CAPI: Rework locking of controller data structures

This patch applies the mutex so far only protecting the controller list
to (almost) all accesses of controller data structures. It also reworks
waiting on state changes in old_capi_manufacturer so that it no longer
poll and holds a module reference to the controller owner while waiting
(the latter was partly done already). Modification and checking of the
blocked state remains racy by design, the caller is responsible for
dealing with this.

Signed-off-by: Jan Kiszka <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/isdn/capi/kcapi.c

···
 LIST_HEAD(capi_drivers);
 DEFINE_MUTEX(capi_drivers_lock);
 
+struct capi_ctr *capi_controller[CAPI_MAXCONTR];
+DEFINE_MUTEX(capi_controller_lock);
+
 static DEFINE_RWLOCK(application_lock);
-static DEFINE_MUTEX(controller_mutex);
 
 struct capi20_appl *capi_applications[CAPI_MAXAPPL];
-struct capi_ctr *capi_controller[CAPI_MAXCONTR];
 
 static int ncontrollers;
 
···
 	struct capi_ctr *ctr;
 	u16 applid;
 
+	mutex_lock(&capi_controller_lock);
+
 	if (showcapimsgs & 1)
 	        printk(KERN_DEBUG "kcapi: notify up contr %d\n", contr);
 
 	ctr = get_capi_ctr_by_nr(contr);
 	if (ctr) {
 		if (ctr->state == CAPI_CTR_RUNNING)
-			return;
+			goto unlock_out;
 
 		ctr->state = CAPI_CTR_RUNNING;
 
···
 				continue;
 			register_appl(ctr, applid, &ap->rparam);
 		}
+
+		wake_up_interruptible_all(&ctr->state_wait_queue);
 	} else
 		printk(KERN_WARNING "%s: invalid contr %d\n", __func__, contr);
+
+unlock_out:
+	mutex_unlock(&capi_controller_lock);
 }
 
-static void ctr_down(struct capi_ctr *ctr)
+static void ctr_down(struct capi_ctr *ctr, int new_state)
 {
 	struct capi20_appl *ap;
 	u16 applid;
 
-	if (ctr->state == CAPI_CTR_DETECTED)
+	if (ctr->state == CAPI_CTR_DETECTED || ctr->state == CAPI_CTR_DETACHED)
 		return;
 
-	ctr->state = CAPI_CTR_DETECTED;
+	ctr->state = new_state;
 
 	memset(ctr->manu, 0, sizeof(ctr->manu));
 	memset(&ctr->version, 0, sizeof(ctr->version));
···
 		if (ap && !ap->release_in_progress)
 			capi_ctr_put(ctr);
 	}
+
+	wake_up_interruptible_all(&ctr->state_wait_queue);
 }
 
 static void notify_down(u32 contr)
 {
 	struct capi_ctr *ctr;
 
+	mutex_lock(&capi_controller_lock);
+
 	if (showcapimsgs & 1)
 		printk(KERN_DEBUG "kcapi: notify down contr %d\n", contr);
 
 	ctr = get_capi_ctr_by_nr(contr);
 	if (ctr)
-		ctr_down(ctr);
+		ctr_down(ctr, CAPI_CTR_DETECTED);
 	else
 		printk(KERN_WARNING "%s: invalid contr %d\n", __func__, contr);
+
+	mutex_unlock(&capi_controller_lock);
 }
 
 static int
···
  * @ctr:	controller descriptor structure.
  *
  * Called by hardware driver to stop data flow.
+ *
+ * Note: The caller is responsible for synchronizing concurrent state changes
+ * as well as invocations of capi_ctr_handle_message.
  */
 
 void capi_ctr_suspend_output(struct capi_ctr *ctr)
···
  * @ctr:	controller descriptor structure.
  *
  * Called by hardware driver to resume data flow.
+ *
+ * Note: The caller is responsible for synchronizing concurrent state changes
+ * as well as invocations of capi_ctr_handle_message.
  */
 
 void capi_ctr_resume_output(struct capi_ctr *ctr)
···
 {
 	int i;
 
