memstick: Skip allocating card when removing host

After commit 6827ca573c ("memstick: rtsx_usb_ms: Support runtime power
management"), removing module rtsx_usb_ms will be stuck.

The deadlock is caused by powering on and powering off at the same time,
the former one is when memstick_check() is flushed, and the later is called
by memstick_remove_host().

Soe let's skip allocating card to prevent this issue.

Fixes: 6827ca573c ("memstick: rtsx_usb_ms: Support runtime power management")
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20200925084952.13220-1-kai.heng.feng@canonical.com
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/memstick/core/memstick.c

@@ -441,6 +441,9 @@ static void memstick_check(struct work_struct *work)
 	} else if (host->card->stop)
 		host->card->stop(host->card);
 
+	if (host->removing)
+		goto out_power_off;
+
 	card = memstick_alloc_card(host);
 
 	if (!card) {
@@ -545,6 +548,7 @@ EXPORT_SYMBOL(memstick_add_host);
  */
 void memstick_remove_host(struct memstick_host *host)
 {
+	host->removing = 1;
 	flush_workqueue(workqueue);
 	mutex_lock(&host->lock);
 	if (host->card)

include/linux/memstick.h

@@ -281,6 +281,7 @@ struct memstick_host {
 
 	struct memstick_dev *card;
 	unsigned int        retries;
+	bool removing;
 
 	/* Notify the host that some requests are pending. */
 	void                (*request)(struct memstick_host *host);