> Date: Fri, 1 Oct 2021 20:07:20 +0200
> From: Martin Pieuchot <m...@openbsd.org>
>
> amaps operation are already serialized by their own lock so it is
> possible to free them w/o holding the KERNEL_LOCK(). This has been
> tested by many as part of the UVM unlocking diff.
>
> ok?
ok kettenis@
but please wait with putting in further diffs until Theo has started
building snaps
> Index: uvm/uvm_map.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_map.c,v
> retrieving revision 1.277
> diff -u -p -r1.277 uvm_map.c
> --- uvm/uvm_map.c 17 Jun 2021 16:10:39 -0000 1.277
> +++ uvm/uvm_map.c 1 Oct 2021 17:02:29 -0000
> @@ -1570,9 +1570,15 @@ uvm_unmap_detach(struct uvm_map_deadq *d
> int waitok = flags & UVM_PLA_WAITOK;
>
> TAILQ_FOREACH_SAFE(entry, deadq, dfree.deadq, tmp) {
> + /* Drop reference to amap, if we've got one. */
> + if (entry->aref.ar_amap)
> + amap_unref(entry->aref.ar_amap,
> + entry->aref.ar_pageoff,
> + atop(entry->end - entry->start),
> + flags & AMAP_REFALL);
> +
> /* Skip entries for which we have to grab the kernel lock. */
> - if (entry->aref.ar_amap || UVM_ET_ISSUBMAP(entry) ||
> - UVM_ET_ISOBJ(entry))
> + if (UVM_ET_ISSUBMAP(entry) || UVM_ET_ISOBJ(entry))
> continue;
>
> TAILQ_REMOVE(deadq, entry, dfree.deadq);
> @@ -1586,13 +1592,6 @@ uvm_unmap_detach(struct uvm_map_deadq *d
> while ((entry = TAILQ_FIRST(deadq)) != NULL) {
> if (waitok)
> uvm_pause();
> - /* Drop reference to amap, if we've got one. */
> - if (entry->aref.ar_amap)
> - amap_unref(entry->aref.ar_amap,
> - entry->aref.ar_pageoff,
> - atop(entry->end - entry->start),
> - flags & AMAP_REFALL);
> -
> /* Drop reference to our backing object, if we've got one. */
> if (UVM_ET_ISSUBMAP(entry)) {
> /* ... unlikely to happen, but play it safe */
>
>
