From patchwork Tue Oct 11 20:55:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Desaulniers X-Patchwork-Id: 13004331 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 36154C4332F for ; Tue, 11 Oct 2022 20:56:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229508AbiJKU4D (ORCPT ); Tue, 11 Oct 2022 16:56:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229452AbiJKU4B (ORCPT ); Tue, 11 Oct 2022 16:56:01 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDEA058DEB for ; Tue, 11 Oct 2022 13:56:00 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id p5-20020a25bd45000000b006beafa0d110so14361736ybm.1 for ; Tue, 11 Oct 2022 13:56:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=xYxJs2vRth6XEldvpd7cCs72Yhted4rknZIaH3l0kX4=; b=TuUPF111ikwTGiQiA1pvT8abbak3tcqv/wR29Z1fj7pKh1P7MvVH2Zd+0g78s0t7AL VgBafkzWaczA/kbcKtASceofDWzHEKret+UfCmury9gZ9C0cwnRytdAwonUuht3QseYx fmPk+w5ufFKv9d3tXJ0DfikUNsXsVsnrLcL0b023Uzyd3YZD+qPwNRWDWpIrnl1jdiSv ZwDDotGgKixWZ6rzcpaX+aoQHzRpSPytzEj5Vw7TVjif3mK36haJTtYLlLhKamfG8zIS cKrO6ATcExQLMn1+PuZcKp9Vw0Lw0r5KbEthrZoxexVlCsEwLRaiNUzuxLmaN0/f5DQI nomg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=xYxJs2vRth6XEldvpd7cCs72Yhted4rknZIaH3l0kX4=; b=sOH8/+UE9kULhliG8WfXvTQnq+HWkeUbDymOhYxy7hixIf9QZ245N94IBSOpSAZtYs cmFNTPp1RBDFtq+DAQatSmgnblWR0CXNm499/wIkDZS3OA2G7k2pTeKwnI+sK2FHjjmf lKSeydCvKvf+6bBTc5Wts7OicbeEb4beKT8YoV++mXfFkEiFVI0VynropVsOgRzSjXOI e/TB4ztMroBXyxaAvP2Apfr3r7W0Z52nvnAS7gVg2VKmIHidkXxgZ1ch2q/fRLrhaUDJ YRxZV36TO223q+89F8YWAfpg1BizkbjwWfsgJgDpyLv8EDxSrYVMZIkOTwmcD6IJrPs1 VNGw== X-Gm-Message-State: ACrzQf2zlmaGEb8wd9tOsavQEr0MLJFmElJH8tShom285Geptzbiovem ZqU32YgFhbLGkY115yErmV0kfD/iGDJBEeAVgvU= X-Google-Smtp-Source: AMsMyM44+ntM8yviuIiZd5PKWLhSqxXCty8/o0mGlNcfuIBxiQ8sWjXRRjlkrJ1CNPB2WgZ9p8UgzDXvtSKDrjMNU3c= X-Received: from ndesaulniers-desktop.svl.corp.google.com ([2620:0:100e:712:4ed2:3edd:ee48:33e0]) (user=ndesaulniers job=sendgmr) by 2002:a81:844f:0:b0:356:9481:8792 with SMTP id u76-20020a81844f000000b0035694818792mr24950381ywf.138.1665521760039; Tue, 11 Oct 2022 13:56:00 -0700 (PDT) Date: Tue, 11 Oct 2022 13:55:47 -0700 In-Reply-To: Mime-Version: 1.0 References: X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=UIrHvErwpgNbhCkRZAYSX0CFd/XFEwqX3D0xqtqjNug= X-Developer-Signature: v=1; a=ed25519-sha256; t=1665521747; l=3390; i=ndesaulniers@google.com; s=20220923; h=from:subject; bh=X+cvnL0/9tWxHyPq7VqQPGifcP15h1D7GusdoDV01Dc=; b=CZMzazlI/uts3rfQLikQnvuAXx1USm8fEHeveny4RE2lc4TgnvaA/U/CgBI03pAmME3GBnCfpqE/ 8SdrJm7jBd8WA+xub5iAXZc8sLRfqYF+fPqzy+U2qQFkSXV9sBYM X-Mailer: git-send-email 2.38.0.rc2.412.g84df46c1b4-goog Message-ID: <20221011205547.14553-1-ndesaulniers@google.com> Subject: [PATCH v2] fs/select: mark do_select noinline_for_stack From: Nick Desaulniers To: Andrew Morton , Arnd Bergmann Cc: Alexander Viro , Nathan Chancellor , Tom Rix , Xiaoming Ni , Luis Chamberlain , Andi Kleen , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Christoph Hellwig , Eric Dumazet , "Darrick J. Wong" , Greg Kroah-Hartman , Nick Desaulniers Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Effectively a revert of commit ad312f95d41c ("fs/select: avoid clang stack usage warning") Various configs can still push the stack useage of core_sys_select() over the CONFIG_FRAME_WARN threshold (1024B on 32b targets). fs/select.c:619:5: error: stack frame size of 1048 bytes in function 'core_sys_select' [-Werror,-Wframe-larger-than=] core_sys_select() has a large stack allocation for `stack_fds` where it tries to do something equivalent to "small string optimization" to potentially avoid a kmalloc. core_sys_select() calls do_select() which has another potentially large stack allocation, `table`. Both of these values depend on FRONTEND_STACK_ALLOC. Mix those two large allocation with register spills which are exacerbated by various configs and compiler versions and we can just barely exceed the 1024B limit. Rather than keep trying to find the right value of MAX_STACK_ALLOC or FRONTEND_STACK_ALLOC, mark do_select() as noinline_for_stack. The intent of FRONTEND_STACK_ALLOC is to help potentially avoid a dynamic memory allocation. In that spirit, restore the previous threshold but separate the stack frames. Many tests of various configs for different architectures and various versions of GCC were performed; do_select() was never inlined into core_sys_select() or compat_core_sys_select(). The kernel is built with the GCC specific flag `-fconserve-stack` which can limit inlining depending on per-target thresholds of callee stack size, which helps avoid the issue when using GCC. Clang is being more aggressive and not considering the stack size when decided whether to inline or not. We may consider using the clang-16+ flag `-finline-max-stacksize=` in the future. Link: https://lore.kernel.org/lkml/20221006222124.aabaemy7ofop7ccz@google.com/ Fixes: ad312f95d41c ("fs/select: avoid clang stack usage warning") Suggested-by: Arnd Bergmann Signed-off-by: Nick Desaulniers Tested-by: Nathan Chancellor --- Changes v1 -> v2: * Drop the 32b specific guard, since I could reproduce the no-inlining w/ aarch64-linux-gnu-gcc-10 ARCH=arm64 defconfig, and per Arnd. * Drop references to 32b in commit message. * Add new paragraph in commit message at the end about -fconserve-stack and -finline-max-stacksize=. * s/malloc/kmalloc/ in commit message. fs/select.c | 1 + include/linux/poll.h | 4 ---- 2 files changed, 1 insertion(+), 4 deletions(-) diff --git a/fs/select.c b/fs/select.c index 0ee55af1a55c..794e2a91b1fa 100644 --- a/fs/select.c +++ b/fs/select.c @@ -476,6 +476,7 @@ static inline void wait_key_set(poll_table *wait, unsigned long in, wait->_key |= POLLOUT_SET; } +noinline_for_stack static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time) { ktime_t expire, *to = NULL; diff --git a/include/linux/poll.h b/include/linux/poll.h index a9e0e1c2d1f2..d1ea4f3714a8 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -14,11 +14,7 @@ /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating additional memory. */ -#ifdef __clang__ -#define MAX_STACK_ALLOC 768 -#else #define MAX_STACK_ALLOC 832 -#endif #define FRONTEND_STACK_ALLOC 256 #define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC #define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC