From owner-freebsd-arm@FreeBSD.ORG Wed Jul 8 15:07:32 2009 Return-Path: Delivered-To: freebsd-arm@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 92097106567D; Wed, 8 Jul 2009 15:07:32 +0000 (UTC) (envelope-from tinguely@casselton.net) Received: from casselton.net (casselton.net [63.165.140.2]) by mx1.freebsd.org (Postfix) with ESMTP id 46AAE8FC1A; Wed, 8 Jul 2009 15:07:31 +0000 (UTC) (envelope-from tinguely@casselton.net) Received: from casselton.net (localhost [127.0.0.1]) by casselton.net (8.14.3/8.14.3) with ESMTP id n68F7VFn070525; Wed, 8 Jul 2009 10:07:31 -0500 (CDT) (envelope-from tinguely@casselton.net) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=casselton.net; s=ccnMail; t=1247065651; bh=OYJ2Lcl8qznNEF0P62QsFg/AaEF2g4d54m6T/epMI00=; h=Date:From:Message-Id:To:Subject:Cc:In-Reply-To; b=MLt+DNs5NdBaswfRCrbvuElvvDk0icwM6D/hWBlBjP7LeBC4ZMZmST7Y+rKmF18jB kl0gfdyPAM0XhAXK+TR233sY+WvEdBgUP44Ca/5FIchTKI18wZhAgW4szkkKE+g1iO ofkAm+CNfz/rz7rgizFd5VwJtbGzzJy1VEyaaYIg= Received: (from tinguely@localhost) by casselton.net (8.14.3/8.14.2/Submit) id n68F7Vsu070524; Wed, 8 Jul 2009 10:07:31 -0500 (CDT) (envelope-from tinguely) Date: Wed, 8 Jul 2009 10:07:31 -0500 (CDT) From: Mark Tinguely Message-Id: <200907081507.n68F7Vsu070524@casselton.net> To: mih@semihalf.com, tinguely@casselton.net In-Reply-To: <4A54A6B2.1020400@semihalf.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.3.2 (casselton.net [127.0.0.1]); Wed, 08 Jul 2009 10:07:31 -0500 (CDT) Cc: stas@FreeBSD.org, freebsd-arm@FreeBSD.org Subject: Re: pmap problem in FreeBSD current X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to the StrongARM Processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 08 Jul 2009 15:07:33 -0000 > Hello Mark, > Thank you for looking again on r194459. > > I've tried to compile kernel using your patch with > changes regarding PG_WRITABLE and arm_unmap_nocache(), > but it didn't help. > > My problems are rather related to memory corruption, which > I've observed in uma_core (pointers had bad values and > count of free items in slab had negative value). > > I am still concerned about LOR, which has appeared in > svn commit r194459 (I wrote about it in my first mail). > Could you take a look at this LOR? > > Thanks for your help. > > Best regards, > Michał Hajduk I don't think this is a corruption issue but an allocation of a l2_bucket issue. The kernel map is locked to do the kenter. A new bucket is needed, UMA is called and the new page is kenter into the map. In pmap_enter_pv() before we allocate a pv_entry, we turn off the kmap lock. I am not sure if the kmap lock should be turned off in the pmap_alloc_l2_bucket(), or the caller, but here is a quick manually made kmap lock disable patch: I still think the last "vm_page_flag_clear(pg, PG_WRITEABLE);" needs to be removed from pmap_nuke_pv(). All dangling kenters need to be kremoved ... ------------------------ /* * Returns a pointer to the L2 bucket associated with the specified pmap * and VA. * * If no L2 bucket exists, perform the necessary allocations to put an L2 * bucket/page table in place. * * Note that if a new L2 bucket/page was allocated, the caller *must* * increment the bucket occupancy counter appropriately *before* * releasing the pmap's lock to ensure no other thread or cpu deallocates * the bucket/page in the meantime. */ static struct l2_bucket * pmap_alloc_l2_bucket(pmap_t pm, vm_offset_t va) { struct l2_dtable *l2; struct l2_bucket *l2b; u_short l1idx; + int km = 0; l1idx = L1_IDX(va); PMAP_ASSERT_LOCKED(pm); + if ((pm != pmap_kernel()) && PMAP_OWNED(pmap_kernel()) { + km = 1; + PMAP_UNLOCK(pmap_kernel()); + } mtx_assert(&vm_page_queue_mtx, MA_OWNED); if ((l2 = pm->pm_l2[L2_IDX(l1idx)]) == NULL) { /* * No mapping at this address, as there is * no entry in the L1 table. * Need to allocate a new l2_dtable. */ again_l2table: PMAP_UNLOCK(pm); vm_page_unlock_queues(); if ((l2 = pmap_alloc_l2_dtable()) == NULL) { vm_page_lock_queues(); PMAP_LOCK(pm); + if (km) + PMAP_LOCK(pmap_kernel()); return (NULL); } vm_page_lock_queues(); PMAP_LOCK(pm); if (pm->pm_l2[L2_IDX(l1idx)] != NULL) { PMAP_UNLOCK(pm); vm_page_unlock_queues(); uma_zfree(l2table_zone, l2); vm_page_lock_queues(); PMAP_LOCK(pm); l2 = pm->pm_l2[L2_IDX(l1idx)]; if (l2 == NULL) goto again_l2table; /* * Someone already allocated the l2_dtable while * we were doing the same. */ } else { bzero(l2, sizeof(*l2)); /* * Link it into the parent pmap */ pm->pm_l2[L2_IDX(l1idx)] = l2; } } l2b = &l2->l2_bucket[L2_BUCKET(l1idx)]; /* * Fetch pointer to the L2 page table associated with the address. */ if (l2b->l2b_kva == NULL) { pt_entry_t *ptep; /* * No L2 page table has been allocated. Chances are, this * is because we just allocated the l2_dtable, above. */ again_ptep: PMAP_UNLOCK(pm); vm_page_unlock_queues(); ptep = (void*)uma_zalloc(l2zone, M_NOWAIT|M_USE_RESERVE); vm_page_lock_queues(); PMAP_LOCK(pm); if (l2b->l2b_kva != 0) { /* We lost the race. */ PMAP_UNLOCK(pm); vm_page_unlock_queues(); uma_zfree(l2zone, ptep); vm_page_lock_queues(); PMAP_LOCK(pm); if (l2b->l2b_kva == 0) goto again_ptep; return (l2b); } l2b->l2b_phys = vtophys(ptep); if (ptep == NULL) { /* * Oops, no more L2 page tables available at this * time. We may need to deallocate the l2_dtable * if we allocated a new one above. */ if (l2->l2_occupancy == 0) { pm->pm_l2[L2_IDX(l1idx)] = NULL; pmap_free_l2_dtable(l2); } + if (km) + PMAP_LOCK(pmap_kernel()); return (NULL); } l2->l2_occupancy++; l2b->l2b_kva = ptep; l2b->l2b_l1idx = l1idx; } + if (km) + PMAP_LOCK(pmap_kernel()); return (l2b); }