-	mutex_lock(&controller_mutex);
+	mutex_lock(&capi_controller_lock);
 
 	for (i = 0; i < CAPI_MAXCONTR; i++) {
 		if (!capi_controller[i])
 			break;
 	}
 	if (i == CAPI_MAXCONTR) {
-		mutex_unlock(&controller_mutex);
+		mutex_unlock(&capi_controller_lock);
 		printk(KERN_ERR "kcapi: out of controller slots\n");
 	   	return -EBUSY;
 	}
 	capi_controller[i] = ctr;
-
-	mutex_unlock(&controller_mutex);
 
 	ctr->nrecvctlpkt = 0;
 	ctr->nrecvdatapkt = 0;
···
 	ctr->state = CAPI_CTR_DETECTED;
 	ctr->blocked = 0;
 	ctr->traceflag = showcapimsgs;
+	init_waitqueue_head(&ctr->state_wait_queue);
 
 	sprintf(ctr->procfn, "capi/controllers/%d", ctr->cnr);
 	ctr->procent = proc_create_data(ctr->procfn, 0, NULL, ctr->proc_fops, ctr);
 
 	ncontrollers++;
+
+	mutex_unlock(&capi_controller_lock);
+
 	printk(KERN_NOTICE "kcapi: controller [%03d]: %s attached\n",
 			ctr->cnr, ctr->name);
 	return 0;
···
 
 int detach_capi_ctr(struct capi_ctr *ctr)
 {
-	ctr_down(ctr);
+	int err = 0;
 
-	ncontrollers--;
+	mutex_lock(&capi_controller_lock);
 
-	if (ctr->procent) {
-		remove_proc_entry(ctr->procfn, NULL);
-		ctr->procent = NULL;
+	ctr_down(ctr, CAPI_CTR_DETACHED);
+
+	if (capi_controller[ctr->cnr - 1] != ctr) {
+		err = -EINVAL;
+		goto unlock_out;
 	}
 	capi_controller[ctr->cnr - 1] = NULL;
+	ncontrollers--;
+
+	if (ctr->procent)
+		remove_proc_entry(ctr->procfn, NULL);
+
 	printk(KERN_NOTICE "kcapi: controller [%03d]: %s unregistered\n",
 	       ctr->cnr, ctr->name);
 
-	return 0;
+unlock_out:
+	mutex_unlock(&capi_controller_lock);
+
+	return err;
 }
 
 EXPORT_SYMBOL(detach_capi_ctr);
···
 
 u16 capi20_isinstalled(void)
 {
+	u16 ret = CAPI_REGNOTINSTALLED;
 	int i;
-	for (i = 0; i < CAPI_MAXCONTR; i++) {
+
+	mutex_lock(&capi_controller_lock);
+
+	for (i = 0; i < CAPI_MAXCONTR; i++)
 		if (capi_controller[i] &&
-		    capi_controller[i]->state == CAPI_CTR_RUNNING)
-			return CAPI_NOERROR;
-	}
-	return CAPI_REGNOTINSTALLED;
+		    capi_controller[i]->state == CAPI_CTR_RUNNING) {
+			ret = CAPI_NOERROR;
+			break;
+		}
+
+	mutex_unlock(&capi_controller_lock);
+
+	return ret;
 }
 
 EXPORT_SYMBOL(capi20_isinstalled);
···
 
 	write_unlock_irqrestore(&application_lock, flags);
 	
-	mutex_lock(&controller_mutex);
+	mutex_lock(&capi_controller_lock);
+
 	for (i = 0; i < CAPI_MAXCONTR; i++) {
 		if (!capi_controller[i] ||
 		    capi_controller[i]->state != CAPI_CTR_RUNNING)
 			continue;
 		register_appl(capi_controller[i], applid, &ap->rparam);
 	}
-	mutex_unlock(&controller_mutex);
+
+	mutex_unlock(&capi_controller_lock);
 
 	if (showcapimsgs & 1) {
 		printk(KERN_DEBUG "kcapi: appl %d up\n", applid);
···
 	capi_applications[ap->applid - 1] = NULL;
 	write_unlock_irqrestore(&application_lock, flags);
 
-	mutex_lock(&controller_mutex);
+	mutex_lock(&capi_controller_lock);
+
 	for (i = 0; i < CAPI_MAXCONTR; i++) {
 		if (!capi_controller[i] ||
 		    capi_controller[i]->state != CAPI_CTR_RUNNING)
 			continue;
 		release_appl(capi_controller[i], ap->applid);
 	}
-	mutex_unlock(&controller_mutex);
+
+	mutex_unlock(&capi_controller_lock);
 
