2 files changed, 25 insertions, 5 deletions

diff --git a/drivers/media/dvb/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb/dvb-core/dvb_ca_en50221.c
index 98ee16773ff2..7e3aeaa7370f 100644
--- a/drivers/media/dvb/dvb-core/dvb_ca_en50221.c
+++ b/drivers/media/dvb/dvb-core/dvb_ca_en50221.c
@@ -93,6 +93,9 @@ struct dvb_ca_slot {
         /* current state of the CAM */
         int slot_state;
 
+        /* mutex used for serializing access to one CI slot */
+        struct mutex slot_lock;
+
         /* Number of CAMCHANGES that have occurred since last processing */
         atomic_t camchange_count;
 
@@ -711,14 +714,20 @@ static int dvb_ca_en50221_write_data(struct dvb_ca_private *ca, int slot, u8 * b
         dprintk("%s\n", __func__);
 
 
-        // sanity check
+        /* sanity check */
         if (bytes_write > ca->slot_info[slot].link_buf_size)
                 return -EINVAL;
 
-        /* check if interface is actually waiting for us to read from it, or if a read is in progress */
+        /* it is possible we are dealing with a single buffer implementation,
+           thus if there is data available for read or if there is even a read
+           already in progress, we do nothing but awake the kernel thread to
+           process the data if necessary. */
         if ((status = ca->pub->read_cam_control(ca->pub, slot, CTRLIF_STATUS)) < 0)
                 goto exitnowrite;
         if (status & (STATUSREG_DA | STATUSREG_RE)) {
+                if (status & STATUSREG_DA)
+                        dvb_ca_en50221_thread_wakeup(ca);
+
                 status = -EAGAIN;
                 goto exitnowrite;
         }
@@ -987,6 +996,8 @@ static int dvb_ca_en50221_thread(void *data)
                 /* go through all the slots processing them */
                 for (slot = 0; slot < ca->slot_count; slot++) {
 
+                        mutex_lock(&ca->slot_info[slot].slot_lock);
+
                         // check the cam status + deal with CAMCHANGEs
                         while (dvb_ca_en50221_check_camstatus(ca, slot)) {
                                 /* clear down an old CI slot if necessary */
@@ -1122,7 +1133,7 @@ static int dvb_ca_en50221_thread(void *data)
 
                         case DVB_CA_SLOTSTATE_RUNNING:
                                 if (!ca->open)
-                                        continue;
+                                        break;
 
                                 // poll slots for data
                                 pktcount = 0;
@@ -1146,6 +1157,8 @@ static int dvb_ca_en50221_thread(void *data)
                                 }
                                 break;
                         }
+
+                        mutex_unlock(&ca->slot_info[slot].slot_lock);
                 }
         }
 
@@ -1181,6 +1194,7 @@ static int dvb_ca_en50221_io_do_ioctl(struct inode *inode, struct file *file,
         switch (cmd) {
         case CA_RESET:
                 for (slot = 0; slot < ca->slot_count; slot++) {
+                        mutex_lock(&ca->slot_info[slot].slot_lock);
                         if (ca->slot_info[slot].slot_state != DVB_CA_SLOTSTATE_NONE) {
                                 dvb_ca_en50221_slot_shutdown(ca, slot);
                                 if (ca->flags & DVB_CA_EN50221_FLAG_IRQ_CAMCHANGE)
@@ -1188,6 +1202,7 @@ static int dvb_ca_en50221_io_do_ioctl(struct inode *inode, struct file *file,
                                                                      slot,
                                                                      DVB_CA_EN50221_CAMCHANGE_INSERTED);
                         }
+                        mutex_unlock(&ca->slot_info[slot].slot_lock);
                 }
                 ca->next_read_slot = 0;
                 dvb_ca_en50221_thread_wakeup(ca);
@@ -1308,7 +1323,9 @@ static ssize_t dvb_ca_en50221_io_write(struct file *file,
                                 goto exit;
                         }
 
+                        mutex_lock(&ca->slot_info[slot].slot_lock);
                         status = dvb_ca_en50221_write_data(ca, slot, fragbuf, fraglen + 2);
+                        mutex_unlock(&ca->slot_info[slot].slot_lock);
                         if (status == (fraglen + 2)) {
                                 written = 1;
                                 break;
@@ -1664,6 +1681,7 @@ int dvb_ca_en50221_init(struct dvb_adapter *dvb_adapter,
                 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;
+                mutex_init(&ca->slot_info[i].slot_lock);
         }
 
         if (signal_pending(current)) {
diff --git a/drivers/media/dvb/dvb-core/dvb_ca_en50221.h b/drivers/media/dvb/dvb-core/dvb_ca_en50221.h
index 8467e63ddc0d..7df2e141187a 100644
--- a/drivers/media/dvb/dvb-core/dvb_ca_en50221.h
+++ b/drivers/media/dvb/dvb-core/dvb_ca_en50221.h
@@ -45,8 +45,10 @@ struct dvb_ca_en50221 {
         /* the module owning this structure */
         struct module* owner;
 
-        /* NOTE: the read_*, write_* and poll_slot_status functions must use locks as
-         * they may be called from several threads at once */
+        /* NOTE: the read_*, write_* and poll_slot_status functions will be
+         * called for different slots concurrently and need to use locks where
+         * and if appropriate. There will be no concurrent access to one slot.
+         */
 
         /* functions for accessing attribute memory on the CAM */
         int (*read_attribute_mem)(struct dvb_ca_en50221* ca, int slot, int address);