Messages in this thread | | | Subject | Re: process 'stuck' at exit. | From | Darren Hart <> | Date | Tue, 10 Dec 2013 14:58:19 -0800 |
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On Tue, 2013-12-10 at 14:48 -0800, Linus Torvalds wrote: > On Tue, Dec 10, 2013 at 2:42 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > > > > And yes, I remember that we do not do an extra check for the fshared > > case, because get_user_pages_fast() should do it for us already. If > > not we are fubared not only in the futex code. > > Yeah. It turns out we do do the access check indirectly - by looking > at the PAGE_USER bit, even if we don't necessarily check the actual > limits. So get_user_pages_fast() is fine. > > > But there is a subtle detail: > > Yup, see my email from ten minutes ago, we found the same thing. And > that would seem to explain the endless loop, and also the timing > (since Dave mentions he started doing large-pages lately). > > So I think the "__get_user_pages_fast(address, 1, !ro, &page)" thing > should work. > > Dave, can you re-create that trinity run and test that patch? I think > we've got this, but it might be nice to leave the hung machine up and > running until it's verified.. Although I don't really see what else we > could need or get out of it, so..
Would it be possible to limit the options to only pass FUTEX_CMP_REQUEUE and a read-only uaddr? That should improve confidence when it doesn't fail :-)
-- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel
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