Messages in this thread Patch in this message | | | Date | Wed, 9 Feb 2022 16:30:31 +0200 | From | Heikki Krogerus <> | Subject | Re: [BUG] usb: typec: ucsi: possible deadlock in ucsi_pr_swap() and ucsi_handle_connector_change() |
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On Wed, Feb 09, 2022 at 11:50:57AM +0800, Jia-Ju Bai wrote: > Hello, > > My static analysis tool reports a possible deadlock in the ucsi driver in > Linux 5.16: > > ucsi_pr_swap() > mutex_lock(&con->lock); --> Line 962 (Lock A) > wait_for_completion_timeout(&con->complete, ...) --> Line 981 (Wait X) > > ucsi_handle_connector_change() > mutex_lock(&con->lock); --> Line 763 (Lock A) > complete(&con->complete); --> Line 782 (Wake X) > complete(&con->complete); --> Line 807 (Wake X) > > When ucsi_pr_swap() is executed, "Wait X" is performed by holding "Lock A". > If ucsi_handle_connector_change() is executed at this time, "Wake X" cannot > be performed to wake up "Wait X" in ucsi_handle_connector_change(), because > "Lock A" has been already held by ucsi_handle_connector_change(), causing a > possible deadlock. > I find that "Wait X" is performed with a timeout, to relieve the possible > deadlock; but I think this timeout can cause inefficient execution. > > I am not quite sure whether this possible problem is real. > Any feedback would be appreciated, thanks :)
This is probable a regression from commit ad74b8649bea ("usb: typec: ucsi: Preliminary support for alternate modes"). Can you test does this patch fix the issue (attached)?
thanks,
-- heikki From 2ad06425a3df7be656f8a5b3c202aab45554fd17 Mon Sep 17 00:00:00 2001 From: Heikki Krogerus <heikki.krogerus@linux.intel.com> Date: Wed, 9 Feb 2022 17:27:19 +0300 Subject: [PATCH] usb: typec: ucsi: Test fix
Interim.
Not-Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> --- drivers/usb/typec/ucsi/ucsi.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c index f0c2fa19f3e0f..225104beda8be 100644 --- a/drivers/usb/typec/ucsi/ucsi.c +++ b/drivers/usb/typec/ucsi/ucsi.c @@ -956,14 +956,18 @@ static int ucsi_dr_swap(struct typec_port *port, enum typec_data_role role) if (ret < 0) goto out_unlock; + mutex_unlock(&con->lock); + if (!wait_for_completion_timeout(&con->complete, msecs_to_jiffies(UCSI_SWAP_TIMEOUT_MS))) - ret = -ETIMEDOUT; + return -ETIMEDOUT; + + return 0; out_unlock: mutex_unlock(&con->lock); - return ret < 0 ? ret : 0; + return ret; } static int ucsi_pr_swap(struct typec_port *port, enum typec_role role) @@ -992,11 +996,13 @@ static int ucsi_pr_swap(struct typec_port *port, enum typec_role role) if (ret < 0) goto out_unlock; + mutex_unlock(&con->lock); + if (!wait_for_completion_timeout(&con->complete, - msecs_to_jiffies(UCSI_SWAP_TIMEOUT_MS))) { - ret = -ETIMEDOUT; - goto out_unlock; - } + msecs_to_jiffies(UCSI_SWAP_TIMEOUT_MS))) + return -ETIMEDOUT; + + mutex_lock(&con->lock); /* Something has gone wrong while swapping the role */ if (UCSI_CONSTAT_PWR_OPMODE(con->status.flags) != @@ -1372,6 +1378,7 @@ void ucsi_unregister(struct ucsi *ucsi) ucsi->ops->async_write(ucsi, UCSI_CONTROL, &cmd, sizeof(cmd)); for (i = 0; i < ucsi->cap.num_connectors; i++) { + complete(&ucsi->connector[i].complete); cancel_work_sync(&ucsi->connector[i].work); ucsi_unregister_partner(&ucsi->connector[i]); ucsi_unregister_altmodes(&ucsi->connector[i], -- 2.34.1
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