 	flush_scheduled_work();
 	skb_queue_purge(&ap->recv_queue);
···
 	    || !capi_cmd_valid(CAPIMSG_COMMAND(skb->data))
 	    || !capi_subcmd_valid(CAPIMSG_SUBCOMMAND(skb->data)))
 		return CAPI_ILLCMDORSUBCMDORMSGTOSMALL;
+
+	/*
+	 * The controller reference is protected by the existence of the
+	 * application passed to us. We assume that the caller properly
+	 * synchronizes this service with capi20_release.
+	 */
 	ctr = get_capi_ctr_by_nr(CAPIMSG_CONTROLLER(skb->data));
 	if (!ctr || ctr->state != CAPI_CTR_RUNNING) {
 		ctr = get_capi_ctr_by_nr(1); /* XXX why? */
···
 u16 capi20_get_manufacturer(u32 contr, u8 *buf)
 {
 	struct capi_ctr *ctr;
+	u16 ret;
 
 	if (contr == 0) {
 		strlcpy(buf, capi_manufakturer, CAPI_MANUFACTURER_LEN);
 		return CAPI_NOERROR;
 	}
+
+	mutex_lock(&capi_controller_lock);
+
 	ctr = get_capi_ctr_by_nr(contr);
-	if (!ctr || ctr->state != CAPI_CTR_RUNNING)
-		return CAPI_REGNOTINSTALLED;
-	strlcpy(buf, ctr->manu, CAPI_MANUFACTURER_LEN);
-	return CAPI_NOERROR;
+	if (ctr && ctr->state == CAPI_CTR_RUNNING) {
+		strlcpy(buf, ctr->manu, CAPI_MANUFACTURER_LEN);
+		ret = CAPI_NOERROR;
+	} else
+		ret = CAPI_REGNOTINSTALLED;
+
+	mutex_unlock(&capi_controller_lock);
+	return ret;
 }
 
 EXPORT_SYMBOL(capi20_get_manufacturer);
···
 u16 capi20_get_version(u32 contr, struct capi_version *verp)
 {
 	struct capi_ctr *ctr;
+	u16 ret;
 
 	if (contr == 0) {
 		*verp = driver_version;
 		return CAPI_NOERROR;
 	}
-	ctr = get_capi_ctr_by_nr(contr);
-	if (!ctr || ctr->state != CAPI_CTR_RUNNING)
-		return CAPI_REGNOTINSTALLED;
 
-	memcpy(verp, &ctr->version, sizeof(capi_version));
-	return CAPI_NOERROR;
+	mutex_lock(&capi_controller_lock);
+
+	ctr = get_capi_ctr_by_nr(contr);
+	if (ctr && ctr->state == CAPI_CTR_RUNNING) {
+		memcpy(verp, &ctr->version, sizeof(capi_version));
+		ret = CAPI_NOERROR;
+	} else
+		ret = CAPI_REGNOTINSTALLED;
+
+	mutex_unlock(&capi_controller_lock);
+	return ret;
 }
 
 EXPORT_SYMBOL(capi20_get_version);
···
 u16 capi20_get_serial(u32 contr, u8 *serial)
 {
 	struct capi_ctr *ctr;
+	u16 ret;
 
 	if (contr == 0) {
 		strlcpy(serial, driver_serial, CAPI_SERIAL_LEN);
 		return CAPI_NOERROR;
 	}
-	ctr = get_capi_ctr_by_nr(contr);
-	if (!ctr || ctr->state != CAPI_CTR_RUNNING)
-		return CAPI_REGNOTINSTALLED;
 
-	strlcpy(serial, ctr->serial, CAPI_SERIAL_LEN);
-	return CAPI_NOERROR;
+	mutex_lock(&capi_controller_lock);
+
+	ctr = get_capi_ctr_by_nr(contr);
+	if (ctr && ctr->state == CAPI_CTR_RUNNING) {
+		strlcpy(serial, ctr->serial, CAPI_SERIAL_LEN);
+		ret = CAPI_NOERROR;
+	} else
+		ret = CAPI_REGNOTINSTALLED;
+
+	mutex_unlock(&capi_controller_lock);
+	return ret;
 }
 
 EXPORT_SYMBOL(capi20_get_serial);
···
 u16 capi20_get_profile(u32 contr, struct capi_profile *profp)
 {
 	struct capi_ctr *ctr;
+	u16 ret;
 
 	if (contr == 0) {
 		profp->ncontroller = ncontrollers;
 		return CAPI_NOERROR;
 	}
-	ctr = get_capi_ctr_by_nr(contr);
-	if (!ctr || ctr->state != CAPI_CTR_RUNNING)
-		return CAPI_REGNOTINSTALLED;
 
