From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 3F35D6B0279 for ; Fri, 26 May 2017 12:21:15 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id j28so18324372pfk.14 for ; Fri, 26 May 2017 09:21:15 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id t8si1330155pfa.36.2017.05.26.09.21.13 for ; Fri, 26 May 2017 09:21:14 -0700 (PDT) Date: Fri, 26 May 2017 17:21:08 +0100 From: Catalin Marinas Subject: Re: [PATCH v2 2/3] mm: kmemleak: Factor object reference updating out of scan_block() Message-ID: <20170526162107.GC30853@e104818-lin.cambridge.arm.com> References: <1495726937-23557-1-git-send-email-catalin.marinas@arm.com> <1495726937-23557-3-git-send-email-catalin.marinas@arm.com> <20170526160916.ptlc2huao3bn4qwq@hermes.olymp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170526160916.ptlc2huao3bn4qwq@hermes.olymp> Sender: owner-linux-mm@kvack.org List-ID: To: Luis Henriques Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Andy Lutomirski , "Luis R. Rodriguez" , Andrew Morton On Fri, May 26, 2017 at 05:09:17PM +0100, Luis Henriques wrote: > On Thu, May 25, 2017 at 04:42:16PM +0100, Catalin Marinas wrote: > > The scan_block() function updates the number of references (pointers) to > > objects, adding them to the gray_list when object->min_count is reached. > > The patch factors out this functionality into a separate update_refs() > > function. > > > > Cc: Michal Hocko > > Cc: Andy Lutomirski > > Cc: "Luis R. Rodriguez" > > Signed-off-by: Catalin Marinas > > --- > > mm/kmemleak.c | 43 +++++++++++++++++++++++++------------------ > > 1 file changed, 25 insertions(+), 18 deletions(-) > > > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > > index 964b12eba2c1..266482f460c2 100644 > > --- a/mm/kmemleak.c > > +++ b/mm/kmemleak.c > > @@ -1188,6 +1188,30 @@ static bool update_checksum(struct kmemleak_object *object) > > } > > > > /* > > + * Update an object's references. object->lock must be held by the caller. > > + */ > > +static void update_refs(struct kmemleak_object *object) > > +{ > > + if (!color_white(object)) { > > + /* non-orphan, ignored or new */ > > + return; > > + } > > + > > + /* > > + * Increase the object's reference count (number of pointers to the > > + * memory block). If this count reaches the required minimum, the > > + * object's color will become gray and it will be added to the > > + * gray_list. > > + */ > > + object->count++; > > + if (color_gray(object)) { > > + /* put_object() called when removing from gray_list */ > > + WARN_ON(!get_object(object)); > > + list_add_tail(&object->gray_list, &gray_list); > > + } > > +} > > + > > +/* > > * Memory scanning is a long process and it needs to be interruptable. This > > * function checks whether such interrupt condition occurred. > > */ > > @@ -1259,24 +1283,7 @@ static void scan_block(void *_start, void *_end, > > * enclosed by scan_mutex. > > */ > > spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING); > > - if (!color_white(object)) { > > - /* non-orphan, ignored or new */ > > - spin_unlock(&object->lock); > > - continue; > > - } > > - > > - /* > > - * Increase the object's reference count (number of pointers > > - * to the memory block). If this count reaches the required > > - * minimum, the object's color will become gray and it will be > > - * added to the gray_list. > > - */ > > - object->count++; > > - if (color_gray(object)) { > > - /* put_object() called when removing from gray_list */ > > - WARN_ON(!get_object(object)); > > - list_add_tail(&object->gray_list, &gray_list); > > - } > > + update_refs(object); > > spin_unlock(&object->lock); > > FWIW, I've tested this patchset and I don't see kmemleak triggering the > false positives anymore. Thanks for re-testing (I dropped your tested-by from the initial patch since I made a small modification). > I've also done a quick review and couldn't find anything obviously > incorrect, just a question: why didn't you moved the spin_lock/unlock into > update_refs() too? It would save you 2 lines in the next patch :) There is a small difference: for the first object it needs to check color_gray() and access object->excess_ref while the lock is held. It doesn't need this in the second case. I could've written it in different ways but probably with a similar number of lines; I just found this clearer. -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org