From patchwork Mon Aug 29 09:18:40 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Whitchurch X-Patchwork-Id: 12957583 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 1189EECAAD5 for ; Mon, 29 Aug 2022 09:18:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229713AbiH2JSs (ORCPT ); Mon, 29 Aug 2022 05:18:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229518AbiH2JSr (ORCPT ); Mon, 29 Aug 2022 05:18:47 -0400 Received: from smtp1.axis.com (smtp1.axis.com [195.60.68.17]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A8FD5AA13; Mon, 29 Aug 2022 02:18:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=axis.com; q=dns/txt; s=axis-central1; t=1661764726; x=1693300726; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=HrikD+LuR2sVPUHOU5CUMyrG4nJVEC9Rl5WE5VrgimU=; b=kPFnjXHdA5RpRZpFuC98vG+v9UqdVIVudmi92ozMpQhpBAfTYdVpyL6Y 7VP8BvNQAVlUlxdRWM85DpcG8RJIrhtEb0YNUmKHSpC+28CpaneRueVLM HRmNDzs2I/LtPxJ2PAY823xjcuJg4zfzZYy3kiNz4MEPs/EjHyZKtdckV wlvTmCOABmDUqIGdTEUIc1HLj+38CtjV3pEfJoTcktMXeRHrt8v+4MfKR 74yDFs87CSRX9kCmuTZYnhPeqPHePJzyUGh/eTEbBr1XQflL1gKB7N2rx RYGZ3Ykngf8j7ppYdVKmwb673RZjYV36ov7e3zGPqTHjmTLB8k5CXegef A==; From: Vincent Whitchurch To: Jonathan Cameron CC: , , Vincent Whitchurch , Lars-Peter Clausen , Matt Ranostay , , Subject: [PATCH v2] iio: Use per-device lockdep class for mlock Date: Mon, 29 Aug 2022 11:18:40 +0200 Message-ID: <20220829091840.2791846-1-vincent.whitchurch@axis.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org If an IIO driver uses callbacks from another IIO driver and calls iio_channel_start_all_cb() from one of its buffer setup ops, then lockdep complains due to the lock nesting, as in the below example with lmp91000. Since the locks are being taken on different IIO devices, there is no actual deadlock. Fix the warning by telling lockdep to use a different class for each iio_device. ============================================ WARNING: possible recursive locking detected -------------------------------------------- python3/23 is trying to acquire lock: (&indio_dev->mlock){+.+.}-{3:3}, at: iio_update_buffers but task is already holding lock: (&indio_dev->mlock){+.+.}-{3:3}, at: enable_store other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&indio_dev->mlock); lock(&indio_dev->mlock); *** DEADLOCK *** May be due to missing lock nesting notation 5 locks held by python3/23: #0: (sb_writers#5){.+.+}-{0:0}, at: ksys_write #1: (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter #2: (kn->active#14){.+.+}-{0:0}, at: kernfs_fop_write_iter #3: (&indio_dev->mlock){+.+.}-{3:3}, at: enable_store #4: (&iio_dev_opaque->info_exist_lock){+.+.}-{3:3}, at: iio_update_buffers Call Trace: __mutex_lock iio_update_buffers iio_channel_start_all_cb lmp91000_buffer_postenable __iio_update_buffers enable_store Fixes: 67e17300dc1d76 ("iio: potentiostat: add LMP91000 support") Signed-off-by: Vincent Whitchurch Reviewed-by: Andy Shevchenko --- Notes: v2: - Use a different lockdep class for each iio_device, instead of using mutex_lock_nested. - Add fixes tag pointing to first IIO driver which used this API. - Trim call stack in commit message. drivers/iio/industrialio-core.c | 5 +++++ include/linux/iio/iio-opaque.h | 2 ++ 2 files changed, 7 insertions(+) diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index 0f4dbda3b9d3..921d8e8643a2 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c @@ -1621,6 +1621,8 @@ static void iio_dev_release(struct device *device) iio_device_detach_buffers(indio_dev); + lockdep_unregister_key(&iio_dev_opaque->mlock_key); + ida_free(&iio_ida, iio_dev_opaque->id); kfree(iio_dev_opaque); } @@ -1680,6 +1682,9 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv) INIT_LIST_HEAD(&iio_dev_opaque->buffer_list); INIT_LIST_HEAD(&iio_dev_opaque->ioctl_handlers); + lockdep_register_key(&iio_dev_opaque->mlock_key); + lockdep_set_class(&indio_dev->mlock, &iio_dev_opaque->mlock_key); + return indio_dev; } EXPORT_SYMBOL(iio_device_alloc); diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-opaque.h index 6b3586b3f952..d1f8b30a7c8b 100644 --- a/include/linux/iio/iio-opaque.h +++ b/include/linux/iio/iio-opaque.h @@ -11,6 +11,7 @@ * checked by device drivers but should be considered * read-only as this is a core internal bit * @driver_module: used to make it harder to undercut users + * @mlock_key: lockdep class for iio_dev lock * @info_exist_lock: lock to prevent use during removal * @trig_readonly: mark the current trigger immutable * @event_interface: event chrdevs associated with interrupt lines @@ -42,6 +43,7 @@ struct iio_dev_opaque { int currentmode; int id; struct module *driver_module; + struct lock_class_key mlock_key; struct mutex info_exist_lock; bool trig_readonly; struct iio_event_interface *event_interface;