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 9FC8A3375DD for ; Mon, 26 Jan 2026 16:53:06 +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=1769446386; cv=none; b=Hpk/+QEHF9Me5zmzPeDb966aSlHPaWQdBYsQY6PY/uc5gOoVeZBHu0cMay7LxPy6pOSJFWuB5/7yncROQellYifmyoWselYulTPJBdxLaOJ5EhinpXhsDPJom2L67ixmBKPwWAt0vhLO9S/ZGQ305lZUngBGBMFFqp0ZPruR40g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769446386; c=relaxed/simple; bh=lytw1C9L2scVcTC6h8ixCo4+Rf/PYZPg7Nk4de1rM9Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sONqEZOL4J9R9xMkCrj6JKZmv+VLKCP0xKuuwWNJb0Y+2herGZmb5DRF/1zmmEieu/EU/ApdkeMA+KmyRHrdzeCCes7/y1BYXGh44mcsOK8QEaNjJknZ4j0fElYIcZvMEZuX+whuGZXr6H76HWyp71hGda7bn0HUdhmbTGmUpn0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ay4r3VqQ; 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="ay4r3VqQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBFDDC16AAE; Mon, 26 Jan 2026 16:53:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769446386; bh=lytw1C9L2scVcTC6h8ixCo4+Rf/PYZPg7Nk4de1rM9Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ay4r3VqQScZoud6RNJ8XDmeOxFvUn/ghoEu6ux1caKr2LRF/CWsOEcybsnVLw0c5e wtcSASGCybHTLF8lzn12+iALl3A7RRMfEJL1cvnGaVNCbSd8k4OG6FDWoBwZenAek0 jskrmIA4MCX8BFub7whqjiorbVcZ0R6YohviS2LTQs4dmKjEJoxwuWJtRYEcjKyo6J qujFG3jx/cM/aFX45HJBf/xLeYshfnr57iyhIXIDNkrXmp9G4vPxEQiZcSZuISr87h 56nUV9cCASBG7gkHxzs4+14kYwEZzTyPhuXurA8OBvmxKilhJQuYauKN2jaHNNKJjx 5HYcJO0OnZLPQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Rasmus Villemoes , Peter Rosin , Jonathan Cameron , Sasha Levin Subject: [PATCH 6.18.y 2/2] iio: core: add separate lockdep class for info_exist_lock Date: Mon, 26 Jan 2026 11:53:03 -0500 Message-ID: <20260126165303.3408060-2-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260126165303.3408060-1-sashal@kernel.org> References: <2026012654-trend-outback-5af6@gregkh> <20260126165303.3408060-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Rasmus Villemoes [ Upstream commit 9910159f06590c17df4fbddedaabb4c0201cc4cb ] When one iio device is a consumer of another, it is possible that the ->info_exist_lock of both ends up being taken when reading the value of the consumer device. Since they currently belong to the same lockdep class (being initialized in a single location with mutex_init()), that results in a lockdep warning CPU0 ---- lock(&iio_dev_opaque->info_exist_lock); lock(&iio_dev_opaque->info_exist_lock); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by sensors/414: #0: c31fd6dc (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0x44/0x4e4 #1: c4f5a1c4 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x1c/0xac #2: c2827548 (kn->active#34){.+.+}-{0:0}, at: kernfs_seq_start+0x30/0xac #3: c1dd2b68 (&iio_dev_opaque->info_exist_lock){+.+.}-{3:3}, at: iio_read_channel_processed_scale+0x24/0xd8 stack backtrace: CPU: 0 UID: 0 PID: 414 Comm: sensors Not tainted 6.17.11 #5 NONE Hardware name: Generic AM33XX (Flattened Device Tree) Call trace: unwind_backtrace from show_stack+0x10/0x14 show_stack from dump_stack_lvl+0x44/0x60 dump_stack_lvl from print_deadlock_bug+0x2b8/0x334 print_deadlock_bug from __lock_acquire+0x13a4/0x2ab0 __lock_acquire from lock_acquire+0xd0/0x2c0 lock_acquire from __mutex_lock+0xa0/0xe8c __mutex_lock from mutex_lock_nested+0x1c/0x24 mutex_lock_nested from iio_read_channel_raw+0x20/0x6c iio_read_channel_raw from rescale_read_raw+0x128/0x1c4 rescale_read_raw from iio_channel_read+0xe4/0xf4 iio_channel_read from iio_read_channel_processed_scale+0x6c/0xd8 iio_read_channel_processed_scale from iio_hwmon_read_val+0x68/0xbc iio_hwmon_read_val from dev_attr_show+0x18/0x48 dev_attr_show from sysfs_kf_seq_show+0x80/0x110 sysfs_kf_seq_show from seq_read_iter+0xdc/0x4e4 seq_read_iter from vfs_read+0x238/0x2e4 vfs_read from ksys_read+0x6c/0xec ksys_read from ret_fast_syscall+0x0/0x1c Just as the mlock_key already has its own lockdep class, add a lock_class_key for the info_exist mutex. Note that this has in theory been a problem since before IIO first left staging, but it only occurs when a chain of consumers is in use and that is not often done. Fixes: ac917a81117c ("staging:iio:core set the iio_dev.info pointer to null on unregister under lock.") Signed-off-by: Rasmus Villemoes Reviewed-by: Peter Rosin Cc: Signed-off-by: Jonathan Cameron Signed-off-by: Sasha Levin --- drivers/iio/industrialio-core.c | 4 +++- include/linux/iio/iio-opaque.h | 2 ++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index f69deefcfb6fd..117ffad4f3769 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -1657,6 +1657,7 @@ static void iio_dev_release(struct device *device) mutex_destroy(&iio_dev_opaque->info_exist_lock); mutex_destroy(&iio_dev_opaque->mlock); + lockdep_unregister_key(&iio_dev_opaque->info_exist_key); lockdep_unregister_key(&iio_dev_opaque->mlock_key); ida_free(&iio_ida, iio_dev_opaque->id); @@ -1717,9 +1718,10 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv) INIT_LIST_HEAD(&iio_dev_opaque->ioctl_handlers); lockdep_register_key(&iio_dev_opaque->mlock_key); + lockdep_register_key(&iio_dev_opaque->info_exist_key); mutex_init_with_key(&iio_dev_opaque->mlock, &iio_dev_opaque->mlock_key); - mutex_init(&iio_dev_opaque->info_exist_lock); + mutex_init_with_key(&iio_dev_opaque->info_exist_lock, &iio_dev_opaque->info_exist_key); indio_dev->dev.parent = parent; indio_dev->dev.type = &iio_device_type; diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-opaque.h index 4247497f3f8bd..b87841a355f80 100644 --- a/include/linux/iio/iio-opaque.h +++ b/include/linux/iio/iio-opaque.h @@ -14,6 +14,7 @@ * @mlock: lock used to prevent simultaneous device state changes * @mlock_key: lockdep class for iio_dev lock * @info_exist_lock: lock to prevent use during removal + * @info_exist_key: lockdep class for info_exist lock * @trig_readonly: mark the current trigger immutable * @event_interface: event chrdevs associated with interrupt lines * @attached_buffers: array of buffers statically attached by the driver @@ -47,6 +48,7 @@ struct iio_dev_opaque { struct mutex mlock; struct lock_class_key mlock_key; struct mutex info_exist_lock; + struct lock_class_key info_exist_key; bool trig_readonly; struct iio_event_interface *event_interface; struct iio_buffer **attached_buffers; -- 2.51.0