Re: [RESEND 3/4] vme: change bus error handling scheme

[Martyn Welch <martyn@xxxxxxxxxxxx>]

On 18/09/15 00:01, dmitry.kalinkin@xxxxxxxxx wrote:
> From: Dmitry Kalinkin <dmitry.kalinkin@xxxxxxxxx>
>
> The current VME bus error handler adds errors to the bridge error list.
> vme_master_{read,write} then traverses that list to look for relevant
> errors.
>
> Such scheme didn't work well for accesses going through vme_master_mmap
> because they would also allocate a vme_bus_error, but have no way to do
> vme_clear_errors call to free that memory.
>
> This changes the error handling process to be other way around: now
> vme_master_{read,write} defines a window in VME address space that will
> catch possible errors.  VME bus error interrupt only traverses these
> windows and marks those that had errors in them.
>
> Signed-off-by: Dmitry Kalinkin <dmitry.kalinkin@xxxxxxxxx>
> Cc: Igor Alekseev <igor.alekseev@xxxxxxx>

This one is currently causing the following warnings at build time:

  CC      drivers/vme/bridges/vme_tsi148.o
drivers/vme/bridges/vme_tsi148.c: In function ‘tsi148_master_read’:
drivers/vme/bridges/vme_tsi148.c:1254:14: warning: ‘handler’ may be used 
uninitialized in this function [-Wmaybe-uninitialized]
   if (handler->num_errors) {
              ^
drivers/vme/bridges/vme_tsi148.c: In function ‘tsi148_master_write’:
drivers/vme/bridges/vme_tsi148.c:1352:14: warning: ‘handler’ may be used 
uninitialized in this function [-Wmaybe-uninitialized]
   if (handler->num_errors) {
              ^

This appears to be because the pointer "handler" is set and checked in 
one if statement controlled by "err_chk" and is used in a second. The 
variable "err_chk" is a kernel param and from memory this can be set at 
runtime, so there's a chance that the value of err_chk could be changed 
between the two if statements (unlikely I know, but...) resulting in 
handler being a null pointer.

