14b5a3c7d5
This KASSERT is overzealous because of the following race condition:
1) A managed page which is currently in PQ_LAUNDRY is freed.
vm_page_free_prep calls vm_page_dequeue_deferred()
The page state is:
PQ_LAUNDRY, PGA_DEQUEUE|PGA_ENQUEUED
2) The laundry worker comes around and pick up the page and calls
vm_pageout_defer(m, PQ_LAUNDRY, true) to check if page is still in the
queue. We do a vm_page_astate_load and get
PQ_LAUNDRY, PGA_DEQUEUE|PGA_ENQUEUED
as per above.
3) The laundry worker is pre-empted and another thread allocates our page
from the free pool. For example vm_page_alloc_domain_after calls
vm_page_dequeue() and sets VPO_UNMANAGED because we are allocating for
an OBJT_UNMANAGED object.
The page state is:
PQ_NONE, 0 - VPO_UNMANAGED
4) The laundry worker resumes, and processes vm_pageout_defer based on the
stale astate which leads to a call to vm_page_pqbatch_submit, which will
trip on the KASSERT.
Submitted by: mlaier
Reviewed by: markj, rlibby
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D28563
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| .. | ||
| _vm_phys.h | ||
| _vm_radix.h | ||
| default_pager.c | ||
| device_pager.c | ||
| memguard.c | ||
| memguard.h | ||
| phys_pager.c | ||
| pmap.h | ||
| redzone.c | ||
| redzone.h | ||
| sg_pager.c | ||
| swap_pager.c | ||
| swap_pager.h | ||
| uma_core.c | ||
| uma_dbg.c | ||
| uma_dbg.h | ||
| uma_int.h | ||
| uma.h | ||
| vm_domainset.c | ||
| vm_domainset.h | ||
| vm_dumpset.h | ||
| vm_extern.h | ||
| vm_fault.c | ||
| vm_glue.c | ||
| vm_init.c | ||
| vm_kern.c | ||
| vm_kern.h | ||
| vm_map.c | ||
| vm_map.h | ||
| vm_meter.c | ||
| vm_mmap.c | ||
| vm_object.c | ||
| vm_object.h | ||
| vm_page.c | ||
| vm_page.h | ||
| vm_pageout.c | ||
| vm_pageout.h | ||
| vm_pagequeue.h | ||
| vm_pager.c | ||
| vm_pager.h | ||
| vm_param.h | ||
| vm_phys.c | ||
| vm_phys.h | ||
| vm_radix.c | ||
| vm_radix.h | ||
| vm_reserv.c | ||
| vm_reserv.h | ||
| vm_swapout_dummy.c | ||
| vm_swapout.c | ||
| vm_unix.c | ||
| vm.h | ||
| vnode_pager.c | ||
| vnode_pager.h | ||