On Thu, 2008-05-08 at 09:11 -0700, Linus Torvalds wrote: > > On Thu, 8 May 2008, Linus Torvalds wrote: > > > > Also, we'd need to make it > > > > unsigned short flag:1; > > > > _and_ change spinlock_types.h to make the spinlock size actually match the > > required size (right now we make it an "unsigned int slock" even when we > > actually only use 16 bits). > > Btw, this is an issue only on 32-bit x86, because on 64-bit one we already > have the padding due to the alignment of the 64-bit pointers in the > list_head (so there's already empty space there). > > On 32-bit, the alignment of list-head is obviously just 32 bits, so right > now the structure is "perfectly packed" and doesn't have any empty space. > But that's just because the spinlock is unnecessarily big. > > (Of course, if anybody really uses NR_CPUS >= 256 on 32-bit x86, then the > structure really will grow. That's a very odd configuration, though, and > not one I feel we really need to care about).
Another possibility, would something like this work? /* * null out the begin function, no new begin calls can be made */ rcu_assing_pointer(my_notifier.invalidate_start_begin, NULL); /* * lock/unlock all rmap locks in any order - this ensures that any * pending start() will have its end() function called. */ mm_barrier(mm); /* * now that no new start() call can be made and all start()/end() pairs * are complete we can remove the notifier. */ mmu_notifier_remove(mm, my_notifier); This requires a mmu_notifier instance per attached mm and that __mmu_notifier_invalidate_range_start() uses rcu_dereference() to obtain the function. But I think its enough to ensure that: for each start an end will be called It can however happen that end is called without start - but we could handle that I think. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
