From patchwork Tue Feb 2 13:38:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 375263 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6077EC4332B for ; Tue, 2 Feb 2021 14:13:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 306A864F51 for ; Tue, 2 Feb 2021 14:13:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234174AbhBBOMs (ORCPT ); Tue, 2 Feb 2021 09:12:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:49664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234032AbhBBOLj (ORCPT ); Tue, 2 Feb 2021 09:11:39 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 503AC64F51; Tue, 2 Feb 2021 13:51:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612273891; bh=nj40X3oc1G/FiWH8ruxoXEkmhYb4f2qFzBnxrS93xZw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rRkX9X5eqApntcLAF+rmUCaf4wl46DRj4V/HsVpWI41gjPkrDhMIaSPq3vUcsapTQ +YUcmi1ubNGXlVY038eg9mpXLUFz46MB416e3OctyQqrrhGU6zsEhMWUmJ+PaBc+ph pFoLYYC6hIk3yOAHNSg+POLMbyk0maAbeQeUwRuI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Thomas Gleixner , Ingo Molnar , "Peter Zijlstra (Intel)" , Lee Jones Subject: [PATCH 4.9 14/32] futex: Provide distinct return value when owner is exiting Date: Tue, 2 Feb 2021 14:38:37 +0100 Message-Id: <20210202132942.589673030@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202132942.035179752@linuxfoundation.org> References: <20210202132942.035179752@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Thomas Gleixner commit ac31c7ff8624409ba3c4901df9237a616c187a5d upstream. attach_to_pi_owner() returns -EAGAIN for various cases: - Owner task is exiting - Futex value has changed The caller drops the held locks (hash bucket, mmap_sem) and retries the operation. In case of the owner task exiting this can result in a live lock. As a preparatory step for seperating those cases, provide a distinct return value (EBUSY) for the owner exiting case. No functional change. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20191106224556.935606117@linutronix.de Signed-off-by: Greg Kroah-Hartman Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1918,12 +1918,13 @@ retry_private: if (!ret) goto retry; goto out; + case -EBUSY: case -EAGAIN: /* * Two reasons for this: - * - Owner is exiting and we just wait for the + * - EBUSY: Owner is exiting and we just wait for the * exit to complete. - * - The user space value changed. + * - EAGAIN: The user space value changed. */ double_unlock_hb(hb1, hb2); hb_waiters_dec(hb2); @@ -2615,12 +2616,13 @@ retry_private: goto out_unlock_put_key; case -EFAULT: goto uaddr_faulted; + case -EBUSY: case -EAGAIN: /* * Two reasons for this: - * - Task is exiting and we just wait for the + * - EBUSY: Task is exiting and we just wait for the * exit to complete. - * - The user space value changed. + * - EAGAIN: The user space value changed. */ queue_unlock(hb); put_futex_key(&q.key);