9:32 a.m.
Sachin,
This may require help from the IBM ppc64 people out there,
but it appears that the issue at hand has something to do
with the uniprocessor aspect.
Your vmlinux is an SMP kernel, but I'm guessing that the wrong
choice of "runq" addresses is being made below:
if (symbol_exists("per_cpu__runqueues") &&
VALID_MEMBER(runqueue_idle)) {
runqbuf = GETBUF(SIZE(runqueue));
for (i = 0; i < nr_cpus; i++) {
if ((kt->flags & SMP) && (kt->flags &
PER_CPU_OFF)) {
runq = symbol_value("per_cpu__runqueues") +
kt->__per_cpu_offset[i];
} else
runq = symbol_value("per_cpu__runqueues");
readmem(runq, KVADDR, runqbuf,
SIZE(runqueue), "runqueues entry (per_cpu)",
FAULT_ON_ERROR);
tasklist[i] = ULONG(runqbuf + OFFSET(runqueue_idle));
if (IS_KVADDR(tasklist[i]))
cnt++;
I don't know what your "kt->flags" is showing at the
decision point above, but if you hack the code and force
it to select the "other" runq value, does it work OK?
When CONFIG_SMP is not configured into the kernel, then
the direct value of "per_cpu__runqueues" is used, whereas
with SMP kernels, the appropriate offset needs to be
applied. At least that's how it works (has worked?) with
the other architectures.
Dave
9:47 a.m.
New subject: crash: cannot resolve "init_task_union"
Dave Anderson wrote:
Sachin,
This may require help from the IBM ppc64 people out there,
but it appears that the issue at hand has something to do
with the uniprocessor aspect.
Your vmlinux is an SMP kernel, but I'm guessing that the wrong
choice of "runq" addresses is being made below:
if (symbol_exists("per_cpu__runqueues") &&
VALID_MEMBER(runqueue_idle)) {
runqbuf = GETBUF(SIZE(runqueue));
for (i = 0; i < nr_cpus; i++) {
if ((kt->flags & SMP) && (kt->flags &
PER_CPU_OFF)) {
runq = symbol_value("per_cpu__runqueues") +
kt->__per_cpu_offset[i];
} else
runq = symbol_value("per_cpu__runqueues");
readmem(runq, KVADDR, runqbuf,
SIZE(runqueue), "runqueues entry (per_cpu)",
FAULT_ON_ERROR);
tasklist[i] = ULONG(runqbuf + OFFSET(runqueue_idle));
if (IS_KVADDR(tasklist[i]))
cnt++;
I don't know what your "kt->flags" is showing at the
decision point above, but if you hack the code and force
it to select the "other" runq value, does it work OK?
When CONFIG_SMP is not configured into the kernel, then
the direct value of "per_cpu__runqueues" is used, whereas
with SMP kernels, the appropriate offset needs to be
applied. At least that's how it works (has worked?) with
the other architectures.
Dave
Looking at ppc64_paca_init(), it appears that this might be
the problem if SMP is not set in kt->flags:
static void
ppc64_paca_init()
{
...
for (i = cpus = 0; i < nr_paca; i++) {
div_t val = div(i, BITS_FOR_LONG);
/*
* CPU online?
*/
if (!(cpu_online_map[val.quot] & (0x1UL << val.rem)))
continue;
readmem(symbol_value("paca") + (i * SIZE(ppc64_paca)),
KVADDR, cpu_paca_buf, SIZE(ppc64_paca),
"paca entry", FAULT_ON_ERROR);
kt->__per_cpu_offset[i] = ULONG(cpu_paca_buf + data_offset);
kt->flags |= PER_CPU_OFF;
cpus++;
}
kt->cpus = cpus;
if (kt->cpus > 1)
kt->flags |= SMP;
}
If SMP is not set coming into this function, and therefore won't
get set above, then the wrong runq pointer would be selected later
on get_idle_threads().
Dave
10:07 a.m.
