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- Remove Giant from msync(2). Giant is still acquired by the lower layers

Browse source 
if we drop into the pmap or vnode layers.
 - Migrate the handling of zero-length msync(2)s into vm_map_sync() so that
   multithread applications can't change the map between implementing the
   zero-length hack in msync(2) and reacquiring the map lock in
   vm_map_sync().

Reviewed by:	tegge
This commit is contained in:
Alan Cox 2003-11-09 22:09:04 +00:00
parent 65b5d09597
commit 637315ed9c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=122367
2 changed files with 10 additions and 27 deletions
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10
sys/vm/vm_map.c
View file

@ -1952,6 +1952,13 @@ vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
* If syncio is TRUE, dirty pages are written synchronously.
* If invalidate is TRUE, any cached pages are freed as well.
*
* If the size of the region from start to end is zero, we are
* supposed to flush all modified pages within the region containing
* start. Unfortunately, a region can be split or coalesced with
* neighboring regions, making it difficult to determine what the
* original region was. Therefore, we approximate this requirement by
* flushing the current region containing start.
*
* Returns an error if any part of the specified range is not mapped.
*/
int
@ -1973,6 +1980,9 @@ vm_map_sync(
if (!vm_map_lookup_entry(map, start, &entry)) {
vm_map_unlock_read(map);
return (KERN_INVALID_ADDRESS);
} else if (start == end) {
start = entry->start;
end = entry->end;
}
/*
* Make a first pass to check for holes.

27
sys/vm/vm_mmap.c
View file

@ -546,40 +546,13 @@ msync(td, uap)
if ((flags & (MS_ASYNC|MS_INVALIDATE)) == (MS_ASYNC|MS_INVALIDATE))
return (EINVAL);
mtx_lock(&Giant);
map = &td->td_proc->p_vmspace->vm_map;
/*
* XXX Gak! If size is zero we are supposed to sync "all modified
* pages with the region containing addr". Unfortunately, we don't
* really keep track of individual mmaps so we approximate by flushing
* the range of the map entry containing addr. This can be incorrect
* if the region splits or is coalesced with a neighbor.
*/
if (size == 0) {
vm_map_entry_t entry;
vm_map_lock_read(map);
rv = vm_map_lookup_entry(map, addr, &entry);
vm_map_unlock_read(map);
if (rv == FALSE) {
rv = -1;
goto done2;
}
addr = entry->start;
size = entry->end - entry->start;
}
/*
* Clean the pages and interpret the return value.
*/
rv = vm_map_sync(map, addr, addr + size, (flags & MS_ASYNC) == 0,
(flags & MS_INVALIDATE) != 0);
done2:
mtx_unlock(&Giant);
switch (rv) {
case KERN_SUCCESS:
return (0);