From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1525702546; cv=none; d=google.com; s=arc-20160816; b=k8FWG4dLCaHQXx3N/49cJ2yCX7abAHq4nAzDjOsgoLub1PgtKnMghdPhCSYG/7Sv+t F7uGLhY8jBc8xVY0pOGJYjvCiD7ZvJv65PtOUEKlc4YxWeqLYwGBPjViQBXMmLMwBkSt xyvd9pdxL0eJVF6GJGubybt0dJPDHnaaFwPgRe1cPLvrtA4n1iHcd8XPBKwsx8o4ZVfz g9dJM+QogpV3zAzwSpJ0NMdHDJWKXc+PwUsnvncc/ORe2GG+BoKjJAEJASOcIekziL77 CkOqGvXESoLcF+O0PccQa0do5SAbkARXL7uXX0h8s5c/d2qOO3sdUBXrj8k3kjchNTU1 4pqA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:sender:dkim-signature:arc-authentication-results; bh=A8za/HAl2IiLicvYE/2KOWhqmHyqEzVAnVWz7lYvwto=; b=rUSGvXcLkaevWbzkVEeW3Hd6JWV16xK02QDJWpjM5jkSSD0EhcJBqAeARk6B7B1JUs UHfiD2x/T0dwHsdiuTmPSeEZDIOg7MW/Cv47/hc5epR9GNIvoIonJzrU4beRwDW7+GPP wvC8XDWyGLNlx/EWfTSb5AqezFSNfipU/a27voSxkMSxy8et5NZyPAx+j+92rS3eMHYG 82Le2ZlMIPr+vBoD0IYZB0/myh+ecZUR/mSFzlQAxniCWBODzBjk6FCX3Ba/5ymcv/5A Xh+8DVtRD77Qrc4COqf6zQxLDS7/FY0qWaNKnDlXGlrWJ4ZEsBWnsm8act+Jfx8Dicd7 QHCg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=bhB/NEn8; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=bhB/NEn8; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Google-Smtp-Source: AB8JxZrInYWV3192pHeDCCc/dTRmQupY8OCyxwj4OqkOrc+ZQGtt48lgeLirPMPnJml41eGuBwMQ+g== Sender: Minchan Kim From: Minchan Kim To: LKML Cc: Minchan Kim , Ganesh Mahendran , Joe Perches , =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Todd Kjos , Greg Kroah-Hartman , Martijn Coenen Subject: [PATCH v6] ANDROID: binder: change down_write to down_read Date: Mon, 7 May 2018 23:15:37 +0900 Message-Id: <20180507141537.4855-1-minchan@kernel.org> X-Mailer: git-send-email 2.17.0.441.gb46fe60e1d-goog MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1599815073448562806?= X-GMAIL-MSGID: =?utf-8?q?1599815073448562806?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: binder_update_page_range needs down_write of mmap_sem because vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless it is set. However, when I profile binder working, it seems every binder buffers should be mapped in advance by binder_mmap. It means we could set VM_MIXEDMAP in binder_mmap time which is already hold a mmap_sem as down_write so binder_update_page_range doesn't need to hold a mmap_sem as down_write. Please use proper API down_read. It would help mmap_sem contention problem as well as fixing down_write abuse. Ganesh Mahendran tested app launching and binder throughput test and he said he couldn't find any problem and I did binder latency test per Greg KH request(Thanks Martijn to teach me how I can do) I cannot find any problem, too. Cc: Ganesh Mahendran Cc: Joe Perches Cc: Arve Hjønnevåg Cc: Todd Kjos Reviewed-by: Martijn Coenen Signed-off-by: Minchan Kim Reviewed-by: Joel Fernandes (Google) --- drivers/android/binder.c | 4 +++- drivers/android/binder_alloc.c | 6 +++--- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 4eab5be3d00f..7b8e96f60719 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -4730,7 +4730,9 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma) failure_string = "bad vm_flags"; goto err_bad_arg; } - vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE; + vma->vm_flags |= VM_DONTCOPY | VM_MIXEDMAP; + vma->vm_flags &= ~VM_MAYWRITE; + vma->vm_ops = &binder_vm_ops; vma->vm_private_data = proc; diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 5a426c877dfb..4f382d51def1 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, mm = alloc->vma_vm_mm; if (mm) { - down_write(&mm->mmap_sem); + down_read(&mm->mmap_sem); vma = alloc->vma; } @@ -288,7 +288,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, /* vm_insert_page does not seem to increment the refcount */ } if (mm) { - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } return 0; @@ -321,7 +321,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, } err_no_vma: if (mm) { - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } return vma ? -ENOMEM : -ESRCH; -- 2.17.0.441.gb46fe60e1d-goog