Martyn

> ---
>   drivers/vme/bridges/vme_ca91cx42.c |    3 +-
>   drivers/vme/bridges/vme_tsi148.c   |   83 ++++++++++++++++----------------
>   drivers/vme/vme.c                  |   92 +++++++++++++-----------------------
>   drivers/vme/vme_bridge.h           |   23 +++++----
>   4 files changed, 91 insertions(+), 110 deletions(-)
>
> diff --git a/drivers/vme/bridges/vme_ca91cx42.c b/drivers/vme/bridges/vme_ca91cx42.c
> index f692efc..834883d 100644
> --- a/drivers/vme/bridges/vme_ca91cx42.c
> +++ b/drivers/vme/bridges/vme_ca91cx42.c
> @@ -204,8 +204,7 @@ static int ca91cx42_irq_init(struct vme_bridge *ca91cx42_bridge)
>   	/* Need pdev */
>   	pdev = container_of(ca91cx42_bridge->parent, struct pci_dev, dev);
>   
> -	/* Initialise list for VME bus errors */
> -	INIT_LIST_HEAD(&ca91cx42_bridge->vme_errors);
> +	INIT_LIST_HEAD(&ca91cx42_bridge->vme_error_handlers);
>   
>   	mutex_init(&ca91cx42_bridge->irq_mtx);
>   
> diff --git a/drivers/vme/bridges/vme_tsi148.c b/drivers/vme/bridges/vme_tsi148.c
> index 76ccfae..b0132e0 100644
> --- a/drivers/vme/bridges/vme_tsi148.c
> +++ b/drivers/vme/bridges/vme_tsi148.c
> @@ -314,8 +314,7 @@ static int tsi148_irq_init(struct vme_bridge *tsi148_bridge)
>   
>   	bridge = tsi148_bridge->driver_priv;
>   
> -	/* Initialise list for VME bus errors */
> -	INIT_LIST_HEAD(&tsi148_bridge->vme_errors);
> +	INIT_LIST_HEAD(&tsi148_bridge->vme_error_handlers);
>   
>   	mutex_init(&tsi148_bridge->irq_mtx);
>   
> @@ -1187,7 +1186,7 @@ static ssize_t tsi148_master_read(struct vme_master_resource *image, void *buf,
>   	int retval, enabled;
>   	unsigned long long vme_base, size;
>   	u32 aspace, cycle, dwidth;
> -	struct vme_bus_error *vme_err = NULL;
> +	struct vme_error_handler *handler;
>   	struct vme_bridge *tsi148_bridge;
>   	void __iomem *addr = image->kern_base + offset;
>   	unsigned int done = 0;
> @@ -1197,6 +1196,17 @@ static ssize_t tsi148_master_read(struct vme_master_resource *image, void *buf,
>   
>   	spin_lock(&image->lock);
>   
> +	if (err_chk) {
> +		__tsi148_master_get(image, &enabled, &vme_base, &size, &aspace,
> +				    &cycle, &dwidth);
> +		handler = vme_register_error_handler(tsi148_bridge, aspace,
> +						     vme_base + offset, count);
> +		if (!handler) {
> +			spin_unlock(&image->lock);
> +			return -ENOMEM;
> +		}
> +	}
> +
>   	/* The following code handles VME address alignment. We cannot use
>   	 * memcpy_xxx here because it may cut data transfers in to 8-bit
>   	 * cycles when D16 or D32 cycles are required on the VME bus.
> @@ -1240,24 +1250,16 @@ static ssize_t tsi148_master_read(struct vme_master_resource *image, void *buf,
>   out:
>   	retval = count;
>   
> -	if (!err_chk)
> -		goto skip_chk;
> -
> -	__tsi148_master_get(image, &enabled, &vme_base, &size, &aspace, &cycle,
> -		&dwidth);
> -
> -	vme_err = vme_find_error(tsi148_bridge, aspace, vme_base + offset,
> -		count);
> -	if (vme_err != NULL) {
> -		dev_err(image->parent->parent, "First VME read error detected "
> -			"an at address 0x%llx\n", vme_err->address);
> -		retval = vme_err->address - (vme_base + offset);
> -		/* Clear down save errors in this address range */
> -		vme_clear_errors(tsi148_bridge, aspace, vme_base + offset,
> -			count);
> +	if (err_chk) {
> +		if (handler->num_errors) {
> +			dev_err(image->parent->parent,
> +				"First VME read error detected an at address 0x%llx\n",
> +				handler->first_error);
> +			retval = handler->first_error - (vme_base + offset);
> +		}
> +		vme_unregister_error_handler(handler);
>   	}
>   
> -skip_chk:
>   	spin_unlock(&image->lock);
>   
>   	return retval;
> @@ -1274,7 +1276,7 @@ static ssize_t tsi148_master_write(struct vme_master_resource *image, void *buf,
>   	unsigned int done = 0;
>   	unsigned int count32;
>   
> -	struct vme_bus_error *vme_err = NULL;
