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); } /* _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
