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 884ADC7618E for ; Mon, 24 Apr 2023 20:56:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232270AbjDXU4j (ORCPT ); Mon, 24 Apr 2023 16:56:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52754 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232396AbjDXU4e (ORCPT ); Mon, 24 Apr 2023 16:56:34 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDFD172BC for ; Mon, 24 Apr 2023 13:56:30 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-b92309d84c1so23438461276.1 for ; Mon, 24 Apr 2023 13:56:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1682369790; x=1684961790; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=QAxnpNVVBFuzE9GYOOg2/Ftab/EjG3MWY6IMj4Qumjs=; b=ujb5zcd1KBzxKAOR4hk1uqxutbd1kanM+csJA1meOHmJYxrDHyXEUf3s3F1CNaMMTY F2UwG5dJWdwrPjS2m5St4fIIHRJgNJiv0eMCV6hQxhsfJ1N8OaV3vbFI+A7C3y1gHu+y g0M22QeG0lUyYp4TXj6vtk5ieXBXEvHzRFXWxXxCWmZCBUyzVZZz+uPZfQ1GzE18UOXY 4M+ZzEilfIiNrA+1l4QqmYZZEjKLkiQH7TBNlsxSgN7UG/arCZzAtq+ArTot61JKzNGT uDp4x5XHVNY6pLU5J2Ri8EtTP4pSnmqQVeQFLhwuYrSz4MJtzFS+UQa7ewmDeHz8iBWN Z39Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682369790; x=1684961790; 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=QAxnpNVVBFuzE9GYOOg2/Ftab/EjG3MWY6IMj4Qumjs=; b=YEUyWGl1rdqbZizzeD1agag2f32gfFL/9NXsgJ5mzf98lyIw8kD5GlKry6UeDjso0h 1yqSBYocCEsVQpMbZ29dtT45Nashjd3oKIgevBQ23E8OP1UBYYwp1htDTS10oBa0Yhq/ r+9MEYMITPbI4RzNiloUTRjnMyANq+1tKekvlBXJONfxtnhSDmjxU0pWnvumC6CRkQJY Azp/gIymlKaMo/5vVHjGJKKgjvGjwUVfaRs0doMaQeJwIyrQxCwHRTSt5/KgVue5N9vQ vm8lNCpBasTnBPQUjNl3dVh3vVtw1c4eJUXEvElS/4I7FcMfq07tDxWz5KobKUE/sFw8 SqLA== X-Gm-Message-State: AAQBX9c0kmGUQBnqBZ2AoRuqba1jFsp13GwQeoBPwZGer+SoAJ4cRjWc 8rwnUsdYHiyXwf1QaymTwXCkHX1AOVxlKQ== X-Google-Smtp-Source: AKy350YYjyTgO+6IXh8tE7lK5L05UhrxABixhGBxviWUwc34wdRKdakSngp8Can2PQClrrENEQ1oz1U4wvGx7A== X-Received: from xllamas.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5070]) (user=cmllamas job=sendgmr) by 2002:a25:cc16:0:b0:b8e:efd8:f2c with SMTP id l22-20020a25cc16000000b00b8eefd80f2cmr8406994ybf.1.1682369790208; Mon, 24 Apr 2023 13:56:30 -0700 (PDT) Date: Mon, 24 Apr 2023 20:55:48 +0000 In-Reply-To: <20230424205548.1935192-1-cmllamas@google.com> Mime-Version: 1.0 References: <20230424205548.1935192-1-cmllamas@google.com> X-Mailer: git-send-email 2.40.0.634.g4ca3ef3211-goog Message-ID: <20230424205548.1935192-3-cmllamas@google.com> Subject: [RFC 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 Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Liam Howlett 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. Cc: Liam Howlett Cc: Suren Baghdasaryan Signed-off-by: Carlos Llamas --- drivers/android/binder_alloc.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index eb082b33115b..9d166e10315e 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -309,17 +309,16 @@ 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) +{ + 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; + return smp_load_acquire(&alloc->vma); } static bool debug_low_async_space_locked(struct binder_alloc *alloc, int pid) @@ -382,6 +381,7 @@ 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 +777,9 @@ 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 +961,7 @@ 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); } /** -- 2.40.0.634.g4ca3ef3211-goog