Re: 2.6.29 acpi regression: acpi_ex_extract_from_field -- div by zero

Lin Ming
2009-03-16T03:51:21Z

> Hi,
>
> sometimes, when booting up/resuming from disk, I get an oops[1].
>
> obj_desc->common_field.access_bit_width is zero, but even after the
> loop. Division before the loop is apparently OK.

Would please try below debug patch to see which region filed is
accessed?

diff --git a/drivers/acpi/acpica/exfldio.c b/drivers/acpi/acpica/exfldio.c
index ef58ac4..10ac0c8 100644
--- a/drivers/acpi/acpica/exfldio.c
+++ b/drivers/acpi/acpica/exfldio.c
@@ -683,6 +683,7 @@ acpi_ex_extract_from_field(union acpi_operand_object *obj_desc,
u32 datum_count;
u32 field_datum_count;
u32 i;
+ struct acpi_buffer name_buffer = { ACPI_ALLOCATE_BUFFER, NULL };

ACPI_FUNCTION_TRACE(ex_extract_from_field);

@@ -765,6 +766,20 @@ acpi_ex_extract_from_field(union acpi_operand_object *obj_desc,
raw_datum >> obj_desc->common_field.start_field_bit_offset;
}

+ if (obj_desc->common_field.bit_length == 0 ||
+ obj_desc->common_field.access_bit_width == 0) {
+ status = acpi_get_name(obj_desc->common_field.node,
+ ACPI_FULL_PATHNAME, &name_buffer);
+ if (ACPI_FAILURE(status)) {
+ printk(KERN_DEBUG "ACPI Debug: %s\n",
+ acpi_format_exception(status));
+ } else {
+ printk(KERN_DEBUG "ACPI Debug: field node path: %s\n",
+ (char *) name_buffer.pointer);
+ kfree(name_buffer.pointer);
+ }
+ }
+
/* Mask off any extra bits in the last datum */

buffer_tail_bits = obj_desc->common_field.bit_length %

---
Lin Ming

>
> This is the case:
> /* Mask off any extra bits in the last datum */
>
> buffer_tail_bits = obj_desc->common_field.bit_length %
> obj_desc->common_field.access_bit_width;
>
> .L39:
> xorl %edx, %edx #
> movzbl 37(%rbx), %esi #
> <variable>.common_field.access_bit_width,
> <variable>.common_field.access_bit_width
> movl 24(%rbx), %eax # <variable>.common_field.bit_length,
> <variable>.common_field.bit_length
> --------------- here:
> divl %esi # <variable>.common_field.access_bit_width
> movl %edx, %ecx #, tmp121
> testl %edx, %edx # tmp121
> je .L41 #,
>
> [1] http://www.fi.muni.cz/~xslaby/sklad/panics/acpi_oops.png
> --