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Recursion on the free page queue mutex occurred when UMA needed to allocate

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a new page of radix trie nodes to complete a vm_radix_insert() operation
that was requested by vm_page_cache().  Specifically, vm_page_cache()
already held the free page queue lock when UMA tried to acquire it through
a call to vm_page_alloc().  This code path no longer exists, so there is no
longer any reason to allow recursion on the free page queue mutex.

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Reviewed by:	kib, markj
Tested by:	pho
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D8628
This commit is contained in:
Alan Cox 2016-11-27 01:42:53 +00:00
parent 77cb4d3e50
commit ba67369628
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=309203
1 changed files with 8 additions and 7 deletions
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15
sys/vm/vm_page.c
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@ -1512,19 +1512,17 @@ vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
}
/*
* The page allocation request can came from consumers which already
* hold the free page queue mutex, like vm_page_insert() in
* vm_page_cache().
* Allocate a page if the number of free pages exceeds the minimum
* for the request class.
*/
mtx_lock_flags(&vm_page_queue_free_mtx, MTX_RECURSE);
mtx_lock(&vm_page_queue_free_mtx);
if (vm_cnt.v_free_count > vm_cnt.v_free_reserved ||
(req_class == VM_ALLOC_SYSTEM &&
vm_cnt.v_free_count > vm_cnt.v_interrupt_free_min) ||
(req_class == VM_ALLOC_INTERRUPT &&
vm_cnt.v_free_count > 0)) {
/*
* Allocate from the free queue if the number of free pages
* exceeds the minimum for the request class.
* Can we allocate the page from a reservation?
*/
#if VM_NRESERVLEVEL > 0
if (object == NULL || (object->flags & (OBJ_COLORED |
@ -1532,6 +1530,9 @@ vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
vm_reserv_alloc_page(object, pindex, mpred)) == NULL)
#endif
{
/*
* If not, allocate it from the free page queues.
*/
m = vm_phys_alloc_pages(object != NULL ?
VM_FREEPOOL_DEFAULT : VM_FREEPOOL_DIRECT, 0);
#if VM_NRESERVLEVEL > 0
@ -1841,7 +1842,7 @@ vm_page_alloc_freelist(int flind, int req)
/*
* Do not allocate reserved pages unless the req has asked for it.
*/
mtx_lock_flags(&vm_page_queue_free_mtx, MTX_RECURSE);
mtx_lock(&vm_page_queue_free_mtx);
if (vm_cnt.v_free_count > vm_cnt.v_free_reserved ||
(req_class == VM_ALLOC_SYSTEM &&
vm_cnt.v_free_count > vm_cnt.v_interrupt_free_min) ||