Date: Thu, 9 Jan 2020 08:12:23 -0300 From: Leandro Lupori <leandro.lupori@gmail.com> To: Mark Millard <marklmi@yahoo.com> Cc: Justin Hibbits <chmeeedalf@gmail.com>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, "bdragon@freebsd.org" <bdragon@freebsd.org> Subject: Re: A possible unbounded loop in moea_sync_icache: why sys/vm/mlock_test:mlock__copy_on_write_vnode fails? Message-ID: <CAC7XEcJgXZMBb1q8TrqERWwWHLq9g=NNC0hiG7ZAH7kvASYK1g@mail.gmail.com> In-Reply-To: <022334D3-B60E-440F-A514-8D8002B65CB4@yahoo.com> References: <022334D3-B60E-440F-A514-8D8002B65CB4.ref@yahoo.com> <022334D3-B60E-440F-A514-8D8002B65CB4@yahoo.com>
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Interesting, this looks like the same issue that was fixed on 64-bit some time ago: https://reviews.freebsd.org/D19149. On Thu, Jan 9, 2020 at 3:03 AM Mark Millard via freebsd-ppc < freebsd-ppc@freebsd.org> wrote: > In the statement: > > lim = round_page(va); > > later below in moea_sync_icache, it uses: > > #define round_page(x) (((x) + PAGE_MASK) & ~PAGE_MASK) > > So, for PAGE_MASK==(4096u-1u) the statement translates > to, in essence (the u's are conceptual here): > > lim = ((va)+4095u) & ~4095u; > > That means that if va%4096u==0 then teh result > is lim==va . > > In turn, that means that: > > len = MIN(lim - va, sz); > > results in len==0. > > That in turn means that: > > sz -= len; > > does not change sz. > > Overall result: the loop tesing sz>0 does not > terminate. > > I expect that is why the kyua test: > > sys/vm/mlock_test:mlock__copy_on_write_vnode : > > is failing. > > > The code in question: > > static void > moea_sync_icache(mmu_t mmu, pmap_t pm, vm_offset_t va, vm_size_t sz) > { > struct pvo_entry *pvo; > vm_offset_t lim; > vm_paddr_t pa; > vm_size_t len; > > PMAP_LOCK(pm); > while (sz > 0) { > lim = round_page(va); > len = MIN(lim - va, sz); > pvo = moea_pvo_find_va(pm, va & ~ADDR_POFF, NULL); > if (pvo != NULL) { > pa = (pvo->pvo_pte.pte.pte_lo & PTE_RPGN) | > (va & ADDR_POFF); > moea_syncicache(pa, len); > } > va += len; > sz -= len; > } > PMAP_UNLOCK(pm); > } > > > === > Mark Millard > marklmi at yahoo.com > ( dsl-only.net went > away in early 2018-Mar) > > _______________________________________________ > freebsd-ppc@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-ppc > To unsubscribe, send any mail to "freebsd-ppc-unsubscribe@freebsd.org" >
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