On Monday, 23 July 2007 23:55, Nigel Cunningham wrote: > Hi. > > On Tuesday 24 July 2007 01:23:15 Alan Stern wrote: > > On Mon, 23 Jul 2007, Nigel Cunningham wrote: > > > > > Take a step back for a second. > > > > > > The problem we're facing now is that we're getting some userspace threads, > > > used in processing I/O, that are functioning as exceptions to the "freeze > > > userspace, then freezeable kernel threads" rule. They are only exceptions > > > because of that role in processing I/O - because they're de facto kernel > > > threads. So, if we orient our thinking more in terms of I/O processing and > > > less in terms of the userspace/kernelspace distinction, we'll have a > > > solution: > > > > > > 1) Freeze processes that aren't fs related (ie stop them generating I/O). > > > > The problem here is that with things like FUSE, _every_ process is > > potentially fs related. Nothing prevents a FUSE thread from doing IPC > > with any other thread. > > Yes, but the fuse thread is going to know what other thread it's doing IPC > with, so it can get that thread flagged too. Yes, but that thread may do IPC with yet another one and so on. > > > 2) Flush pending I/O. > > > 3) Freeze filesystems in reverse order of dependency, the primary purpose > > > being to stop them generating further I/O on their metadata. > > > > > > Locks that are being held are only being held because work is being done. > If > > > we progressively focus on threads in terms of their create/process work > > > dependencies, we'll see that the problem isn't at all intractable. > > > > As has been mentioned before, keeping track of all that dependency > > information would be very fragile and time-consuming. > > I disagree. It's at least going to be less fragile and time-consuming then > maintaining new/extra code for kexec. Well, I think the issue is real, so we need to find a solution (the simpler, the better) and that need not be related to kexec. ;-) Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
