From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 759CEC77B78 for ; Tue, 2 May 2023 20:12:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229903AbjEBUMn (ORCPT ); Tue, 2 May 2023 16:12:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229891AbjEBUMh (ORCPT ); Tue, 2 May 2023 16:12:37 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 981AF1FC4 for ; Tue, 2 May 2023 13:12:36 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-55a42c22300so48385527b3.2 for ; Tue, 02 May 2023 13:12:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1683058356; x=1685650356; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=VMIztS2TNwPWi8y+6jVOhYQ7jYaHWdPJl8c/QL2NrEY=; b=vQlQykZ5uh/16XZqfDggy9giUk9u4L5cMszHyutb9jXZOteX3TlrL/HOqx9UkTOLiT p3tRhBkLYOgTRbxTtbLi2Tny2dzCqPk9AHO/ZbislK7TlzxNPJifN4qKVffH5lLCY++D xMClbgbIJLFfFSjHgvZlOAGgPd0tj+Him+dRX/76AV9bcP5WzwGHBhOgfUhq/NDJJNmL 59YF0JvwcNmQ015tapHXY9Q5D7rASjUc5yReEUhP5T78kxhNsvsVkYl12BX/Sy6BgNZu B/2vOtSiHdlhvV6PCCkhGP45QhB4DTmxg6UcMrCueloiYQSGqr7Vm8CUp8t6Cmb+aqar AbLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683058356; x=1685650356; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=VMIztS2TNwPWi8y+6jVOhYQ7jYaHWdPJl8c/QL2NrEY=; b=l6GLI47Hv86vp076eFtkq+E7d0tsmGAKRtY0W3KNxQGIYfKagvf9yeTpicIC0PbWla l2/PbWneJ/NuGNR7MkY1gaVmsKXwsY/RGQQQ+qcLzkZ4kmuWZMvVAm0pbVzP/nZMyBmX HKvc6RiOBkTWDcnzvd2xjdoCpvGuo8Y43Hh0RheDtRkBIt3vkX8ZF9CKkwoX9lDP3/lU 5MO5js/gLa3MtwFyDgsKukvX+whP+A8Wl6h5lLTF/5YA8TvVmib09ndFcoCAugabxP6B +G4xKZ0ackVN/3hX4n2G+/pI03t1lPvQWWA1YcyMltnX5oxxmwZ8RYW+gcnY33CtAPKq 897A== X-Gm-Message-State: AC+VfDzl88zcgh4OdhaT/8GOgcTVqdk+tq+IuL/H29j8r1ok+tqZHpx1 BYT6kbvQtCnSfIA1sXMoehRiClk7Yju6zA== X-Google-Smtp-Source: ACHHUZ5LCvzhAYVMOiqdp21gwJ4dCMIkLjoIb5K22efre2i1f9fvCbNB0ZSEg4gg39aEP4G726g7J4liKCcyTQ== X-Received: from xllamas.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5070]) (user=cmllamas job=sendgmr) by 2002:a81:ac49:0:b0:55a:8e39:57a7 with SMTP id z9-20020a81ac49000000b0055a8e3957a7mr2299204ywj.6.1683058355888; Tue, 02 May 2023 13:12:35 -0700 (PDT) Date: Tue, 2 May 2023 20:12:19 +0000 In-Reply-To: <20230502201220.1756319-1-cmllamas@google.com> Mime-Version: 1.0 References: <20230502201220.1756319-1-cmllamas@google.com> X-Mailer: git-send-email 2.40.1.495.gc816e09b53d-goog Message-ID: <20230502201220.1756319-3-cmllamas@google.com> Subject: [PATCH 3/3] binder: add lockless binder_alloc_(set|get)_vma() From: Carlos Llamas To: Greg Kroah-Hartman , "=?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?=" , Todd Kjos , Martijn Coenen , Joel Fernandes , Christian Brauner , Carlos Llamas , Suren Baghdasaryan , "Liam R. Howlett" , Andrew Morton Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Liam Howlett , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bring back the original lockless design in binder_alloc to determine whether the buffer setup has been completed by the ->mmap() handler. However, this time use smp_load_acquire() and smp_store_release() to wrap all the ordering in a single macro call. Also, add comments to make it evident that binder uses alloc->vma to determine when the binder_alloc has been fully initialized. In these scenarios acquiring the mmap_lock is not required. Fixes: a43cfc87caaf ("android: binder: stop saving a pointer to the VMA") Cc: Liam Howlett Cc: Suren Baghdasaryan Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas --- drivers/android/binder_alloc.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index eb082b33115b..e7c9d466f8e8 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -309,17 +309,18 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, return vma ? -ENOMEM : -ESRCH; } +static inline void binder_alloc_set_vma(struct binder_alloc *alloc, + struct vm_area_struct *vma) +{ + /* pairs with smp_load_acquire in binder_alloc_get_vma() */ + smp_store_release(&alloc->vma, vma); +} + static inline struct vm_area_struct *binder_alloc_get_vma( struct binder_alloc *alloc) { - struct vm_area_struct *vma = NULL; - - if (alloc->vma) { - /* Look at description in binder_alloc_set_vma */ - smp_rmb(); - vma = alloc->vma; - } - return vma; + /* pairs with smp_store_release in binder_alloc_set_vma() */ + return smp_load_acquire(&alloc->vma); } static bool debug_low_async_space_locked(struct binder_alloc *alloc, int pid) @@ -382,6 +383,7 @@ static struct binder_buffer *binder_alloc_new_buf_locked( size_t size, data_offsets_size; int ret; + /* Check binder_alloc is fully initialized */ if (!binder_alloc_get_vma(alloc)) { binder_alloc_debug(BINDER_DEBUG_USER_ERROR, "%d: binder_alloc_buf, no vma\n", @@ -777,7 +779,9 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, buffer->free = 1; binder_insert_free_buffer(alloc, buffer); alloc->free_async_space = alloc->buffer_size / 2; - alloc->vma = vma; + + /* Signal binder_alloc is fully initialized */ + binder_alloc_set_vma(alloc, vma); return 0; @@ -959,7 +963,7 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc) */ void binder_alloc_vma_close(struct binder_alloc *alloc) { - alloc->vma = 0; + binder_alloc_set_vma(alloc, NULL); } /** -- 2.40.1.495.gc816e09b53d-goog