Alan Cox 6039d0b777 Merge portions of r208645 and supporting code from the i386 pmap: ... When I pushed down the page queues lock into pmap_is_modified(), I created an ordering dependence: A pmap operation that clears PG_WRITEABLE and calls vm_page_dirty() must perform the call first. Otherwise, pmap_is_modified() could return FALSE without acquiring the page queues lock because the page is not (currently) writeable, and the caller to pmap_is_modified() might believe that the page's dirty field is clear because it has not seen the effect of the vm_page_dirty() call. When I pushed down the page queues lock into pmap_is_modified(), I overlooked one place where this ordering dependence is violated: pmap_enter(). In a rare situation pmap_enter() can be called to replace a dirty mapping to one page with a mapping to another page. (I say rare because replacements generally occur as a result of a copy-on-write fault, and so the old page is not dirty.) This change delays clearing PG_WRITEABLE until after vm_page_dirty() has been called. Fixing the ordering dependency also makes it easy to introduce a small optimization: When pmap_enter() used to replace a mapping to one page with a mapping to another page, it freed the pv entry for the first mapping and later called the pv entry allocator for the new mapping. Now, pmap_enter() attempts to recycle the old pv entry, saving two calls to the pv entry allocator. There is no point in setting PG_WRITEABLE on unmanaged pages, so don't.		2010-06-01 05:18:48 +00:00
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cddl
compile
conf	Change USB_DEBUG to #ifdef and allow it to be turned off. Previously this had	2010-04-22 21:31:34 +00:00
include	Reorganize syscall entry and leave handling.	2010-05-23 18:32:02 +00:00
mdesc
sun4v	Merge portions of r208645 and supporting code from the i386 pmap:	2010-06-01 05:18:48 +00:00