From nobody Sun Apr 12 05:51:30 2026 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 ED188C00144 for ; Mon, 1 Aug 2022 13:25:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231290AbiHANZ6 (ORCPT ); Mon, 1 Aug 2022 09:25:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231496AbiHANZn (ORCPT ); Mon, 1 Aug 2022 09:25:43 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79D4739B94; Mon, 1 Aug 2022 06:25:42 -0700 (PDT) Date: Mon, 01 Aug 2022 13:25:39 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1659360341; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sHXy2YTofn+Ct+amiEKkOUOnH9OzAMcdg5/V6z2J7CM=; b=p23dA/z+WQIum3kOXmP55zCS139Fh5veWQzNK3EiDAN0blqpo6pC3DIdlqXpmVgAqVf1vF eghEqbReyehaAO3sJK/dGpj5W594H2l767oHOIEmO5a6UGuOj5tXxVn7B8q1v3fGHKBHD+ QzWuBVIDc1YstNRvDz2ETqSdstOrkI6zIjwyOBYtO/ZEckHMJO7DjK8/rU7865LE+JAe52 oJirlSXZO5TnXtmXPk0ro3VXL5A8Upzsz1X+XtkhZG6G7iFz0MflL7zUTZXzvmU5XplupW 01SxFSx+Jm5nRkNgsqnznGv8/t/KQdNPPqzSo7ZqflJfHpTW+LzEA6cfA/t0Ag== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1659360341; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sHXy2YTofn+Ct+amiEKkOUOnH9OzAMcdg5/V6z2J7CM=; b=8fOVn3n4bGOH5YkK74kus9Tay8+rgw0ttxfe3xmvVAqMBchHr32vPc+TnJnU5gOwtiFyDX vt/SlwRtujmXwCCQ== From: "tip-bot2 for Mathieu Desnoyers" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags Cc: Mathieu Desnoyers , "Peter Zijlstra (Intel)" , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220622194617.1155957-1-mathieu.desnoyers@efficios.com> References: <20220622194617.1155957-1-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Message-ID: <165936033979.15455.14072233165429721291.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 0190e4198e47fe99d002d72588f34fd62c9ab570 Gitweb: https://git.kernel.org/tip/0190e4198e47fe99d002d72588f34fd62= c9ab570 Author: Mathieu Desnoyers AuthorDate: Wed, 22 Jun 2022 15:46:16 -04:00 Committer: Ingo Molnar CommitterDate: Mon, 01 Aug 2022 15:21:29 +02:00 rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags The pretty much unused RSEQ_CS_FLAG_NO_RESTART_ON_* flags introduce complexity in rseq, and are subtly buggy [1]. Solving those issues requires introducing additional complexity in the rseq implementation for each supported architecture. Considering that it complexifies the rseq ABI, I am proposing that we deprecate those flags. [2] So far there appears to be consensus from maintainers of user-space projects impacted by this feature that its removal would be a welcome simplification. [3] The deprecation approach proposed here is to issue WARN_ON_ONCE() when encountering those flags and kill the offending process with sigsegv. This should allow us to quickly identify whether anyone yells at us for removing this. Link: https://lore.kernel.org/lkml/20220618182515.95831-1-minhquangbui99@gm= ail.com/ [1] Link: https://lore.kernel.org/lkml/258546133.12151.1655739550814.JavaMail.z= imbra@efficios.com/ [2] Link: https://lore.kernel.org/lkml/87pmj1enjh.fsf@email.froward.int.ebieder= m.org/ [3] Signed-off-by: Mathieu Desnoyers Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/lkml/20220622194617.1155957-1-mathieu.desnoye= rs@efficios.com --- kernel/rseq.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/kernel/rseq.c b/kernel/rseq.c index 97ac20b..81d7dc8 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -18,8 +18,9 @@ #define CREATE_TRACE_POINTS #include =20 -#define RSEQ_CS_PREEMPT_MIGRATE_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE = | \ - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT) +#define RSEQ_CS_NO_RESTART_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT | \ + RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL | \ + RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE) =20 /* * @@ -175,23 +176,15 @@ static int rseq_need_restart(struct task_struct *t, u= 32 cs_flags) u32 flags, event_mask; int ret; =20 + if (WARN_ON_ONCE(cs_flags & RSEQ_CS_NO_RESTART_FLAGS)) + return -EINVAL; + /* Get thread flags. */ ret =3D get_user(flags, &t->rseq->flags); if (ret) return ret; =20 - /* Take critical section flags into account. */ - flags |=3D cs_flags; - - /* - * Restart on signal can only be inhibited when restart on - * preempt and restart on migrate are inhibited too. Otherwise, - * a preempted signal handler could fail to restart the prior - * execution context on sigreturn. - */ - if (unlikely((flags & RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL) && - (flags & RSEQ_CS_PREEMPT_MIGRATE_FLAGS) !=3D - RSEQ_CS_PREEMPT_MIGRATE_FLAGS)) + if (WARN_ON_ONCE(flags & RSEQ_CS_NO_RESTART_FLAGS)) return -EINVAL; =20 /* @@ -203,7 +196,7 @@ static int rseq_need_restart(struct task_struct *t, u32= cs_flags) t->rseq_event_mask =3D 0; preempt_enable(); =20 - return !!(event_mask & ~flags); + return !!event_mask; } =20 static int clear_rseq_cs(struct task_struct *t)