On Mon, Feb 09, 2004 at 10:27:18PM -0800, Matt Thomas wrote:
>At 06:03 PM 2/9/2004, YAMAMOTO Takashi wrote:
>>hi,
>>
>> > Module Name:  src
>> > Committed By: matt
>> > Date:         Tue Feb 10 01:30:49 UTC 2004
>> >
>> > Modified Files:
>> >       src/sys/uvm: uvm.h uvm_km.c uvm_map.c uvm_map.h uvm_map_i.h
>> >
>> > Log Message:
>> > Back out the changes in
>> > http://mail-index.netbsd.org/source-changes/2004/01/29/0027.html
>> > since they don't really fix the problem.
>>
>>what do you think a "real" fix is?
>>are you going to fix all callers of uvm_unmap to be safe to sleep?
>>
>>(i'm not objecting to the backout)
>
>I don't know quite yet.  Passing in UVM_FLAG_NOMERGE on the map will
>will guarantee that uvm_unmap will not block since the uvm_map_entry
>will never be split.  But it doesn't seem to be a good solution.

how can asserting UVM_FLAG_NOMERGE prevent splitting unless the
allocation is less than three pages in size?  can't i simply make a
three page allocation with UVM_FLAG_NOMERGE set and then unmap the
middle page?

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