uvm_mapanon() is called in two occasions: mmap(2) and sigaltstack(2).
Both code paths are obviously in process context an can sleep. That
explains why none of them set the UVM_FLAG_TRYLOCK when calling such
function.
The diff below removes support for this flag. This introduces a
difference with uvm_map(9) but simplifies the overall code. Removing
support for an unneeded "try" variant also means the lock can be grabbed
earlier. This is a requirement to not lose atomicity between
uvm_mapanon() and uvm_map_pageable() in mmap(2).
ok?
Index: uvm/uvm_map.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_map.c,v
retrieving revision 1.250
diff -u -p -r1.250 uvm_map.c
--- uvm/uvm_map.c 2 Nov 2019 16:41:57 -0000 1.250
+++ uvm/uvm_map.c 8 Nov 2019 16:43:30 -0000
@@ -951,9 +951,9 @@ uvm_mapanon(struct vm_map *map, vaddr_t
KASSERT((map->flags & VM_MAP_ISVMSPACE) == VM_MAP_ISVMSPACE);
KASSERT(map != kernel_map);
KASSERT((map->flags & UVM_FLAG_HOLE) == 0);
-
KASSERT((map->flags & VM_MAP_INTRSAFE) == 0);
splassert(IPL_NONE);
+ KASSERT((flags & UVM_FLAG_TRYLOCK) == 0);
/*
* We use pmap_align and pmap_offset as alignment and offset variables.
@@ -989,14 +989,7 @@ uvm_mapanon(struct vm_map *map, vaddr_t
if (new == NULL)
return(ENOMEM);
- if (flags & UVM_FLAG_TRYLOCK) {
- if (vm_map_lock_try(map) == FALSE) {
- error = EFAULT;
- goto out;
- }
- } else
- vm_map_lock(map);
-
+ vm_map_lock(map);
first = last = NULL;
if (flags & UVM_FLAG_FIXED) {
/*
@@ -1114,7 +1107,7 @@ unlock:
* destroy free-space entries.
*/
uvm_unmap_detach(&dead, 0);
-out:
+
if (new)
uvm_mapent_free(new);
return error;
