From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D97B821FF36; Mon, 7 Jul 2025 11:32:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751887934; cv=none; b=mLqL14YZ1NAr9d5suZ3fvsuVzWi2dGyw8FWFBzSTt3sHIrawUOhFvRMakrAonBNldm+FgtpD/mh2eODJxXdGgNPhjW4PtsQVoD/BZl2wlL/W0eJjuF7whrZDTrvUMr7wK5gCao4rTIXZh3A1Ru1J+dx0IVqsmG6ZgUDHqG7Fz+w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751887934; c=relaxed/simple; bh=KJ9ivJDcFfm+HtMTDVXkf8LFJkwB6s4Vcp0E0EjRA2c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JkG688BjzStHvNHkKqfuwnJeZnDyrPHaZp+9+S7GkDcN1g1nnXnxDyKEJy2tgT7jvQ1f8R+gCki5EtjFqEfPL/113SUVjoLboBZlkSiFcWLbeHyOtmgnDgNAC2FpuyXkZmYlctsAN96Od874Z9mYq+qSagWtFrh4iUUOwht7u2Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ObJ/+U2n; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ObJ/+U2n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 95FD5C4CEE3; Mon, 7 Jul 2025 11:32:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751887933; bh=KJ9ivJDcFfm+HtMTDVXkf8LFJkwB6s4Vcp0E0EjRA2c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ObJ/+U2noTTkjAYPn1YG/pdjcVIrO/IOmmZsAYxhvnAnuEEw46VjHz21QdgfI8cKT +7NSFG8lrtgTjmywMa+vSb4IahbVlsmSRAt7+EOguDQ/KXOcN8yLq86WtCfj/iQqjm iMnILzLyLzqgvWZ5zRVkCEoY3pLWijnv0qT9pHeJUcS4/EAG4LuQpQTCw+mOWrmedl aoeDXJgFYb5adTum4hw3gLcZESV5SUWXdTax8l3IIvEL1mxa5h3565ySjNU1Le1ZWW MVAlLNI7a0P/eIN7r3+qI4dWVJBoCnTb9ClSSRXMoxWDHybNjqnWeOkN0VfAVYkCjz dJOZ4soLHExRg== Date: Mon, 7 Jul 2025 14:32:02 +0300 From: Mike Rapoport To: Peter Zijlstra , "Liam R. Howlett" Cc: Andrew Morton , Andy Lutomirski , Borislav Petkov , Daniel Gomez , Dave Hansen , Ingo Molnar , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , "H. Peter Anvin" , Petr Pavlu , Sami Tolvanen , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH 3/8] execmem: rework execmem_cache_free() Message-ID: References: <20250704134943.3524829-1-rppt@kernel.org> <20250704134943.3524829-4-rppt@kernel.org> <20250707111102.GF1613200@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250707111102.GF1613200@noisy.programming.kicks-ass.net> On Mon, Jul 07, 2025 at 01:11:02PM +0200, Peter Zijlstra wrote: > On Fri, Jul 04, 2025 at 04:49:38PM +0300, Mike Rapoport wrote: > > static bool execmem_cache_free(void *ptr) > > { > > struct maple_tree *busy_areas = &execmem_cache.busy_areas; > > unsigned long addr = (unsigned long)ptr; > > MA_STATE(mas, busy_areas, addr, addr); > > void *area; > > + int err; > > + > > + guard(mutex)(&execmem_cache.mutex); > > > > area = mas_walk(&mas); > > + if (!area) > > return false; > > > > + err = __execmem_cache_free(&mas, ptr, GFP_KERNEL | __GFP_NORETRY); > > + if (err) > > + goto err_slowpath; > > > > schedule_work(&execmem_cache_clean_work); > > > > return true; > > + > > +err_slowpath: > > + mas_store_gfp(&mas, pending_free_set(ptr), GFP_KERNEL); > > + execmem_cache.pending_free_cnt++; > > + schedule_delayed_work(&execmem_cache_free_work, FREE_DELAY); > > + return true; > > } > > This is a bit if an anti-pattern, using guard() and error goto. Since Good to know :) > there is only the one site, its best to write it like so: > > static bool execmem_cache_free(void *ptr) > { > struct maple_tree *busy_areas = &execmem_cache.busy_areas; > unsigned long addr = (unsigned long)ptr; > MA_STATE(mas, busy_areas, addr, addr); > void *area; > int err; > > guard(mutex)(&execmem_cache.mutex); > > area = mas_walk(&mas); > if (!area) > return false; > > err = __execmem_cache_free(&mas, ptr, GFP_KERNEL | __GFP_NORETRY); > if (err) { > mas_store_gfp(&mas, pending_free_set(ptr), GFP_KERNEL); > execmem_cache.pending_free_cnt++; > schedule_delayed_work(&execmem_cache_free_work, FREE_DELAY); > return true; > } > > schedule_work(&execmem_cache_clean_work); > return true; > } > > And now I have to ask what happens if mas_store_gfp() returns an error? AFAIU it won't. mas points to exact slot we've got the area from, nothing else can modify the tree because of the mutex, so that mas_store_gfp() essentially updates the value at an existing entry. I'll add a comment about it. Added @Liam to make sure I'm not saying nonsense :) -- Sincerely yours, Mike.