much safer to both have that knob, and to set it to keep the > current behavior as the default. Userspace will adapt and change that knob > to whatever is sufficient based on what it does before signaling the kernel > to suspend. > > A regression in sync-before-suspend is sure to cause data loss episodes, > after all. And, as far as bikeshedding goes, IMHO syncs_before_suspend is > self-explanatory, which would be a very good reason to use it instead of the > shorter requires-you-to-know-what-it-is-about "syncs". >
When I first thought about this, I had a similar view: https://lkml.org/lkml/2014/1/23/45 But upon reflection, I do not believe that the kernel is adding value here, instead it is imposing a policy, and that policy decision is sometimes prohibitively expensive. User-space can do this for itself (and in the case of desktop distros, already does), and so the kernel should butt-out. thanks, Len Brown, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