-	memcpy(profp, &ctr->profile, sizeof(struct capi_profile));
-	return CAPI_NOERROR;
+	mutex_lock(&capi_controller_lock);
+
+	ctr = get_capi_ctr_by_nr(contr);
+	if (ctr && ctr->state == CAPI_CTR_RUNNING) {
+		memcpy(profp, &ctr->profile, sizeof(struct capi_profile));
+		ret = CAPI_NOERROR;
+	} else
+		ret = CAPI_REGNOTINSTALLED;
+
+	mutex_unlock(&capi_controller_lock);
+	return ret;
 }
 
 EXPORT_SYMBOL(capi20_get_profile);
+
+/* Must be called with capi_controller_lock held. */
+static int wait_on_ctr_state(struct capi_ctr *ctr, unsigned int state)
+{
+	DEFINE_WAIT(wait);
+	int retval = 0;
+
+	ctr = capi_ctr_get(ctr);
+	if (!ctr)
+		return -ESRCH;
+
+	for (;;) {
+		prepare_to_wait(&ctr->state_wait_queue, &wait,
+				TASK_INTERRUPTIBLE);
+
+		if (ctr->state == state)
+			break;
+		if (ctr->state == CAPI_CTR_DETACHED) {
+			retval = -ESRCH;
+			break;
+		}
+		if (signal_pending(current)) {
+			retval = -EINTR;
+			break;
+		}
+
+		mutex_unlock(&capi_controller_lock);
+		schedule();
+		mutex_lock(&capi_controller_lock);
+	}
+	finish_wait(&ctr->state_wait_queue, &wait);
+
+	capi_ctr_put(ctr);
+
+	return retval;
+}
 
 #ifdef AVMB1_COMPAT
 static int old_capi_manufacturer(unsigned int cmd, void __user *data)
···
 					   sizeof(avmb1_loadandconfigdef)))
 				return -EFAULT;
 		}
+
+		mutex_lock(&capi_controller_lock);
+
 		ctr = get_capi_ctr_by_nr(ldef.contr);
-		if (!ctr)
-			return -EINVAL;
-		ctr = capi_ctr_get(ctr);
-		if (!ctr)
-			return -ESRCH;
+		if (!ctr) {
+			retval = -EINVAL;
+			goto load_unlock_out;
+		}
+
 		if (ctr->load_firmware == NULL) {
 			printk(KERN_DEBUG "kcapi: load: no load function\n");
-			capi_ctr_put(ctr);
-			return -ESRCH;
+			retval = -ESRCH;
+			goto load_unlock_out;
 		}
 
 		if (ldef.t4file.len <= 0) {
 			printk(KERN_DEBUG "kcapi: load: invalid parameter: length of t4file is %d ?\n", ldef.t4file.len);
-			capi_ctr_put(ctr);
-			return -EINVAL;
+			retval = -EINVAL;
+			goto load_unlock_out;
 		}
 		if (ldef.t4file.data == NULL) {
 			printk(KERN_DEBUG "kcapi: load: invalid parameter: dataptr is 0\n");
-			capi_ctr_put(ctr);
-			return -EINVAL;
+			retval = -EINVAL;
+			goto load_unlock_out;
 		}
 
 		ldata.firmware.user = 1;
···
 
 		if (ctr->state != CAPI_CTR_DETECTED) {
 			printk(KERN_INFO "kcapi: load: contr=%d not in detect state\n", ldef.contr);
-			capi_ctr_put(ctr);
-			return -EBUSY;
+			retval = -EBUSY;
+			goto load_unlock_out;
 		}
 		ctr->state = CAPI_CTR_LOADING;
 
 		retval = ctr->load_firmware(ctr, &ldata);
-
 		if (retval) {
 			ctr->state = CAPI_CTR_DETECTED;
-			capi_ctr_put(ctr);
-			return retval;
+			goto load_unlock_out;
 		}
 
-		while (ctr->state != CAPI_CTR_RUNNING) {
+		retval = wait_on_ctr_state(ctr, CAPI_CTR_RUNNING);
 
