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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 0B831C38A2A for ; Wed, 6 May 2020 21:16:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D79A92075A for ; Wed, 6 May 2020 21:16:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Lzkk0XPi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729876AbgEFVQG (ORCPT ); Wed, 6 May 2020 17:16:06 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:50440 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730010AbgEFVQC (ORCPT ); Wed, 6 May 2020 17:16:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588799760; 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=7DyNQyHWzxz6uGwnYuDMaMxKcoBgqV2azBIQN2WlEbE=; b=Lzkk0XPiz/rIXY4mx8nYhnQW8pyi26qpHoaa0SQPPc/BeUO94nhrTXSXtKx3Pk18IO0H9L b2YDMyghovFz1V4akvz85RAyctfe6M4N4tE79YoFh1UNK4OPOH/wbdRNFOO+8X0SRaV9Kf m/THqYpyonKQjgM+UoEoy8ed9wvH4Gg= 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-368-4EyUww1uN9-HEr2kbOQ9Eg-1; Wed, 06 May 2020 17:15:56 -0400 X-MC-Unique: 4EyUww1uN9-HEr2kbOQ9Eg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 854D1A0BD8; Wed, 6 May 2020 21:15:54 +0000 (UTC) Received: from treble (ovpn-115-96.rdu2.redhat.com [10.10.115.96]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B71E4707A5; Wed, 6 May 2020 21:15:49 +0000 (UTC) Date: Wed, 6 May 2020 16:15:47 -0500 From: Josh Poimboeuf To: Peter Zijlstra Cc: x86@kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, pbonzini@redhat.com, mathieu.desnoyers@efficios.com Subject: Re: [PATCH v4 16/18] static_call: Allow early init Message-ID: <20200506211547.2vnuhkfzhgbi27dm@treble> References: <20200501202849.647891881@infradead.org> <20200501202944.706674211@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200501202944.706674211@infradead.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 01, 2020 at 10:29:05PM +0200, Peter Zijlstra wrote: > In order to use static_call() to wire up x86_pmu, we need to > initialize earlier; copy some of the tricks from jump_label to enable > this. > > Primarily we overload key->next to store a sites pointer when there > are no modules, this avoids having to use kmalloc() to initialize the > sites and allows us to run much earlier. > > (arguably, this is much much earlier than needed for perf, but it > might allow other uses.) > > Signed-off-by: Peter Zijlstra (Intel) > --- > arch/x86/kernel/setup.c | 2 + > arch/x86/kernel/static_call.c | 8 +++++- > include/linux/static_call.h | 15 ++++++++++-- > kernel/static_call.c | 52 +++++++++++++++++++++++++++++++++++++++--- > 4 files changed, 71 insertions(+), 6 deletions(-) This doesn't work when the key is defined in a module. In __static_call_update(), first.site_mod->mod is NULL, but static_call_key_sites() points to the module's call sites. This seems to fix it (sorry, also has the 'next' -> 'mods' rename). The actual fix is in static_call_key_sites() and static_call_key_mods(). diff --git a/include/linux/static_call.h b/include/linux/static_call.h index e112553cfce6..ee55075707f1 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -110,9 +110,10 @@ struct static_call_mod { struct static_call_key { void *func; union { - /* bit0 => 0 - next, 1 - sites */ + /* bit 0: 0 = mods; 1 = sites */ unsigned long type; - struct static_call_mod *next; + + struct static_call_mod *mods; struct static_call_site *sites; }; }; diff --git a/kernel/static_call.c b/kernel/static_call.c index 783953db28c4..d78e50c5b8a3 100644 --- a/kernel/static_call.c +++ b/kernel/static_call.c @@ -94,23 +94,23 @@ static inline void static_call_sort_entries(struct static_call_site *start, static_call_site_cmp, static_call_site_swap); } -static inline bool static_call_key_has_next(struct static_call_key *key) +static inline bool static_call_key_has_mods(struct static_call_key *key) { return !(key->type & 1); } -static inline struct static_call_mod *static_call_key_next(struct static_call_key *key) +static inline struct static_call_mod *static_call_key_mods(struct static_call_key *key) { - if (static_call_key_has_next(key)) - return key->next->next; + if (!static_call_key_has_mods(key)) + return NULL; - return NULL; + return key->mods; } static inline struct static_call_site *static_call_key_sites(struct static_call_key *key) { - if (static_call_key_has_next(key)) - return key->next->sites; + if (static_call_key_has_mods(key)) + return NULL; return (struct static_call_site *)(key->type & ~1); } @@ -118,7 +118,12 @@ static inline struct static_call_site *static_call_key_sites(struct static_call_ void __static_call_update(struct static_call_key *key, void *tramp, void *func) { struct static_call_site *site, *stop; - struct static_call_mod *site_mod, first; + struct static_call_mod *site_mod; + struct static_call_mod first = { + .next = static_call_key_mods(key), + .mod = NULL, + .sites = static_call_key_sites(key), + }; cpus_read_lock(); static_call_lock(); @@ -137,17 +142,14 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func) if (WARN_ON_ONCE(!static_call_initialized)) goto done; - first = (struct static_call_mod){ - .next = static_call_key_next(key), - .mod = NULL, - .sites = static_call_key_sites(key), - }; - for (site_mod = &first; site_mod; site_mod = site_mod->next) { if (!site_mod->sites) { /* * This can happen if the static call key is defined in * a module which doesn't use it. + * + * It also happens in the has_mods case, where the + * 'first' entry has no sites associated with it. */ continue; } @@ -228,12 +230,12 @@ static int __static_call_init(struct module *mod, if (!site_mod) return -ENOMEM; - if (!static_call_key_has_next(key)) { + if (!static_call_key_has_mods(key)) { site_mod->mod = NULL; site_mod->next = NULL; site_mod->sites = static_call_key_sites(key); - key->next = site_mod; + key->mods = site_mod; site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL); if (!site_mod) @@ -242,8 +244,8 @@ static int __static_call_init(struct module *mod, site_mod->mod = mod; site_mod->sites = site; - site_mod->next = key->next; - key->next = site_mod; + site_mod->next = key->mods; + key->mods = site_mod; } do_transform: @@ -328,7 +330,7 @@ static void static_call_del_module(struct module *mod) prev_key = key; - for (prev = &key->next, site_mod = key->next; + for (prev = &key->mods, site_mod = key->mods; site_mod && site_mod->mod != mod; prev = &site_mod->next, site_mod = site_mod->next) ;