Messages in this thread | | | Subject | Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() | From | Peter Zijlstra <> | Date | Thu, 07 Jan 2010 22:44:43 +0100 |
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On Thu, 2010-01-07 at 10:44 -0800, Linus Torvalds wrote: > > On Thu, 7 Jan 2010, Linus Torvalds wrote: > > > > For example: there's no real reason why we take mmap_sem for writing when > > extending an existing vma. And while 'brk()' is a very oldfashioned way of > > doing memory management, it's still quite common. So rather than looking > > at subtle lockless algorithms, why not look at doing the common cases of > > an extending brk? Make that one take the mmap_sem for _reading_, and then > > do the extending of the brk area with a simple cmpxchg or something? > > I didn't use cmpxchg, because we actually want to update both > 'current->brk' _and_ the vma->vm_end atomically, so here's a totally > untested patch that uses the page_table_lock spinlock for it instead (it > could be a new spinlock, not worth it). > > It's also totally untested and might be horribly broken. But you get the > idea. > > We could probably do things like this in regular mmap() too for the > "extend a mmap" case. brk() is just especially simple.
I haven't yet looked at the patch, but isn't expand_stack() kinda like what you want? That serializes using anon_vma_lock().
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