New subject: crash: cannot resolve "init_task_union"
Dave Anderson wrote:
Dave Anderson wrote:
>
> Sachin,
>
> This may require help from the IBM ppc64 people out there,
> but it appears that the issue at hand has something to do
> with the uniprocessor aspect.
>
> Your vmlinux is an SMP kernel, but I'm guessing that the wrong
> choice of "runq" addresses is being made below:
>
> if (symbol_exists("per_cpu__runqueues") &&
> VALID_MEMBER(runqueue_idle)) {
> runqbuf = GETBUF(SIZE(runqueue));
> for (i = 0; i < nr_cpus; i++) {
> if ((kt->flags & SMP) && (kt->flags &
PER_CPU_OFF)) {
> runq = symbol_value("per_cpu__runqueues")
+
> kt->__per_cpu_offset[i];
> } else
> runq = symbol_value("per_cpu__runqueues");
>
> readmem(runq, KVADDR, runqbuf,
> SIZE(runqueue), "runqueues entry
(per_cpu)",
> FAULT_ON_ERROR);
> tasklist[i] = ULONG(runqbuf + OFFSET(runqueue_idle));
> if (IS_KVADDR(tasklist[i]))
> cnt++;
>
> I don't know what your "kt->flags" is showing at the
> decision point above, but if you hack the code and force
> it to select the "other" runq value, does it work OK?
>
> When CONFIG_SMP is not configured into the kernel, then
> the direct value of "per_cpu__runqueues" is used, whereas
> with SMP kernels, the appropriate offset needs to be
> applied. At least that's how it works (has worked?) with
> the other architectures.
>
> Dave
Looking at ppc64_paca_init(), it appears that this might be
the problem if SMP is not set in kt->flags:
static void
ppc64_paca_init()
{
...
for (i = cpus = 0; i < nr_paca; i++) {
div_t val = div(i, BITS_FOR_LONG);
/*
* CPU online?
*/
if (!(cpu_online_map[val.quot] & (0x1UL << val.rem)))
continue;
readmem(symbol_value("paca") + (i * SIZE(ppc64_paca)),
KVADDR, cpu_paca_buf, SIZE(ppc64_paca),
"paca entry", FAULT_ON_ERROR);
kt->__per_cpu_offset[i] = ULONG(cpu_paca_buf + data_offset);
kt->flags |= PER_CPU_OFF;
cpus++;
}
kt->cpus = cpus;
if (kt->cpus > 1)
kt->flags |= SMP;
}
If SMP is not set coming into this function, and therefore won't
get set above, then the wrong runq pointer would be selected later
on get_idle_threads().
Dave
And then there's this code in kernel_init():
if ((sp1 = symbol_search("__per_cpu_start")) &&
(sp2 = symbol_search("__per_cpu_end")) &&
(sp1->type == 'A') && (sp2->type == 'A')
&&
(sp2->value > sp1->value))
kt->flags |= SMP|PER_CPU_OFF;
On a RHEL5 x86_64:
crash> sym -q __per_cpu_ | grep -e start -e end
ffffffff80603000 (A) __per_cpu_start
ffffffff80607288 (A) __per_cpu_end
crash>
On a RHEL5 x86:
crash> sym -q __per_cpu | grep -e start -e end
c03100a0 (A) __per_cpu_start
c0315ae4 (A) __per_cpu_end
crash>
But on your RHEL5 ppc64 kernel:
# nm -Bn vmlinux | grep __per_cpu
c000000000430100 D __per_cpu_start
c0000000004356f0 D __per_cpu_end
#
So if you remove the two "type == 'A'" qualifiers
from the if statement above, does it work OK?
Dave
11:38 p.m.
New subject: crash: cannot resolve "init_task_union"
Dave Anderson wrote:
On a RHEL5 x86:
crash> sym -q __per_cpu | grep -e start -e end
c03100a0 (A) __per_cpu_start
c0315ae4 (A) __per_cpu_end
crash>
But on your RHEL5 ppc64 kernel:
# nm -Bn vmlinux | grep __per_cpu
c000000000430100 D __per_cpu_start
c0000000004356f0 D __per_cpu_end
#
So if you remove the two "type == 'A'" qualifiers
from the if statement above, does it work OK?
