Re: [Crash-utility] 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