cpumask: fix Powerpc panic() caused by cpumask:smp_call_function_many Stephen Rothwell got this panic: Kernel panic - not syncing: bad return code qirr - rc = fffffffffffffffc ... [c0000000bce4b560] [c00000000005dcd8] .panic+0x88/0x1d0 [c0000000bce4b610] [c000000000040e28] .smp_xics_message_pass+0xf8/0x230 [c0000000bce4b6b0] [c00000000002b0f0] .arch_send_call_function_ipi+0x60/0xb0 [c0000000bce4b740] [c00000000008d64c] .smp_call_function_many+0x20c/0x360 [c0000000bce4b810] [c00000000008d7d8] .smp_call_function+0x38/0x50 [c0000000bce4b890] [c000000000064e44] .on_each_cpu+0x24/0x90 [c0000000bce4b930] [c0000000001230c4] .invalidate_bh_lrus+0x24/0x40 [c0000000bce4b9b0] [c00000000012b3b4] .kill_bdev+0x34/0x60 The rc = fffffffffffffffc is an error code from the hypervisor and means "bad parameter". This is caused by PowerPC's arch_send_call_function_ipi using for_each_cpu_mask(), which iterates to NR_CPUS not nr_cpu_ids, and the upper bits of the cpumask are undefined (and eventually won't be allocated). So we zero those bits explicitly until all the kernel iterators are converted (which will be a while yet). Signed-off-by: Rusty Russell --- kernel/smp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/smp.c b/kernel/smp.c --- a/kernel/smp.c +++ b/kernel/smp.c @@ -329,6 +329,8 @@ void smp_call_function_many(const struct data->csd.flags |= CSD_FLAG_WAIT; data->csd.func = func; data->csd.info = info; + /* FIXME: Make archs use new iterators and ignore bits >= nr_cpu_ids */ + memset(to_cpumask(data->cpumask_bits), 0, cpumask_size()); cpumask_and(to_cpumask(data->cpumask_bits), mask, cpu_online_mask); cpumask_clear_cpu(smp_processor_id(), to_cpumask(data->cpumask_bits)); data->refs = cpumask_weight(to_cpumask(data->cpumask_bits));