padata: set cpu_index of unused CPUs to -1

commit 1bd845bcb41d5b7f83745e0cb99273eb376f2ec5 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/kernel/padata.c b/kernel/padata.c
index 8b95e318408d2370ab0f4419559d81dbaf9a4e76..26feec13f0283f0ad3eef8ec17bc3f658f20accf 100644 (file)
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -395,8 +395,14 @@ 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++;