Messages in this thread | | | Date | Mon, 22 Jul 2013 17:42:49 -0700 | Subject | Re: 3.11-rc regression bisected: s2disk does not work (was Re: [PATCH v3 13/16] futex: use freezable blocking call) | From | Colin Cross <> |
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On Mon, Jul 22, 2013 at 5:32 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Mon, Jul 22, 2013 at 4:55 PM, Colin Cross <ccross@android.com> wrote: >> >> I think the right solution is to add a flag to the freezing task that >> marks it unfreezable. I think PF_NOFREEZE would work, although it is >> normally used on kernel threads, can you see if the attached patch >> helps? > > Hmm. That does seem to be the right thing to do, but I wonder about > the *other* callers of freeze_processes() IOW, kexec and friends. > > So maybe we should do this in {freeze|thaw}_processes() itself, and > just make the rule be that the caller of freeze_processes() itself is > obviously not frozen, and has to be the same one that then thaws > things? > > Colin? Rafael? Comments? > > Linus
I was worried about clearing the flag in thaw_processes(). If a kernel thread with PF_NOFREEZE set ever called thaw_processes(), which autosleep might do, it would clear the flag. Or if a different thread called freeze_processes() and thaw_processes(). All the other callers besides the SNAPSHOT_FREEZE ioctl stay in the kernel between freeze_processes() and thaw_processes(), which makes the fanout of places that could call try_to_freeze() much more controllable.
Using a new flag that operates like PF_NOFREEZE but doesn't conflict with it, or a nofreeze_depth counter, would also work.
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