From b7644592bd0d78cf7aba377124c2d3082607685b Mon Sep 17 00:00:00 2001 From: Jason Gerecke Date: Fri, 15 Oct 2021 10:28:02 +0800 Subject: [PATCH] HID: wacom: Shrink critical section in `wacom_add_shared_data` The size of the critical section in this function appears to be larger than necessary. The `wacom_udev_list_lock` exists to ensure that one interface cannot begin checking if a shared object exists while a second interface is doing the same (otherwise both could determine that no object exists yet and create their own independent objects rather than sharing just one). It should be safe for the critical section to end once a fresly-allocated shared object would be found by other threads (i.e., once it has been added to `wacom_udev_list`, which is looped over by `wacom_get_hdev_data`). This commit is a necessary pre-requisite for a later change to swap the use of `devm_add_action` with `devm_add_action_or_reset`, which would otherwise deadlock in its error case. Signed-off-by: Jason Gerecke Signed-off-by: Jiri Kosina --- drivers/hid/wacom_sys.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index 93f49b7..62f50e4 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -881,8 +881,8 @@ static int wacom_add_shared_data(struct hid_device *hdev) if (!data) { data = kzalloc(sizeof(struct wacom_hdev_data), GFP_KERNEL); if (!data) { - retval = -ENOMEM; - goto out; + mutex_unlock(&wacom_udev_list_lock); + return -ENOMEM; } kref_init(&data->kref); @@ -890,11 +890,12 @@ static int wacom_add_shared_data(struct hid_device *hdev) list_add_tail(&data->list, &wacom_udev_list); } + mutex_unlock(&wacom_udev_list_lock); + wacom_wac->shared = &data->shared; retval = devm_add_action(&hdev->dev, wacom_remove_shared_data, wacom); if (retval) { - mutex_unlock(&wacom_udev_list_lock); wacom_remove_shared_data(wacom); return retval; } @@ -904,8 +905,6 @@ static int wacom_add_shared_data(struct hid_device *hdev) else if (wacom_wac->features.device_type & WACOM_DEVICETYPE_PEN) wacom_wac->shared->pen = hdev; -out: - mutex_unlock(&wacom_udev_list_lock); return retval; } -- 2.7.4