> +	struct vme_error_handler *handler;
>   	struct vme_bridge *tsi148_bridge;
>   	struct tsi148_driver *bridge;
>   
> @@ -1284,6 +1286,17 @@ static ssize_t tsi148_master_write(struct vme_master_resource *image, void *buf,
>   
>   	spin_lock(&image->lock);
>   
> +	if (err_chk) {
> +		__tsi148_master_get(image, &enabled, &vme_base, &size, &aspace,
> +				    &cycle, &dwidth);
> +		handler = vme_register_error_handler(tsi148_bridge, aspace,
> +						     vme_base + offset, count);
> +		if (!handler) {
> +			spin_unlock(&image->lock);
> +			return -ENOMEM;
> +		}
> +	}
> +
>   	/* Here we apply for the same strategy we do in master_read
>   	 * function in order to assure the correct cycles.
>   	 */
> @@ -1333,30 +1346,18 @@ out:
>   	 * We check for saved errors in the written address range/space.
>   	 */
>   
> -	if (!err_chk)
> -		goto skip_chk;
> -
> -	/*
> -	 * Get window info first, to maximise the time that the buffers may
> -	 * fluch on their own
> -	 */
> -	__tsi148_master_get(image, &enabled, &vme_base, &size, &aspace, &cycle,
> -		&dwidth);
> -
> -	ioread16(bridge->flush_image->kern_base + 0x7F000);
> +	if (err_chk) {
> +		ioread16(bridge->flush_image->kern_base + 0x7F000);
>   
> -	vme_err = vme_find_error(tsi148_bridge, aspace, vme_base + offset,
> -		count);
> -	if (vme_err != NULL) {
> -		dev_warn(tsi148_bridge->parent, "First VME write error detected"
> -			" an at address 0x%llx\n", vme_err->address);
> -		retval = vme_err->address - (vme_base + offset);
> -		/* Clear down save errors in this address range */
> -		vme_clear_errors(tsi148_bridge, aspace, vme_base + offset,
> -			count);
> +		if (handler->num_errors) {
> +			dev_warn(tsi148_bridge->parent,
> +				 "First VME write error detected an at address 0x%llx\n",
> +				 handler->first_error);
> +			retval = handler->first_error - (vme_base + offset);
> +		}
> +		vme_unregister_error_handler(handler);
>   	}
>   
> -skip_chk:
>   	spin_unlock(&image->lock);
>   
>   	return retval;
> diff --git a/drivers/vme/vme.c b/drivers/vme/vme.c
> index 2b79cd2..7a10d92 100644
> --- a/drivers/vme/vme.c
> +++ b/drivers/vme/vme.c
> @@ -1026,76 +1026,52 @@ EXPORT_SYMBOL(vme_dma_free);
>   void vme_bus_error_handler(struct vme_bridge *bridge,
>   			   unsigned long long address, int am)
>   {
> -	struct vme_bus_error *error;
> -
> -	error = kmalloc(sizeof(struct vme_bus_error), GFP_ATOMIC);
> -	if (error) {
> -		error->aspace = vme_get_aspace(am);
> -		error->address = address;
> -		list_add_tail(&error->list, &bridge->vme_errors);
> -	} else {
> -		dev_err(bridge->parent,
> -			"Unable to alloc memory for VMEbus Error reporting\n");
> +	struct list_head *handler_pos = NULL;
> +	struct vme_error_handler *handler;
> +	u32 aspace = vme_get_aspace(am);
> +
> +	list_for_each(handler_pos, &bridge->vme_error_handlers) {
> +		handler = list_entry(handler_pos, struct vme_error_handler,
> +				     list);
> +		if ((aspace == handler->aspace) &&
> +		    (address >= handler->start) &&
> +		    (address < handler->end)) {
> +			if (!handler->num_errors)
> +				handler->first_error = address;
> +			if (handler->num_errors != UINT_MAX)
> +				handler->num_errors++;
> +		}
>   	}
>   }
>   EXPORT_SYMBOL(vme_bus_error_handler);
>   
> -/*
> - * Find the first error in this address range
> - */
> -struct vme_bus_error *vme_find_error(struct vme_bridge *bridge, u32 aspace,
> -				     unsigned long long address, size_t count)
> +struct vme_error_handler *vme_register_error_handler(
> +	struct vme_bridge *bridge, u32 aspace,
> +	unsigned long long address, size_t len)
>   {
> -	struct list_head *err_pos;
> -	struct vme_bus_error *vme_err, *valid = NULL;
> -	unsigned long long bound;
> -
> -	bound = address + count;
> +	struct vme_error_handler *handler;
>   
> -	err_pos = NULL;
> -	/* Iterate through errors */
> -	list_for_each(err_pos, &bridge->vme_errors) {
> -		vme_err = list_entry(err_pos, struct vme_bus_error, list);
> -		if ((vme_err->aspace == aspace) &&
> -		    (vme_err->address >= address) &&
> -		    (vme_err->address < bound)) {
> +	handler = kmalloc(sizeof(*handler), GFP_KERNEL);
> +	if (!handler)
> +		return NULL;
>   
> -			valid = vme_err;
> -			break;
> -		}
> -	}
> +	handler->aspace = aspace;
> +	handler->start = address;
> +	handler->end = address + len;
> +	handler->num_errors = 0;
> +	handler->first_error = 0;
> +	list_add_tail(&handler->list, &bridge->vme_error_handlers);
>   
> -	return valid;
> +	return handler;
>   }
> -EXPORT_SYMBOL(vme_find_error);
> +EXPORT_SYMBOL(vme_register_error_handler);
>   
> -/*
> - * Clear errors in the provided address range.
> - */
> -void vme_clear_errors(struct vme_bridge *bridge, u32 aspace,
> -		      unsigned long long address, size_t count)
> +void vme_unregister_error_handler(struct vme_error_handler *handler)
>   {
> -	struct list_head *err_pos, *temp;
> -	struct vme_bus_error *vme_err;
> -	unsigned long long bound;
> -
> -	bound = address + count;
> -
> -	err_pos = NULL;
> -	/* Iterate through errors */
> -	list_for_each_safe(err_pos, temp, &bridge->vme_errors) {
> -		vme_err = list_entry(err_pos, struct vme_bus_error, list);
> -
> -		if ((vme_err->aspace == aspace) &&
> -		    (vme_err->address >= address) &&
> -		    (vme_err->address < bound)) {
> -
> -			list_del(err_pos);
> -			kfree(vme_err);
> -		}
> -	}
> +	list_del(&handler->list);
> +	kfree(handler);
>   }
> -EXPORT_SYMBOL(vme_clear_errors);
> +EXPORT_SYMBOL(vme_unregister_error_handler);
>   
>   void vme_irq_handler(struct vme_bridge *bridge, int level, int statid)
>   {
> diff --git a/drivers/vme/vme_bridge.h b/drivers/vme/vme_bridge.h
> index 92fbe18..397578a 100644
> --- a/drivers/vme/vme_bridge.h
> +++ b/drivers/vme/vme_bridge.h
> @@ -75,10 +75,13 @@ struct vme_lm_resource {
>   	int monitors;
>   };
>   
> -struct vme_bus_error {
> +struct vme_error_handler {
>   	struct list_head list;
> -	u32 aspace;
> -	unsigned long long address;
> +	unsigned long long start;	/* Beginning of error window */
> +	unsigned long long end;		/* End of error window */
> +	unsigned long long first_error;	/* Address of the first error */
> +	u32 aspace;			/* Address space of error window*/
> +	unsigned num_errors;		/* Number of errors */
>   };
>   
>   struct vme_callback {
> @@ -106,8 +109,10 @@ struct vme_bridge {
>   	struct list_head dma_resources;
>   	struct list_head lm_resources;
>   
> -	struct list_head vme_errors;	/* List for errors generated on VME */
> -	struct list_head devices;	/* List of devices on this bridge */
> +	/* List for registered errors handlers */
> +	struct list_head vme_error_handlers;
> +	/* List of devices on this bridge */
> +	struct list_head devices;
>   
>   	/* Bridge Info - XXX Move to private structure? */
>   	struct device *parent;	/* Parent device (eg. pdev->dev for PCI) */
> @@ -168,13 +173,13 @@ struct vme_bridge {
>   
>   void vme_bus_error_handler(struct vme_bridge *bridge,
>   			   unsigned long long address, int am);
> -struct vme_bus_error *vme_find_error(struct vme_bridge *bridge, u32 aspace,
> -				     unsigned long long address, size_t count);
> -void vme_clear_errors(struct vme_bridge *bridge, u32 aspace,
> -		      unsigned long long address, size_t count);
>   void vme_irq_handler(struct vme_bridge *, int, int);
>   
>   int vme_register_bridge(struct vme_bridge *);
>   void vme_unregister_bridge(struct vme_bridge *);
> +struct vme_error_handler *vme_register_error_handler(
> +	struct vme_bridge *bridge, u32 aspace,
> +	unsigned long long address, size_t len);
> +void vme_unregister_error_handler(struct vme_error_handler *handler);
>   
>   #endif /* _VME_BRIDGE_H_ */

_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel