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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B5B5FC83F33 for ; Tue, 5 Sep 2023 09:22:11 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 83DAA10E478; Tue, 5 Sep 2023 09:22:11 +0000 (UTC) Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0836E10E478; Tue, 5 Sep 2023 09:22:10 +0000 (UTC) Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by madras.collabora.co.uk (Postfix) with ESMTPSA id 87B076607033; Tue, 5 Sep 2023 10:22:08 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1693905728; bh=IGfQqAyyNenzB8oZ59RATywiYb8GS7xeb/1iuKyZUUg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=cJjn9SS69x/mTUU42RtBztoxjK15CrN3P3hBkbIWwXHcHiah9djECa7RTGsQwLEfJ NDYBvMUUtrKxlmwDj1kp2LC6nwDdEVg0FHPXumAH0oS0j1rtkJgvQWovrrylRWf/p0 bUBGrw0VaApQSzgdssbB9BS6x2WBDKxXCW9EKirpONRDJ/KKBcynsGQiD6A4KU6ueb TNT1tEyMMyMUTp4U3mTMwXwPNyo/B2pl3J6pOrovUecjazEhH2O/z+RsMyqdr82Dgl 0iX/pCiEw8sLofXPFH5hp7wdq7lvQGGIewp4BepTIu9jTekvwc1GaPjo5sfpofUGl5 7WxvM/YPBsoQA== Date: Tue, 5 Sep 2023 11:22:05 +0200 From: Boris Brezillon To: Thomas =?UTF-8?B?SGVsbHN0csO2bQ==?= Message-ID: <20230905112205.35a60cf0@collabora.com> In-Reply-To: <20230905085832.2103-4-thomas.hellstrom@linux.intel.com> References: <20230905085832.2103-1-thomas.hellstrom@linux.intel.com> <20230905085832.2103-4-thomas.hellstrom@linux.intel.com> Organization: Collabora X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Intel-xe] [PATCH 3/3] drm/drm_exec: Work around a WW mutex lockdep oddity X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Danilo Krummrich , intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Christian =?UTF-8?B?S8O2bmln?= Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Tue, 5 Sep 2023 10:58:32 +0200 Thomas Hellstr=C3=B6m wrote: > If *any* object of a certain WW mutex class is locked, lockdep will > consider *all* mutexes of that class as locked. Also the lock allocation > tracking code will apparently register only the address of the first > mutex locked in a sequence. > This has the odd consequence that if that first mutex is unlocked and > its memory then freed, the lock alloc tracking code will assume that memo= ry > is freed with a held lock in there. >=20 > For now, work around that for drm_exec by releasing the first grabbed > object lock last. It's probably a good thing to unlock in reverse order anyway, just like we do for regular locks. >=20 > Related lock alloc tracking warning: > [ 322.660067] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D > [ 322.660070] WARNING: held lock freed! > [ 322.660074] 6.5.0-rc7+ #155 Tainted: G U N > [ 322.660078] ------------------------- > [ 322.660081] kunit_try_catch/4981 is freeing memory ffff888112adc000-ff= ff888112adc3ff, with a lock still held there! > [ 322.660089] ffff888112adc1a0 (reservation_ww_class_mutex){+.+.}-{3:3},= at: drm_exec_lock_obj+0x11a/0x600 [drm_exec] > [ 322.660104] 2 locks held by kunit_try_catch/4981: > [ 322.660108] #0: ffffc9000343fe18 (reservation_ww_class_acquire){+.+.}= -{0:0}, at: test_early_put+0x22f/0x490 [drm_exec_test] > [ 322.660123] #1: ffff888112adc1a0 (reservation_ww_class_mutex){+.+.}-{= 3:3}, at: drm_exec_lock_obj+0x11a/0x600 [drm_exec] > [ 322.660135] > stack backtrace: > [ 322.660139] CPU: 7 PID: 4981 Comm: kunit_try_catch Tainted: G U = N 6.5.0-rc7+ #155 > [ 322.660146] Hardware name: ASUS System Product Name/PRIME B560M-A AC, = BIOS 0403 01/26/2021 > [ 322.660152] Call Trace: > [ 322.660155] > [ 322.660158] dump_stack_lvl+0x57/0x90 > [ 322.660164] debug_check_no_locks_freed+0x20b/0x2b0 > [ 322.660172] slab_free_freelist_hook+0xa1/0x160 > [ 322.660179] ? drm_exec_unlock_all+0x168/0x2a0 [drm_exec] > [ 322.660186] __kmem_cache_free+0xb2/0x290 > [ 322.660192] drm_exec_unlock_all+0x168/0x2a0 [drm_exec] > [ 322.660200] drm_exec_fini+0xf/0x1c0 [drm_exec] > [ 322.660206] test_early_put+0x289/0x490 [drm_exec_test] > [ 322.660215] ? __pfx_test_early_put+0x10/0x10 [drm_exec_test] > [ 322.660222] ? __kasan_check_byte+0xf/0x40 > [ 322.660227] ? __ksize+0x63/0x140 > [ 322.660233] ? drmm_add_final_kfree+0x3e/0xa0 [drm] > [ 322.660289] ? _raw_spin_unlock_irqrestore+0x30/0x60 > [ 322.660294] ? lockdep_hardirqs_on+0x7d/0x100 > [ 322.660301] ? __pfx_kunit_try_run_case+0x10/0x10 [kunit] > [ 322.660310] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [kun= it] > [ 322.660319] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] > [ 322.660328] kthread+0x2e7/0x3c0 > [ 322.660334] ? __pfx_kthread+0x10/0x10 > [ 322.660339] ret_from_fork+0x2d/0x70 > [ 322.660345] ? __pfx_kthread+0x10/0x10 > [ 322.660349] ret_from_fork_asm+0x1b/0x30 > [ 322.660358] > [ 322.660818] ok 8 test_early_put >=20 > Cc: Christian K=C3=B6nig > Cc: Boris Brezillon > Cc: Danilo Krummrich > Cc: dri-devel@lists.freedesktop.org > Signed-off-by: Thomas Hellstr=C3=B6m Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/drm_exec.c | 2 +- > include/drm/drm_exec.h | 35 +++++++++++++++++++++++++++++++---- > 2 files changed, 32 insertions(+), 5 deletions(-) >=20 > diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c > index ff69cf0fb42a..5d2809de4517 100644 > --- a/drivers/gpu/drm/drm_exec.c > +++ b/drivers/gpu/drm/drm_exec.c > @@ -56,7 +56,7 @@ static void drm_exec_unlock_all(struct drm_exec *exec) > struct drm_gem_object *obj; > unsigned long index; > =20 > - drm_exec_for_each_locked_object(exec, index, obj) { > + drm_exec_for_each_locked_object_reverse(exec, index, obj) { > dma_resv_unlock(obj->resv); > drm_gem_object_put(obj); > } > diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h > index e0462361adf9..55764cf7c374 100644 > --- a/include/drm/drm_exec.h > +++ b/include/drm/drm_exec.h > @@ -51,6 +51,20 @@ struct drm_exec { > struct drm_gem_object *prelocked; > }; > =20 > +/** > + * drm_exec_obj() - Return the object for a give drm_exec index > + * @exec: Pointer to the drm_exec context > + * @index: The index. > + * > + * Return: Pointer to the locked object corresponding to @index if > + * index is within the number of locked objects. NULL otherwise. > + */ > +static inline struct drm_gem_object * > +drm_exec_obj(struct drm_exec *exec, unsigned long index) > +{ > + return index < exec->num_objects ? exec->objects[index] : NULL; > +} > + > /** > * drm_exec_for_each_locked_object - iterate over all the locked objects > * @exec: drm_exec object > @@ -59,10 +73,23 @@ struct drm_exec { > * > * Iterate over all the locked GEM objects inside the drm_exec object. > */ > -#define drm_exec_for_each_locked_object(exec, index, obj) \ > - for (index =3D 0, obj =3D (exec)->objects[0]; \ > - index < (exec)->num_objects; \ > - ++index, obj =3D (exec)->objects[index]) > +#define drm_exec_for_each_locked_object(exec, index, obj) \ > + for ((index) =3D 0; ((obj) =3D drm_exec_obj(exec, index)); ++(index)) > + > +/** > + * drm_exec_for_each_locked_object_reverse - iterate over all the locked > + * objects in reverse locking order > + * @exec: drm_exec object > + * @index: unsigned long index for the iteration > + * @obj: the current GEM object > + * > + * Iterate over all the locked GEM objects inside the drm_exec object in > + * reverse locking order. Note that @index may go below zero and wrap, > + * but that will be caught by drm_exec_object(), returning a NULL object. > + */ > +#define drm_exec_for_each_locked_object_reverse(exec, index, obj) \ > + for ((index) =3D (exec)->num_objects - 1; \ > + ((obj) =3D drm_exec_obj(exec, index)); --(index)) > =20 > /** > * drm_exec_until_all_locked - loop until all GEM objects are locked