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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5BA0EC25B6C for ; Tue, 24 Oct 2023 12:56:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234424AbjJXM4x (ORCPT ); Tue, 24 Oct 2023 08:56:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234204AbjJXM4v (ORCPT ); Tue, 24 Oct 2023 08:56:51 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D390610C0 for ; Tue, 24 Oct 2023 05:56:48 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1698152207; 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=0k8EHTgBuYIMb5TY+j+PPtTNGdHZXI6Ls9DQ9MAsNmk=; b=rLBcBr8dvCVZuquAzh672WEPpfBrFWcikNj5FTfBv9PZnSF3iMSIWacvbOCZgMnEDajR3z GfmwbayApVpSZChqvv8adT2Mcenm5s4bNnh8KprmpziVvtXgZCoZUdC2xyMdFZTzTFGkbg mBjyJ2qaFhWJVKQhx2bNwFm/UQd9XCRZyC0f0MYf1GDVqLHlToLAyvTZOcIbJoQ0khNjzq 12PPHQtWB0yY7tRqjqGfnncDkxEoY/DBluzkn7QFAF5KhSMLvzXqW6AbhKtbp/9Gx8bKVm jab0H2JIALcE4ADMf7Rcfzy44VhzYPyZW3SXGn1DPzsvFa97Slm14+/TwooUMw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1698152207; 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=0k8EHTgBuYIMb5TY+j+PPtTNGdHZXI6Ls9DQ9MAsNmk=; b=HxurSiTuKO2wgC3txgFea08jZZeAAJs30rR0Ke9IgRU24WtZGATMAAdfbbvR7s2lDkpLTQ GnYhPtF3hQn+XxCQ== To: Andrzej Hajda , linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org Cc: Andrzej Hajda , Andi Shyti , Nirmoy Das , Janusz Krzysztofik Subject: Re: [PATCH v2] debugobjects: stop accessing objects after releasing spinlock In-Reply-To: <20230925131359.2948827-1-andrzej.hajda@intel.com> References: <20230925131359.2948827-1-andrzej.hajda@intel.com> Date: Tue, 24 Oct 2023 14:56:47 +0200 Message-ID: <874jigch68.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 25 2023 at 15:13, Andrzej Hajda wrote: > @@ -620,9 +620,8 @@ static void debug_objects_fill_pool(void) > static void > __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack) > { > - enum debug_obj_state state; > struct debug_bucket *db; > - struct debug_obj *obj; > + struct debug_obj *obj, o; > unsigned long flags; > > debug_objects_fill_pool(); > @@ -644,23 +643,19 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack > case ODEBUG_STATE_INACTIVE: > obj->state = ODEBUG_STATE_INIT; > break; > - > - case ODEBUG_STATE_ACTIVE: > - state = obj->state; > - raw_spin_unlock_irqrestore(&db->lock, flags); > - debug_print_object(obj, "init"); > - debug_object_fixup(descr->fixup_init, addr, state); > - return; > - > - case ODEBUG_STATE_DESTROYED: > - raw_spin_unlock_irqrestore(&db->lock, flags); > - debug_print_object(obj, "init"); > - return; > default: > - break; > + o = *obj; > + obj = NULL; > } > > raw_spin_unlock_irqrestore(&db->lock, flags); > + > + if (obj) > + return; Hmm. I'd rather write is this way: case ODEBUG_STATE_INIT: case ODEBUG_STATE_INACTIVE: obj->state = ODEBUG_STATE_INIT; raw_spin_unlock_irqrestore(&db->lock, flags); return; default: break; } o = *obj; raw_spin_unlock_irqrestore(&db->lock, flags); debug_print_object(&o, "init"); if (o.state == ODEBUG_STATE_ACTIVE) debug_object_fixup(descr->fixup_init, addr, o.state); This spares the 'obj' pointer modification and the conditional. The extra raw_spin_unlock_irqrestore() is not the end of the world. > void debug_object_activate(void *addr, const struct debug_obj_descr *descr) ... > default: > - ret = 0; > break; > } > - raw_spin_unlock_irqrestore(&db->lock, flags); > - if (print_object) > - debug_print_object(obj, "activate"); > - return ret; > + } else { > + o.object = addr; > + o.state = ODEBUG_STATE_NOTAVAILABLE; > + o.descr = descr; > + obj = NULL; Hrmm. Just keep the struct debug_obj o = { .object = addr, .state = ODEBUG_STATE_NOTAVAILABLE, .descr = descr }; around and get rid of this else clause. > } > > raw_spin_unlock_irqrestore(&db->lock, flags); > > - /* If NULL the allocation has hit OOM */ > - if (!obj) { > - debug_objects_oom(); > + if (obj) > return 0; Plus a similar change as above to get rid of this conditional and just have the failure path here. > @@ -788,30 +777,29 @@ void debug_object_deactivate(void *addr, const struct debug_obj_descr *descr) > case ODEBUG_STATE_INIT: > case ODEBUG_STATE_INACTIVE: > case ODEBUG_STATE_ACTIVE: > - if (!obj->astate) > + if (!obj->astate) { > obj->state = ODEBUG_STATE_INACTIVE; > - else > - print_object = true; > - break; > - > + break; > + } > + fallthrough; > case ODEBUG_STATE_DESTROYED: > - print_object = true; > + o = *obj; > + obj = NULL; > break; > default: > break; > } > + } else { > + o.object = addr; > + o.state = ODEBUG_STATE_NOTAVAILABLE; > + o.descr = descr; > + obj = NULL; > } Same here. struct debug_obj o = { .object = addr, .state = ODEBUG_STATE_NOTAVAILABLE, .descr = descr }; ... if (obj) { switch (obj->state) { case ODEBUG_STATE_DESTROYED: o = *obj; break; case ODEBUG_STATE_INIT: case ODEBUG_STATE_INACTIVE: case ODEBUG_STATE_ACTIVE: if (obj->astate) { o = *obj; break; } obj->state = ODEBUG_STATE_INACTIVE; fallthrough; default: raw_spin_unlock_irqrestore(&db->lock, flags); return; } } raw_spin_unlock_irqrestore(&db->lock, flags); debug_print_object(&o, "deactivate"); Hmm? > @@ -970,28 +962,27 @@ debug_object_active_state(void *addr, const struct debug_obj_descr *descr, > if (obj) { > switch (obj->state) { > case ODEBUG_STATE_ACTIVE: > - if (obj->astate == expect) > + if (obj->astate == expect) { > obj->astate = next; > - else > - print_object = true; > - break; > - > + break; > + } > + fallthrough; > default: > - print_object = true; > + o = *obj; > + obj = NULL; > break; > } > + } else { > + o.object = addr; > + o.state = ODEBUG_STATE_NOTAVAILABLE; > + o.descr = descr; > + obj = NULL; > } Same pattern here. Thanks, tglx