[PATCH] DVB: Fix locking problems and code cleanup

Fix locking problems and code cleanup

Signed-off-by: Andrew de Quincey <[e-mail]>
Signed-off-by: Johannes Stezenbach <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/media/dvb/dvb-core/dvb_ca_en50221.c

···
 #include <linux/moduleparam.h>
 #include <linux/vmalloc.h>
 #include <linux/delay.h>
-#include <linux/rwsem.h>
+#include <linux/spinlock.h>
 #include <linux/sched.h>
 
 #include "dvb_ca_en50221.h"
···
 
 	/* size of the buffer to use when talking to the CAM */
 	int link_buf_size;
-
-	/* semaphore for syncing access to slot structure */
-	struct rw_semaphore sem;
 
 	/* buffer for incoming packets */
 	struct dvb_ringbuffer rx_buffer;
···
 	if (ebuf == NULL) {
 		int buf_free;
 
-		down_read(&ca->slot_info[slot].sem);
 		if (ca->slot_info[slot].rx_buffer.data == NULL) {
-			up_read(&ca->slot_info[slot].sem);
 			status = -EIO;
 			goto exit;
 		}
 		buf_free = dvb_ringbuffer_free(&ca->slot_info[slot].rx_buffer);
-		up_read(&ca->slot_info[slot].sem);
 
 		if (buf_free < (ca->slot_info[slot].link_buf_size + DVB_RINGBUFFER_PKTHDRSIZE)) {
 			status = -EAGAIN;
···
 
 	/* OK, add it to the receive buffer, or copy into external buffer if supplied */
 	if (ebuf == NULL) {
-		down_read(&ca->slot_info[slot].sem);
 		if (ca->slot_info[slot].rx_buffer.data == NULL) {
-			up_read(&ca->slot_info[slot].sem);
 			status = -EIO;
 			goto exit;
 		}
 		dvb_ringbuffer_pkt_write(&ca->slot_info[slot].rx_buffer, buf, bytes_read);
-		up_read(&ca->slot_info[slot].sem);
 	} else {
 		memcpy(ebuf, buf, bytes_read);
 	}
···
 {
 	dprintk("%s\n", __FUNCTION__);
 
-	down_write(&ca->slot_info[slot].sem);
 	ca->pub->slot_shutdown(ca->pub, slot);
 	ca->slot_info[slot].slot_state = DVB_CA_SLOTSTATE_NONE;
-	vfree(ca->slot_info[slot].rx_buffer.data);
-	ca->slot_info[slot].rx_buffer.data = NULL;
-	up_write(&ca->slot_info[slot].sem);
 
 	/* need to wake up all processes to check if they're now
 	   trying to write to a defunct CAM */
···
 
 	case DVB_CA_SLOTSTATE_RUNNING:
 		if (ca->open)
-			dvb_ca_en50221_read_data(ca, slot, NULL, 0);
+			dvb_ca_en50221_thread_wakeup(ca);
 		break;
 	}
 }
···
 					break;
 				}
 
-				rxbuf = vmalloc(RX_BUFFER_SIZE);
-				if (rxbuf == NULL) {
-					printk("dvb_ca adapter %d: Unable to allocate CAM rx buffer :(\n", ca->dvbdev->adapter->num);
-					ca->slot_info[slot].slot_state = DVB_CA_SLOTSTATE_INVALID;
-					dvb_ca_en50221_thread_update_delay(ca);
-					break;
+				if (ca->slot_info[slot].rx_buffer.data == NULL) {
+					rxbuf = vmalloc(RX_BUFFER_SIZE);
+					if (rxbuf == NULL) {
+						printk("dvb_ca adapter %d: Unable to allocate CAM rx buffer :(\n", ca->dvbdev->adapter->num);
+						ca->slot_info[slot].slot_state = DVB_CA_SLOTSTATE_INVALID;
+						dvb_ca_en50221_thread_update_delay(ca);
+						break;
+					}
+					dvb_ringbuffer_init(&ca->slot_info[slot].rx_buffer, rxbuf, RX_BUFFER_SIZE);
 				}
-				down_write(&ca->slot_info[slot].sem);
-				dvb_ringbuffer_init(&ca->slot_info[slot].rx_buffer, rxbuf, RX_BUFFER_SIZE);
-				up_write(&ca->slot_info[slot].sem);
 
 				ca->pub->slot_ts_enable(ca->pub, slot);
 				ca->slot_info[slot].slot_state = DVB_CA_SLOTSTATE_RUNNING;
···
 				if (!ca->open)
 					continue;
 
