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struct vm_map:

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The lock structure cannot be the first element of the vm_map
	because this can result in livelock between two or more system
	processes trying to kmem_alloc_wait.
This commit is contained in:
alc 1999-08-23 18:08:34 +00:00
parent 9d3d71aa49
commit 5589e2e37e
1 changed files with 9 additions and 2 deletions
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11
sys/vm/vm_map.h
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@ -61,7 +61,7 @@
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*
* $Id: vm_map.h,v 1.45 1999/08/16 18:21:09 alc Exp $
* $Id: vm_map.h,v 1.46 1999/08/18 03:56:57 mjacob Exp $
*/
/*
@ -143,10 +143,17 @@ vm_map_entry_set_behavior(struct vm_map_entry *entry, u_char behavior)
* by address. A single hint is provided to start
* searches again from the last successful search,
* insertion, or removal.
*
* Note: the lock structure cannot be the first element of vm_map
* because this can result in a running lockup between two or more
* system processes trying to kmem_alloc_wait() due to kmem_alloc_wait()
* and free tsleep/waking up 'map' and the underlying lockmgr also
* sleeping and waking up on 'map'. The lockup occurs when the map fills
* up. The 'exec' map, for example.
*/
struct vm_map {
struct lock lock; /* Lock for map data */
struct vm_map_entry header; /* List of entries */
struct lock lock; /* Lock for map data */
int nentries; /* Number of entries */
vm_size_t size; /* virtual size */
unsigned char system_map; /* Am I a system map? */