[RESEND 3/4] vme: change bus error handling scheme
Dmitry Kalinkin
dmitry.kalinkin at gmail.com
Mon Sep 21 15:26:22 UTC 2015
> On 18 Sep 2015, at 05:46, Martyn Welch <martyn at welchs.me.uk> wrote:
>
>
>
> On 18/09/15 00:01, dmitry.kalinkin at gmail.com wrote:
>> From: Dmitry Kalinkin <dmitry.kalinkin at gmail.com>
>>
>> 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 at gmail.com>
>> Cc: Igor Alekseev <igor.alekseev at itep.ru>
>
> 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) {
> ^
I can’t reproduce this warning on gcc version 4.7.2. And now that I think about it, gcc would not give this warning because of the possible race condition. It will assume that err_chk stays constant.
>
> 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_ */
>
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