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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 AFACAC43603 for ; Tue, 10 Dec 2019 22:33:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8411C2077B for ; Tue, 10 Dec 2019 22:33:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="LFKPWlTe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728527AbfLJWdE (ORCPT ); Tue, 10 Dec 2019 17:33:04 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:34275 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729403AbfLJWcV (ORCPT ); Tue, 10 Dec 2019 17:32:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576017140; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DIEGxaEoEqnxv3W7KxXHjyimH36onDwUaRqX3wb5gSo=; b=LFKPWlTe7u6TnMA7crp/fd/4aiJ6lABRNz3CfHQO7vGoSvMHROXZaTlt7fUCFNRIJWQBnl kTX0p9cvoKpn0QvzUotLrYME9LN5OTUrYPnHoq6Y/RcLT6d57rZjAScvJtBBRs9aOREd// /+GIhzqx3RljqJKr8FZrajFGZWE/6AQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-205-CRXAWaLROYCkocpE2NuCbA-1; Tue, 10 Dec 2019 17:32:16 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 426DD800D41; Tue, 10 Dec 2019 22:32:15 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-250.rdu2.redhat.com [10.10.120.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 818A45D9C5; Tue, 10 Dec 2019 22:32:13 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20191210220523.28540-1-dave@stgolabs.net> References: <20191210220523.28540-1-dave@stgolabs.net> <20191210193011.GA11802@worktop.programming.kicks-ass.net> To: Davidlohr Bueso Cc: dhowells@redhat.com, peterz@infradead.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, will@kernel.org, Davidlohr Bueso Subject: Re: [PATCH] Revert "locking/mutex: Complain upon mutex API misuse in IRQ contexts" MIME-Version: 1.0 Content-ID: <24324.1576017132.1@warthog.procyon.org.uk> Date: Tue, 10 Dec 2019 22:32:12 +0000 Message-ID: <24325.1576017132@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: CRXAWaLROYCkocpE2NuCbA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Davidlohr Bueso wrote: > This ended up causing some noise in places such as rxrpc running in softi= rq. >=20 > The warning is misleading in this case as the mutex trylock and unlock > operations are done within the same context; and therefore we need not > worry about the PI-boosting issues that comes along with no single-owner > lock guarantees. >=20 > While we don't want to support this in mutexes, there is no way out of > this yet; so lets get rid of the WARNs for now, as it is only fair to > code that has historically relied on non-preemptible softirq guarantees. > In addition, changing the lock type is also unviable: exclusive rwsems > have the same issue (just not the WARN_ON) and counting semaphores > would introduce a performance hit as mutexes are a lot more optimized. >=20 > This reverts commit 5d4ebaa87329ef226e74e52c80ac1c62e4948987. >=20 > Signed-off-by: Davidlohr Bueso Tested-by: David Howells