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Wed, 26 Feb 2025 16:24:56 -0800 (PST) Date: Wed, 26 Feb 2025 16:24:53 -0800 From: Dmitry Torokhov To: Vicki Pfau Cc: Jiri Kosina , Benjamin Tissoires , linux-input@vger.kernel.org Subject: Re: [PATCH 1/3] hid-steam: Move hidraw input (un)registering to work Message-ID: References: <20250205035529.1022143-1-vi@endrift.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250205035529.1022143-1-vi@endrift.com> Hi Vicki, On Tue, Feb 04, 2025 at 07:55:27PM -0800, Vicki Pfau wrote: > Due to an interplay between locking in the input and hid transport subsystems, > attempting to register or deregister the relevant input devices during the > hidraw open/close events can lead to a lock ordering issue. Though this > shouldn't cause a deadlock, this commit moves the input device manipulation to > deferred work to sidestep the issue. > > Signed-off-by: Vicki Pfau > --- > drivers/hid/hid-steam.c | 38 +++++++++++++++++++++++++++++++------- > 1 file changed, 31 insertions(+), 7 deletions(-) > > diff --git a/drivers/hid/hid-steam.c b/drivers/hid/hid-steam.c > index af38fc8eb34f..395dbe642f00 100644 > --- a/drivers/hid/hid-steam.c > +++ b/drivers/hid/hid-steam.c > @@ -313,6 +313,7 @@ struct steam_device { > u16 rumble_left; > u16 rumble_right; > unsigned int sensor_timestamp_us; > + struct work_struct unregister_work; > }; > > static int steam_recv_report(struct steam_device *steam, > @@ -1072,6 +1073,31 @@ static void steam_mode_switch_cb(struct work_struct *work) > } > } > > +static void steam_work_unregister_cb(struct work_struct *work) > +{ > + struct steam_device *steam = container_of(work, struct steam_device, > + unregister_work); > + unsigned long flags; > + bool connected; > + bool opened; > + > + spin_lock_irqsave(&steam->lock, flags); > + opened = steam->client_opened; > + connected = steam->connected; > + spin_unlock_irqrestore(&steam->lock, flags); > + > + if (connected) { > + if (opened) { > + steam_sensors_unregister(steam); > + steam_input_unregister(steam); > + } else { > + steam_set_lizard_mode(steam, lizard_mode); > + steam_input_register(steam); > + steam_sensors_register(steam); > + } > + } > +} > + > static bool steam_is_valve_interface(struct hid_device *hdev) > { > struct hid_report_enum *rep_enum; > @@ -1117,8 +1143,7 @@ static int steam_client_ll_open(struct hid_device *hdev) > steam->client_opened++; > spin_unlock_irqrestore(&steam->lock, flags); > > - steam_sensors_unregister(steam); > - steam_input_unregister(steam); > + schedule_work(&steam->unregister_work); > > return 0; > } > @@ -1135,11 +1160,7 @@ static void steam_client_ll_close(struct hid_device *hdev) > connected = steam->connected && !steam->client_opened; > spin_unlock_irqrestore(&steam->lock, flags); > > - if (connected) { > - steam_set_lizard_mode(steam, lizard_mode); > - steam_input_register(steam); > - steam_sensors_register(steam); > - } > + schedule_work(&steam->unregister_work); > } > > static int steam_client_ll_raw_request(struct hid_device *hdev, > @@ -1231,6 +1252,7 @@ static int steam_probe(struct hid_device *hdev, > INIT_LIST_HEAD(&steam->list); > INIT_WORK(&steam->rumble_work, steam_haptic_rumble_cb); > steam->sensor_timestamp_us = 0; > + INIT_WORK(&steam->unregister_work, steam_work_unregister_cb); > > /* > * With the real steam controller interface, do not connect hidraw. > @@ -1291,6 +1313,7 @@ static int steam_probe(struct hid_device *hdev, > cancel_work_sync(&steam->work_connect); > cancel_delayed_work_sync(&steam->mode_switch); > cancel_work_sync(&steam->rumble_work); > + cancel_work_sync(&steam->unregister_work); > > return ret; > } > @@ -1307,6 +1330,7 @@ static void steam_remove(struct hid_device *hdev) > cancel_delayed_work_sync(&steam->mode_switch); > cancel_work_sync(&steam->work_connect); > cancel_work_sync(&steam->rumble_work); > + cancel_work_sync(&steam->unregister_work); So what happens if you actually cancel the work here? Will you be leaking input device? And bigger question - do you actually need to unregister devices? Or it is just a matter of not delivering data through them when device is in the different mode? Thanks. -- Dmitry