From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id 9FAE96B0028 for ; Thu, 22 Mar 2018 20:55:51 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id d7so6813949qtm.6 for ; Thu, 22 Mar 2018 17:55:51 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id k5si7505157qkk.321.2018.03.22.17.55.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 22 Mar 2018 17:55:50 -0700 (PDT) From: jglisse@redhat.com Subject: [PATCH 03/15] mm/hmm: HMM should have a callback before MM is destroyed v3 Date: Thu, 22 Mar 2018 20:55:15 -0400 Message-Id: <20180323005527.758-4-jglisse@redhat.com> In-Reply-To: <20180323005527.758-1-jglisse@redhat.com> References: <20180323005527.758-1-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Andrew Morton , linux-kernel@vger.kernel.org, Ralph Campbell , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Evgeny Baskakov , Mark Hairgrove From: Ralph Campbell The hmm_mirror_register() function registers a callback for when the CPU pagetable is modified. Normally, the device driver will call hmm_mirror_unregister() when the process using the device is finished. However, if the process exits uncleanly, the struct_mm can be destroyed with no warning to the device driver. Changed since v1: - dropped VM_BUG_ON() - cc stable Changed since v2: - drop stable - Split list removale and call to driver release callback. This allow the release callback to wait on any pending fault handler without deadlock. Signed-off-by: Ralph Campbell Signed-off-by: JA(C)rA'me Glisse Reviewed-by: John Hubbard Cc: Evgeny Baskakov Cc: Mark Hairgrove --- include/linux/hmm.h | 10 ++++++++++ mm/hmm.c | 29 ++++++++++++++++++++++++++++- 2 files changed, 38 insertions(+), 1 deletion(-) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 36dd21fe5caf..fa7b51f65905 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -218,6 +218,16 @@ enum hmm_update_type { * @update: callback to update range on a device */ struct hmm_mirror_ops { + /* release() - release hmm_mirror + * + * @mirror: pointer to struct hmm_mirror + * + * This is called when the mm_struct is being released. + * The callback should make sure no references to the mirror occur + * after the callback returns. + */ + void (*release)(struct hmm_mirror *mirror); + /* sync_cpu_device_pagetables() - synchronize page tables * * @mirror: pointer to struct hmm_mirror diff --git a/mm/hmm.c b/mm/hmm.c index 320545b98ff5..8116727766f7 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -160,6 +160,32 @@ static void hmm_invalidate_range(struct hmm *hmm, up_read(&hmm->mirrors_sem); } +static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm) +{ + struct hmm_mirror *mirror; + struct hmm *hmm = mm->hmm; + + down_write(&hmm->mirrors_sem); + mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror, + list); + while (mirror) { + list_del_init(&mirror->list); + if (mirror->ops->release) { + /* + * Drop mirrors_sem so callback can wait on any pending + * work that might itself trigger mmu_notifier callback + * and thus would deadlock with us. + */ + up_write(&hmm->mirrors_sem); + mirror->ops->release(mirror); + down_write(&hmm->mirrors_sem); + } + mirror = list_first_entry_or_null(&hmm->mirrors, + struct hmm_mirror, list); + } + up_write(&hmm->mirrors_sem); +} + static void hmm_invalidate_range_start(struct mmu_notifier *mn, struct mm_struct *mm, unsigned long start, @@ -185,6 +211,7 @@ static void hmm_invalidate_range_end(struct mmu_notifier *mn, } static const struct mmu_notifier_ops hmm_mmu_notifier_ops = { + .release = hmm_release, .invalidate_range_start = hmm_invalidate_range_start, .invalidate_range_end = hmm_invalidate_range_end, }; @@ -230,7 +257,7 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror) struct hmm *hmm = mirror->hmm; down_write(&hmm->mirrors_sem); - list_del(&mirror->list); + list_del_init(&mirror->list); up_write(&hmm->mirrors_sem); } EXPORT_SYMBOL(hmm_mirror_unregister); -- 2.14.3