On Mon, 8 Jun 2015 14:13:17 -0400 (EDT)
Dave Anderson <anderson@xxxxxxxxxx> wrote:
>
>
> ----- Original Message -----
> > The kernel commit 2f859d0dad8 ("s390/smp: reduce size of struct pcpu")
> > for linux-4.0 removed the "async_stack" and "panic_stack" members from
> > "struct pcpu".
> >
> > So now the only option to find out the stack address is using "struct
> > lowcore" (again). Unfortunately we don't get the exact address because
> > since commit dc7ee00d477 ("s390: lowcore stack pointer offsets") the stack
> > frame overhead is already subtracted from the addresses. Therefore we
> > have to roundup the stack address to PAGE_SIZE.
> >
> > Signed-off-by: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
>
> Hi Michael,
>
> For the changelog -- what's the symptom of the failure?
Hi Dave,
Here the symptom description:
Backtraces (e.g. bt -a) for active tasks that execute I/O or machine check
interrupts are not printed and for "normal" task backtraces ugly messages like
"bt: invalid kernel virtual address: 100000180000088 type: "readmem_ul""
are shown.
Michael
>
> Dave
>
> > ---
> > s390x.c | 7 +++----
> > 1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > --- a/s390x.c
> > +++ b/s390x.c
> > @@ -1027,8 +1027,6 @@ static unsigned long get_int_stack_pcpu(
> > {
> > unsigned long addr;
> >
> > - if (!MEMBER_EXISTS("pcpu", stack_name))
> > - return 0;
> > addr = symbol_value("pcpu_devices") +
> > cpu * STRUCT_SIZE("pcpu") + MEMBER_OFFSET("pcpu", stack_name);
> > return readmem_ul(addr) + INT_STACK_SIZE;
> > @@ -1041,7 +1039,8 @@ static unsigned long get_int_stack_lc(ch
> > {
> > if (!MEMBER_EXISTS(lc_struct, stack_name))
> > return 0;
> > - return ULONG(lc + MEMBER_OFFSET(lc_struct, stack_name));
> > + return roundup(ULONG(lc + MEMBER_OFFSET(lc_struct, stack_name)),
> > + PAGESIZE());
> > }
> >
> > /*
> > @@ -1057,7 +1056,7 @@ static void get_int_stack(char *stack_na
> > stack_addr = symbol_value("restart_stack");
> > stack_addr = readmem_ul(stack_addr);
> > } else {
> > - if (symbol_exists("pcpu_devices"))
> > + if (symbol_exists("pcpu_devices") && MEMBER_EXISTS("pcpu", stack_name))
> > stack_addr = get_int_stack_pcpu(stack_name, cpu);
> > else
> > stack_addr = get_int_stack_lc(stack_name, lc);
> >
>
--
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