-			msleep_interruptible(100);	/* 0.1 sec */
-
-			if (signal_pending(current)) {
-				capi_ctr_put(ctr);
-				return -EINTR;
-			}
-		}
-		capi_ctr_put(ctr);
-		return 0;
+load_unlock_out:
+		mutex_unlock(&capi_controller_lock);
+		return retval;
 
 	case AVMB1_RESETCARD:
 		if (copy_from_user(&rdef, data, sizeof(avmb1_resetdef)))
 			return -EFAULT;
+
+		retval = 0;
+
+		mutex_lock(&capi_controller_lock);
+
 		ctr = get_capi_ctr_by_nr(rdef.contr);
-		if (!ctr)
-			return -ESRCH;
+		if (!ctr) {
+			retval = -ESRCH;
+			goto reset_unlock_out;
+		}
 
 		if (ctr->state == CAPI_CTR_DETECTED)
-			return 0;
+			goto reset_unlock_out;
 
 		ctr->reset_ctr(ctr);
 
-		while (ctr->state > CAPI_CTR_DETECTED) {
+		retval = wait_on_ctr_state(ctr, CAPI_CTR_DETECTED);
 
-			msleep_interruptible(100);	/* 0.1 sec */
-
-			if (signal_pending(current))
-				return -EINTR;
-		}
-		return 0;
-
+reset_unlock_out:
+		mutex_unlock(&capi_controller_lock);
+		return retval;
 	}
 	return -EINVAL;
 }
···
 int capi20_manufacturer(unsigned int cmd, void __user *data)
 {
 	struct capi_ctr *ctr;
+	int retval;
 
 	switch (cmd) {
 #ifdef AVMB1_COMPAT
···
 		if (copy_from_user(&fdef, data, sizeof(kcapi_flagdef)))
 			return -EFAULT;
 
-		ctr = get_capi_ctr_by_nr(fdef.contr);
-		if (!ctr)
-			return -ESRCH;
+		mutex_lock(&capi_controller_lock);
 
-		ctr->traceflag = fdef.flag;
-		printk(KERN_INFO "kcapi: contr [%03d] set trace=%d\n",
-		       ctr->cnr, ctr->traceflag);
-		return 0;
+		ctr = get_capi_ctr_by_nr(fdef.contr);
+		if (ctr) {
+			ctr->traceflag = fdef.flag;
+			printk(KERN_INFO "kcapi: contr [%03d] set trace=%d\n",
+			       ctr->cnr, ctr->traceflag);
+			retval = 0;
+		} else
+			retval = -ESRCH;
+
+		mutex_unlock(&capi_controller_lock);
+
+		return retval;
 	}
 	case KCAPI_CMD_ADDCARD:
 	{
···
 		struct capi_driver *driver = NULL;
 		capicardparams cparams;
 		kcapi_carddef cdef;
-		int retval;
 
 		if ((retval = copy_from_user(&cdef, data, sizeof(cdef))))
 			return retval;

drivers/isdn/capi/kcapi.h

···
 #endif
 
 enum {
+	CAPI_CTR_DETACHED = 0,
 	CAPI_CTR_DETECTED = 1,
 	CAPI_CTR_LOADING  = 2,
 	CAPI_CTR_RUNNING  = 3,
···
 extern struct list_head capi_drivers;
 extern struct mutex capi_drivers_lock;
 
-extern struct capi20_appl *capi_applications[CAPI_MAXAPPL];
 extern struct capi_ctr *capi_controller[CAPI_MAXCONTR];
+extern struct mutex capi_controller_lock;
+
+extern struct capi20_appl *capi_applications[CAPI_MAXAPPL];
 
 #ifdef CONFIG_PROC_FS
 

drivers/isdn/capi/kcapi_proc.c

···
 // ---------------------------------------------------------------------------
 
 static void *controller_start(struct seq_file *seq, loff_t *pos)
+	__acquires(capi_controller_lock)
 {
+	mutex_lock(&capi_controller_lock);
+
 	if (*pos < CAPI_MAXCONTR)
 		return &capi_controller[*pos];
 
···
 }
 
 static void controller_stop(struct seq_file *seq, void *v)
+	__releases(capi_controller_lock)
 {
+	mutex_unlock(&capi_controller_lock);
 }
 
 static int controller_show(struct seq_file *seq, void *v)

include/linux/isdn/capilli.h

···
 	unsigned long nsentdatapkt;
 
 	int cnr;				/* controller number */
-	volatile unsigned short state;		/* controller state */
-	volatile int blocked;			/* output blocked */
+	unsigned short state;			/* controller state */
+	int blocked;				/* output blocked */
 	int traceflag;				/* capi trace */
+	wait_queue_head_t state_wait_queue;
 
 	struct proc_dir_entry *procent;
         char procfn[128];