Messages in this thread | | | Date | Fri, 1 Nov 2013 11:55:03 -0700 | Subject | Re: [PATCH 0/4] per anon_vma lock and turn anon_vma rwsem lock to rwlock_t | From | Linus Torvalds <> |
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On Fri, Nov 1, 2013 at 11:47 AM, Michel Lespinasse <walken@google.com> wrote: > > Should copy Andrea on this. I talked with him during KS, and there are > no current in-tree users who are doing such sleeping; however there > are prospective users for networking (RDMA) or GPU stuff who want to > use this to let hardware directly copy data into user mappings.
Tough.
I spoke up the first time this came up and I'll say the same thing again: we're not screwing over the VM subsystem because some crazy user might want to do crazy and stupid things that nobody sane cares about.
The whole "somebody might want to .." argument is just irrelevant. Some people want to sleep in interrupt handlers too, or while holding random spinlocks. Too bad. They don't get to, because doing that results in problems for the rest of the system.
Our job in the kernel is to do the best job technically that we can. And sometimes that very much involves saying "No, you can't do that".
We have limitations in the kernel. The stack is of limited size. You can't allocate arbitrarily sized memory. You must follow some very strict rules.
If people can't handle that, then they can go cry to mommy, and go back to writing user mode code. In the kernel, you have to live with certain constraints that makes the kernel better.
Linus
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