-				// no need to poll if the CAM supports IRQs
-				if (ca->slot_info[slot].da_irq_supported)
-					break;
-
-				// poll mode
+				// poll slots for data
 				pktcount = 0;
 				while ((status = dvb_ca_en50221_read_data(ca, slot, NULL, 0)) > 0) {
 					if (!ca->open)
···
 /**
  * Condition for waking up in dvb_ca_en50221_io_read_condition
  */
-static int dvb_ca_en50221_io_read_condition(struct dvb_ca_private *ca, int *result, int *_slot)
+static int dvb_ca_en50221_io_read_condition(struct dvb_ca_private *ca,
+					    int *result, int *_slot)
 {
 	int slot;
 	int slot_count = 0;
 	int idx;
-	int fraglen;
+	size_t fraglen;
 	int connection_id = -1;
 	int found = 0;
 	u8 hdr[2];
···
 		if (ca->slot_info[slot].slot_state != DVB_CA_SLOTSTATE_RUNNING)
 			goto nextslot;
 
-		down_read(&ca->slot_info[slot].sem);
-
 		if (ca->slot_info[slot].rx_buffer.data == NULL) {
-			up_read(&ca->slot_info[slot].sem);
 			return 0;
 		}
 
···
 			idx = dvb_ringbuffer_pkt_next(&ca->slot_info[slot].rx_buffer, idx, &fraglen);
 		}
 
-		if (!found)
-			up_read(&ca->slot_info[slot].sem);
-
-	      nextslot:
+nextslot:
 		slot = (slot + 1) % ca->slot_count;
 		slot_count++;
 	}
···
 		goto exit;
 	status = pktlen;
 
-      exit:
-	up_read(&ca->slot_info[slot].sem);
+exit:
 	return status;
 }
 
···
 	for (i = 0; i < ca->slot_count; i++) {
 
 		if (ca->slot_info[i].slot_state == DVB_CA_SLOTSTATE_RUNNING) {
-			down_write(&ca->slot_info[i].sem);
 			if (ca->slot_info[i].rx_buffer.data != NULL) {
+				/* it is safe to call this here without locks because
+				 * ca->open == 0. Data is not read in this case */
 				dvb_ringbuffer_flush(&ca->slot_info[i].rx_buffer);
 			}
-			up_write(&ca->slot_info[i].sem);
 		}
 	}
 
···
 	dprintk("%s\n", __FUNCTION__);
 
 	if (dvb_ca_en50221_io_read_condition(ca, &result, &slot) == 1) {
-		up_read(&ca->slot_info[slot].sem);
 		mask |= POLLIN;
 	}
 
···
 	poll_wait(file, &ca->wait_queue, wait);
 
 	if (dvb_ca_en50221_io_read_condition(ca, &result, &slot) == 1) {
-		up_read(&ca->slot_info[slot].sem);
 		mask |= POLLIN;
 	}
 
···
 		ca->slot_info[i].slot_state = DVB_CA_SLOTSTATE_NONE;
 		atomic_set(&ca->slot_info[i].camchange_count, 0);
 		ca->slot_info[i].camchange_type = DVB_CA_EN50221_CAMCHANGE_REMOVED;
-		init_rwsem(&ca->slot_info[i].sem);
 	}
 
 	if (signal_pending(current)) {
···
 	ca->thread_pid = ret;
 	return 0;
 
-      error:
+error:
 	if (ca != NULL) {
 		if (ca->dvbdev != NULL)
 			dvb_unregister_device(ca->dvbdev);
···
 
 	for (i = 0; i < ca->slot_count; i++) {
 		dvb_ca_en50221_slot_shutdown(ca, i);
+		if (ca->slot_info[i].rx_buffer.data != NULL) {
+			vfree(ca->slot_info[i].rx_buffer.data);
+		}
 	}
 	kfree(ca->slot_info);
 	dvb_unregister_device(ca->dvbdev);