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 2543CFED3FA for ; Fri, 24 Apr 2026 19:44:31 +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=2+rliU4cCrurJTfrKWYSNMc97AT2PbQ8kt0LrYzMJys=; b=HJutWqnyCY1lOMTA5EpePohHY5 yOPoiEekeQl4gTAKV/2B5tOtUk4IefMuoO08c0rlhtV6nl8t/v3hhAtzRP5B7zlXisM5GYVMqyjDp xhmg6rFIsU8NEEEiqfwt8DoFdL8yKjAXK07W/Pn4CFQxPIHOc4rWwZbAOouc9P3IdT5xHEdAbldBi JZreZ8a6ApwlUeFrlhcz5bNijXWuGPMT4ZOuxJ7xY1xb3SybcWHRi/h43AM0kfrrjxTgIcOpqB7QI hirZCmPr21VIfmVotRW1cK7eMn6Jhcnhnel59Wn+B+p/YuQ6zThMKohChNnZ3KNMR4S62i4M1qLvm PwZE/J5w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wGMRt-0000000Di7W-27Bu; Fri, 24 Apr 2026 19:44:25 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wGMRq-0000000Di7A-1ip0 for linux-arm-kernel@lists.infradead.org; Fri, 24 Apr 2026 19:44:23 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1777059857; 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=2+rliU4cCrurJTfrKWYSNMc97AT2PbQ8kt0LrYzMJys=; b=4RH1XcFRCUI4pUKFbbaE2ynLn8NOaT602kfQD31J3RDvJfJo7XD92FNpJWLLlcewr0T0mx vN065gMMtlaUbKpjo3gXmlXENzp23fTKmDuJxX9zay6l/eNhSStIrom9wHBQBfbpJhHUA1 n1WNq9N84pxe7o/+aHeImeRSB/w6hav2SbDOfsSgxSIfr/h2nypcGrNEJ6dmcmcKyN/V6z rijeVmFkNDQY6InHkE5L5GhmFG5i2y1E9RO2nJwnNqaelod8gOb4/N9/+AJiTaWHK5f013 w/eRZCDT3NHFxYWTwvBUMPhyE9BD8eLGG77wcpWUwsrikwt4aL2/Kd6ACssj7g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1777059857; 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=2+rliU4cCrurJTfrKWYSNMc97AT2PbQ8kt0LrYzMJys=; b=iqLfAh0zDX4+KsEUDE175S10unwiIU8nPBL256ZhVyzK9+tvLFrNWGmxv0kvMxKW1j2tRu GSek67fxRGEDh5BQ== To: Peter Zijlstra Cc: Mathias Stearn , Dmitry Vyukov , Jinjie Ruan , linux-man@vger.kernel.org, Mark Rutland , 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, Ingo Molnar , Blake Oler Subject: Re: [REGRESSION] rseq: refactoring in v6.19 broke everyone on arm64 and tcmalloc everywhere In-Reply-To: <20260424150318.GE641209@noisy.programming.kicks-ass.net> References: <87wlxy22x7.ffs@tglx> <87ik9i0xlj.ffs@tglx> <87a4ut1njh.ffs@tglx> <87v7dgzbo7.ffs@tglx> <20260424150318.GE641209@noisy.programming.kicks-ass.net> Date: Fri, 24 Apr 2026 21:44:16 +0200 Message-ID: <87se8kywhb.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-20260424_124422_591568_CC95A852 X-CRM114-Status: UNSURE ( 9.74 ) X-CRM114-Notice: Please train this message. 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 Fri, Apr 24 2026 at 17:03, Peter Zijlstra wrote: > On Fri, Apr 24, 2026 at 04:16:08PM +0200, Thomas Gleixner wrote: >> > I was really hoping that we would only need to do the "redundant" >> > cpu_id_start writes would only be needed on membarrier_rseq IPIs where >> > it really is a pay-for-what-you-use functionality, >> >> That's fine and can be solved without adding this sequence overhead into >> the scheduler hotpath. > > Something like so? (probably needs help for !GENERIC bits) Yes and yes :) Let me stare at that !generic tif bits case.