Dave , thanks for the hint. Yes these symbols are of
type D on PPC64 machine. Infact after checking on latest
RHEL5 kernels [ with relocatable support ] this is
the case with even other archs also.
[root@llm19 boot]# cat System.map-2.6.18-1.2767.el5 | grep __per_cpu_
c065dd2c r __ksymtab___per_cpu_offset
c0663c64 r __kcrctab___per_cpu_offset
c0666c12 r __kstrtab___per_cpu_offset
c06e6b80 D __per_cpu_offset
c077d100 D __per_cpu_start
c0781de4 D __per_cpu_end
[root@llm19 boot]# uname -i
i386
[root@llm19 boot]#
So this probably can be a generic problem affecting other arch's
also.
Thanks for the help.
Attached here is a patch to fix this problem. Let me know if it's
ok.
Thanks
-Sachin
* On a UP machine running SMP kernel, crash fails while reading idle tasks
* from per cpu data.
Signed-off-by : Sachin Sant <sachinp(a)in.ibm.com>
---
8:30 a.m.
New subject: crash: cannot resolve "init_task_union"
"Sachin P. Sant" wrote:
Dave Anderson wrote:
> On a RHEL5 x86:
>
> crash> sym -q __per_cpu | grep -e start -e end
> c03100a0 (A) __per_cpu_start
> c0315ae4 (A) __per_cpu_end
> crash>
>
> But on your RHEL5 ppc64 kernel:
>
> # nm -Bn vmlinux | grep __per_cpu
> c000000000430100 D __per_cpu_start
> c0000000004356f0 D __per_cpu_end
> #
>
> So if you remove the two "type == 'A'" qualifiers
> from the if statement above, does it work OK?
>
Dave , thanks for the hint. Yes these symbols are of
type D on PPC64 machine. Infact after checking on latest
RHEL5 kernels [ with relocatable support ] this is
the case with even other archs also.
[root@llm19 boot]# cat System.map-2.6.18-1.2767.el5 | grep __per_cpu_
c065dd2c r __ksymtab___per_cpu_offset
c0663c64 r __kcrctab___per_cpu_offset
c0666c12 r __kstrtab___per_cpu_offset
c06e6b80 D __per_cpu_offset
c077d100 D __per_cpu_start
c0781de4 D __per_cpu_end
[root@llm19 boot]# uname -i
i386
[root@llm19 boot]#
Yes, you are right -- I was looking at a much earlier
RHEL5 dumpfile...
So this probably can be a generic problem affecting other arch's
also.
Thanks for the help.
Attached here is a patch to fix this problem. Let me know if it's
ok.
Thanks
-Sachin
Looks good -- queued for the next release.
Thanks,
Dave
* On a UP machine running SMP kernel, crash fails while reading idle
tasks
* from per cpu data.
Signed-off-by : Sachin Sant <sachinp(a)in.ibm.com>
---
------------------------------------------------------------------------------------------------------------------------
* On a UP machine running SMP kernel, crash fails while reading idle tasks
* from per cpu data.
Signed-off-by : Sachin Sant <sachinp(a)in.ibm.com>
---
diff -Naurp crash-4.0-3.16/kernel.c crash-4.0-3.16-new/kernel.c
--- crash-4.0-3.16/kernel.c 2006-12-22 01:24:11.000000000 +0530
+++ crash-4.0-3.16-new/kernel.c 2007-01-05 10:49:39.000000000 +0530
@@ -114,7 +114,8 @@ kernel_init()
if ((sp1 = symbol_search("__per_cpu_start")) &&
(sp2 = symbol_search("__per_cpu_end")) &&
- (sp1->type == 'A') && (sp2->type == 'A')
&&
+ (sp1->type == 'A' || sp1->type == 'D') &&
+ (sp2->type == 'A' || sp2->type == 'D') &&
(sp2->value > sp1->value))
kt->flags |= SMP|PER_CPU_OFF;
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4 comments
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participants (2)
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Dave Anderson -
Sachin P. Sant