padata: set cpu_index of unused CPUs to -1

The parallel queue per-cpu data structure gets initialized only for CPUs
in the 'pcpu' CPU mask set. This is not sufficient as the reorder timer
may run on a different CPU and might wrongly decide it's the target CPU
for the next reorder item as per-cpu memory gets memset(0) and we might
be waiting for the first CPU in cpumask.pcpu, i.e. cpu_index 0.

Make the '__this_cpu_read(pd->pqueue->cpu_index) == next_queue->cpu_index'
compare in padata_get_next() fail in this case by initializing the
cpu_index member of all per-cpu parallel queues. Use -1 for unused ones.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 7 insertions, 1 deletions

diff --git a/kernel/padata.c b/kernel/padata.c
index 868f947166d7..1b9b4bac4a9b 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -384,8 +384,14 @@ static void padata_init_pqueues(struct parallel_data *pd)
         struct padata_parallel_queue *pqueue;
 
         cpu_index = 0;
-        for_each_cpu(cpu, pd->cpumask.pcpu) {
+        for_each_possible_cpu(cpu) {
                 pqueue = per_cpu_ptr(pd->pqueue, cpu);
+
+                if (!cpumask_test_cpu(cpu, pd->cpumask.pcpu)) {
+                        pqueue->cpu_index = -1;
+                        continue;
+                }
+
                 pqueue->pd = pd;
                 pqueue->cpu_index = cpu_index;
                 cpu_index++;