Hi,
Having spent quite some hours figuring out why the kernel panics when I free
memory allocated through uvm_km_kmemalloc() with uvm_km_free()
("pmap_remove_pte: managed page without PG_PVLIST for <address>" on amd64),
I added the following clarification to uvm(9):
Index: uvm.9
===================================================================
RCS file: /cvs/openbsd/src/share/man/man9/uvm.9,v
retrieving revision 1.42
diff -u -a -r1.42 uvm.9
--- uvm.9 9 Nov 2010 16:03:38 -0000 1.42
+++ uvm.9 8 Dec 2010 15:41:28 -0000
@@ -518,7 +518,7 @@
.Fn uvm_km_zalloc
functions allocate
.Fa size
-bytes of wired kernel memory in map
+bytes of page-aligned wired kernel memory in map
.Fa map .
In addition to allocation,
.Fn uvm_km_zalloc
@@ -532,9 +532,15 @@
.Fn uvm_km_alloc1
function allocates and returns
.Fa size
-bytes of wired memory in the kernel map, zeroing the memory if the
+bytes of page-aligned wired memory in the kernel map, zeroing the memory if
+the
.Fa zeroit
-argument is non-zero.
+argument is non-zero. Unless called on an interrupt-safe map, if memory is
+currently unavailable,
+.Fn uvm_km_alloc1
+may sleep to wait for resources to be released by other processes. If not
+enough memory is available, this function returns
+.Dv NULL .
.Pp
The
.Fn uvm_km_kmemalloc
@@ -607,10 +613,15 @@
.Fa size
bytes of memory in the kernel map, starting at address
.Fa addr .
+The memory must have been allocated with
+.Fn uvm_km_alloc ,
+.Fn uvm_km_zalloc
+or
+.Fn uvm_km_alloc1 .
.Fn uvm_km_free_wakeup
-calls
-.Fn thread_wakeup
-on the map before unlocking the map.
+wakes up any processes waiting for memory on the map (via
+.Fn thread_wakeup )
+before unlocking the map.
.Sh ALLOCATION OF PHYSICAL MEMORY
.nr nS 1
.Ft struct vm_page *
Is this correct? And if so, any chance this could go in?
Regards,
Wouter Coene
