[PATCH resend 4/4] nfc: Fix hangup of RC-S380* in port100_send_ack()
From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Date: 2017-02-04 01:17:01
Also in:
lkml
If port100_send_ack() was called twice or more, it has race to hangup.
port100_send_ack() port100_send_ack()
init_completion()
[...]
dev->cmd_cancel = true
/* this removes previous from completion */
init_completion()
[...]
dev->cmd_cancel = true
wait_for_completion()
/* never be waked up */
wait_for_completion()
Like above race, this code is not assuming port100_send_ack() is
called twice or more.
To fix, this checks dev->cmd_cancel to know if prior cancel is
in-flight or not. And never be remove prior task from completion by
using reinit_completion(), so this guarantees to be waked up properly
soon or later.
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
drivers/nfc/port100.c | 37 ++++++++++++++++++++++++-------------
1 file changed, 24 insertions(+), 13 deletions(-)
diff -puN drivers/nfc/port100.c~nfc-port100-hang-fix drivers/nfc/port100.c--- linux-ibmpc/drivers/nfc/port100.c~nfc-port100-hang-fix 2017-01-03 12:32:13.261785257 +0900
+++ linux-ibmpc-hirofumi/drivers/nfc/port100.c 2017-01-03 12:33:51.965364300 +0900@@ -726,23 +726,33 @@ static int port100_submit_urb_for_ack(st static int port100_send_ack(struct port100 *dev) { - int rc; + int rc = 0; mutex_lock(&dev->out_urb_lock); - init_completion(&dev->cmd_cancel_done); - - usb_kill_urb(dev->out_urb); + /* + * If prior cancel is in-flight (dev->cmd_cancel == true), we + * can skip to send cancel. Then this will wait the prior + * cancel, or merged into the next cancel rarely if next + * cancel was started before waiting done. In any case, this + * will be waked up soon or later. + */ + if (!dev->cmd_cancel) { + reinit_completion(&dev->cmd_cancel_done); - dev->out_urb->transfer_buffer = ack_frame; - dev->out_urb->transfer_buffer_length = sizeof(ack_frame); - rc = usb_submit_urb(dev->out_urb, GFP_KERNEL); + usb_kill_urb(dev->out_urb); - /* Set the cmd_cancel flag only if the URB has been successfully - * submitted. It will be reset by the out URB completion callback - * port100_send_complete(). - */ - dev->cmd_cancel = !rc; + dev->out_urb->transfer_buffer = ack_frame; + dev->out_urb->transfer_buffer_length = sizeof(ack_frame); + rc = usb_submit_urb(dev->out_urb, GFP_KERNEL); + + /* + * Set the cmd_cancel flag only if the URB has been + * successfully submitted. It will be reset by the out + * URB completion callback port100_send_complete(). + */ + dev->cmd_cancel = !rc; + } mutex_unlock(&dev->out_urb_lock);
@@ -929,8 +939,8 @@ static void port100_send_complete(struct struct port100 *dev = urb->context; if (dev->cmd_cancel) { + complete_all(&dev->cmd_cancel_done); dev->cmd_cancel = false; - complete(&dev->cmd_cancel_done); } switch (urb->status) {
@@ -1546,6 +1556,7 @@ static int port100_probe(struct usb_inte PORT100_COMM_RF_HEAD_MAX_LEN; dev->skb_tailroom = PORT100_FRAME_TAIL_LEN; + init_completion(&dev->cmd_cancel_done); INIT_WORK(&dev->cmd_complete_work, port100_wq_cmd_complete); /* The first thing to do with the Port-100 is to set the command type
_ -- OGAWA Hirofumi [off-list ref]