staging: brcm80211: fix thread blocking issue in brcmf_sdbrcm_bus_stop()

The function brcmf_sdbrcm_bus_stop() terminates the watchdog and dpc
thread, but this function can be called from the dpc thread itself.
Stopping the dpc thread is only done when it is not the 'current'
thread.

Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/brcm80211/brcmfmac/dhd_sdio.c

@@ -2694,7 +2694,10 @@ static int brcmf_sdbrcm_dpc_thread(void *data)
 				if (brcmf_sdbrcm_dpc(bus))
 					complete(&bus->dpc_wait);
 			} else {
+				/* after stopping the bus, exit thread */
 				brcmf_sdbrcm_bus_stop(bus);
+				bus->dpc_tsk = NULL;
+				break;
 			}
 		} else
 			break;
@@ -3601,25 +3604,25 @@ void brcmf_sdbrcm_bus_stop(struct brcmf_bus *bus)
 
 	brcmf_dbg(TRACE, "Enter\n");
 
-	down(&bus->sdsem);
-
-	bus_wake(bus);
-
-	/* Enable clock for device interrupts */
-	brcmf_sdbrcm_clkctl(bus, CLK_AVAIL, false);
-
 	if (bus->watchdog_tsk) {
 		send_sig(SIGTERM, bus->watchdog_tsk, 1);
 		kthread_stop(bus->watchdog_tsk);
 		bus->watchdog_tsk = NULL;
 	}
 
-	if (bus->dpc_tsk) {
+	if (bus->dpc_tsk && bus->dpc_tsk != current) {
 		send_sig(SIGTERM, bus->dpc_tsk, 1);
 		kthread_stop(bus->dpc_tsk);
 		bus->dpc_tsk = NULL;
 	}
 
+	down(&bus->sdsem);
+
+	bus_wake(bus);
+
+	/* Enable clock for device interrupts */
+	brcmf_sdbrcm_clkctl(bus, CLK_AVAIL, false);
+
 	/* Disable and clear interrupts at the chip level also */
 	w_sdreg32(bus, 0, offsetof(struct sdpcmd_regs, hostintmask), &retries);
 	local_hostintmask = bus->hostintmask;