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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2575FF9936B for ; Thu, 23 Apr 2026 10:39:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cGEO2F0ScelrhYb0KLha9yRxuMqwCHKRlDug71W0idc=; b=o1JKW2YKhooDuuN6S8m0Kh+kIo 4MjI/X78Ey30bvvdV0CmsbEG7i1W3yx1CkOSWTTasNUQflYXf9C2Nl4mVea7lUJiu3bVE1jAoq2lW tGb7RVptVxVn6uE6nJy5ykwt1+DBQS4BZ7312JLmCvby7LEmVagASxYENXS19jxQaRrj791T53Okb xxvIOUQOH2rIRsgOJdXdsULsaNgl8dswb2vFYGX1ZTFh7ky1IZP4BuOWvStRWp9ETxBsDB0MBJPdm tdwzArHHvnj7hDoYazRZNZNB0xz7LK6TZcJ7cqUBy9FKWfTKRRRLMRCASN5HmHn8GQuF+5XnG1hMk 5PWzsjyQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wFrTC-0000000BUgj-3zCG; Thu, 23 Apr 2026 10:39:42 +0000 Received: from galois.linutronix.de ([2a0a:51c0:0:12e:550::1]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wFrTA-0000000BUg8-22JM for linux-arm-kernel@lists.infradead.org; Thu, 23 Apr 2026 10:39:41 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1776940777; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=cGEO2F0ScelrhYb0KLha9yRxuMqwCHKRlDug71W0idc=; b=AuW1xLgtZm+C8AnaQKzWFF9ZB1yEB+dmq6Pz4OGcKHDgIWWmYYXSJGGFIdfxk7VyzA+Znm MQtCwuJoUu5RkUE16EMgFycJkQBRJkQXe6IP0y+ewDd3ag329+5l1zkCDJpwebMtt3om/r G0EfMn8H9+BC4sRMaQWQuBNEprFpp3rVgR2wjM/KdPLo/kBaIHHumei7A369z2YjQWlcpm NnZM7hbFPGB6YVoBAvSjgFDa19IWRewfsnmZK19tOsxYrporbOnSFtl1vG/hrIUg9a8e4i HN2jEdG/NYNTUrH/sqg2G6NvMZvP03wAuIawYNA6eG/67A3CXob8UKH8PGHr2Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1776940777; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=cGEO2F0ScelrhYb0KLha9yRxuMqwCHKRlDug71W0idc=; b=HRXq/PfnQegrvLWQuStXBRMN299tx2QwQeuxH8m0oYNyaMoxm4tb4mGPSv/bPhl2C+9y3s 551qIyszJd9b2LCw== To: Dmitry Vyukov , Jinjie Ruan , linux-man@vger.kernel.org Cc: Mark Rutland , Mathias Stearn , Mathieu Desnoyers , Catalin Marinas , Will Deacon , Boqun Feng , "Paul E. McKenney" , Chris Kennelly , regressions@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Peter Zijlstra , Ingo Molnar , Blake Oler Subject: Re: [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64 and tcmalloc everywhere In-Reply-To: References: <87zf2u28d1.ffs@tglx> <87wlxy22x7.ffs@tglx> Date: Thu, 23 Apr 2026 12:39:36 +0200 Message-ID: <87ik9i0xlj.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260423_033940_666562_1ADEAE2F X-CRM114-Status: GOOD ( 10.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Apr 23 2026 at 07:53, Dmitry Vyukov wrote: > On Thu, 23 Apr 2026 at 03:48, Jinjie Ruan wrote: > > This part of the rseq man page needs to be fixed as well I think. The > kernel no longer reliably provides clearing of rseq_cs on preemption, > right? > > https://git.kernel.org/pub/scm/libs/librseq/librseq.git/tree/doc/man/rseq.2#n241 > > "and set to NULL by the kernel when it restarts an assembly > instruction sequence block, > as well as when the kernel detects that it is preempting or delivering > a signal outside of the range targeted by the rseq_cs." The kernel clears rseq_cs reliably when user space was interrupted and: the task was preempted or the return from interrupt delivers a signal If the task invoked a syscall then there is absolutely no reason to do either of this because syscalls from within a critical section are a bug and catched when enabling rseq debugging. The original code did this along with unconditionally updating CPU/MMCID which resulted in ~15% performance regression on a syscall heavy database benchmark once glibc started to register rseq. Thanks, tglx