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- Make the acquisition of Giant in vm_fault_unwire() conditional on the

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pmap.  For the kernel pmap, Giant is not required.  In general, for
   other pmaps, Giant is required by i386's pmap_pte() implementation.
   Specifically, the use of PMAP2/PADDR2 is synchronized by Giant.
   Note: In principle, updates to the kernel pmap's wired count could be
   lost without Giant.  However, in practice, we never use the kernel
   pmap's wired count.  This will be resolved when pmap locking appears.
 - With the above change, cpu_thread_clean() and uma_large_free() need
   not acquire Giant.  (The first case is simply the revival of
   i386/i386/vm_machdep.c's revision 1.226 by peter.)
This commit is contained in:
Alan Cox 2004-03-10 04:44:43 +00:00
parent fe5a02c927
commit 5d328ed44b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=126793
3 changed files with 5 additions and 15 deletions
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2
sys/i386/i386/vm_machdep.c
View file

@ -320,10 +320,8 @@ cpu_thread_clean(struct thread *td)
* XXX do we need to move the TSS off the allocated pages
* before freeing them? (not done here)
*/
mtx_lock(&Giant);
kmem_free(kernel_map, (vm_offset_t)pcb->pcb_ext,
ctob(IOPAGES + 1));
mtx_unlock(&Giant);
pcb->pcb_ext = 0;
}
}

12
sys/vm/uma_core.c
View file

@ -2052,17 +2052,7 @@ void
uma_large_free(uma_slab_t slab)
{
vsetobj((vm_offset_t)slab->us_data, kmem_object);
/*
* XXX: We get a lock order reversal if we don't have Giant:
* vm_map_remove (locks system map) -> vm_map_delete ->
* vm_map_entry_unwire -> vm_fault_unwire -> mtx_lock(&Giant)
*/
if (!mtx_owned(&Giant)) {
mtx_lock(&Giant);
page_free(slab->us_data, slab->us_size, slab->us_flags);
mtx_unlock(&Giant);
} else
page_free(slab->us_data, slab->us_size, slab->us_flags);
page_free(slab->us_data, slab->us_size, slab->us_flags);
uma_zfree_internal(slabzone, slab, NULL, 0);
}

6
sys/vm/vm_fault.c
View file

@ -1081,7 +1081,8 @@ vm_fault_unwire(map, start, end)
pmap = vm_map_pmap(map);
mtx_lock(&Giant);
if (pmap != kernel_pmap)
mtx_lock(&Giant);
/*
* Since the pages are wired down, we must be able to get their
* mappings from the physical map system.
@ -1095,7 +1096,8 @@ vm_fault_unwire(map, start, end)
vm_page_unlock_queues();
}
}
mtx_unlock(&Giant);
if (pmap != kernel_pmap)
mtx_unlock(&Giant);
}
/*