svn commit: r350002 - head/sys/riscv/riscv
Mark Johnston
markj at FreeBSD.org
Mon Jul 15 15:43:16 UTC 2019
Author: markj
Date: Mon Jul 15 15:43:15 2019
New Revision: 350002
URL: https://svnweb.freebsd.org/changeset/base/350002
Log:
Fix reference counting in pmap_ts_referenced() on RISC-V.
pmap_ts_referenced() does not necessarily clear the access bit from
all accessed mappings of a given page. Thus, if a scan of the mappings
needs to be restarted, we should be careful to avoid double-counting
accessed mappings whose access bits were not cleared in a previous
attempt.
Reported by: alc
Reviewed by: alc
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D20926
Modified:
head/sys/riscv/riscv/pmap.c
Modified: head/sys/riscv/riscv/pmap.c
==============================================================================
--- head/sys/riscv/riscv/pmap.c Mon Jul 15 15:07:55 2019 (r350001)
+++ head/sys/riscv/riscv/pmap.c Mon Jul 15 15:43:15 2019 (r350002)
@@ -3950,12 +3950,12 @@ pmap_ts_referenced(vm_page_t m)
pt_entry_t *l3, l3e;
vm_paddr_t pa;
vm_offset_t va;
- int md_gen, pvh_gen, ret;
+ int cleared, md_gen, not_cleared, pvh_gen;
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("pmap_ts_referenced: page %p is not managed", m));
SLIST_INIT(&free);
- ret = 0;
+ cleared = 0;
pa = VM_PAGE_TO_PHYS(m);
pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy : pa_to_pvh(pa);
@@ -3963,6 +3963,7 @@ pmap_ts_referenced(vm_page_t m)
rw_rlock(&pvh_global_lock);
rw_wlock(lock);
retry:
+ not_cleared = 0;
if ((pvf = TAILQ_FIRST(&pvh->pv_list)) == NULL)
goto small_mappings;
pv = pvf;
@@ -4013,8 +4014,9 @@ retry:
(l2e & PTE_SW_WIRED) == 0) {
pmap_clear_bits(l2, PTE_A);
pmap_invalidate_page(pmap, va);
- }
- ret++;
+ cleared++;
+ } else
+ not_cleared++;
}
PMAP_UNLOCK(pmap);
/* Rotate the PV list if it has more than one entry. */
@@ -4023,7 +4025,7 @@ retry:
TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
pvh->pv_gen++;
}
- if (ret >= PMAP_TS_REFERENCED_MAX)
+ if (cleared + not_cleared >= PMAP_TS_REFERENCED_MAX)
goto out;
} while ((pv = TAILQ_FIRST(&pvh->pv_list)) != pvf);
small_mappings:
@@ -4062,8 +4064,9 @@ small_mappings:
*/
pmap_clear_bits(l3, PTE_A);
pmap_invalidate_page(pmap, pv->pv_va);
- }
- ret++;
+ cleared++;
+ } else
+ not_cleared++;
}
PMAP_UNLOCK(pmap);
/* Rotate the PV list if it has more than one entry. */
@@ -4072,13 +4075,13 @@ small_mappings:
TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
m->md.pv_gen++;
}
- } while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && ret <
- PMAP_TS_REFERENCED_MAX);
+ } while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && cleared +
+ not_cleared < PMAP_TS_REFERENCED_MAX);
out:
rw_wunlock(lock);
rw_runlock(&pvh_global_lock);
vm_page_free_pages_toq(&free, false);
- return (ret);
+ return (cleared + not_cleared);
}
/*
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