3.16.84-rc1 review patch. If anyone has any objections, please let me know.
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From: Herbert Xu herbert@gondor.apana.org.au
commit 07928d9bfc81640bab36f5190e8725894d93b659 upstream.
The function padata_flush_queues is fundamentally broken because it cannot force padata users to complete the request that is underway. IOW padata has to passively wait for the completion of any outstanding work.
As it stands flushing is used in two places. Its use in padata_stop is simply unnecessary because nothing depends on the queues to be flushed afterwards.
The other use in padata_replace is more substantial as we depend on it to free the old pd structure. This patch instead uses the pd->refcnt to dynamically free the pd structure once all requests are complete.
Fixes: 2b73b07ab8a4 ("padata: Flush the padata queues actively") Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Reviewed-by: Daniel Jordan daniel.m.jordan@oracle.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/kernel/padata.c +++ b/kernel/padata.c @@ -33,6 +33,8 @@
#define MAX_OBJ_NUM 1000
+static void padata_free_pd(struct parallel_data *pd); + static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) { int cpu, target_cpu; @@ -281,6 +283,7 @@ static void padata_serial_worker(struct struct padata_serial_queue *squeue; struct parallel_data *pd; LIST_HEAD(local_list); + int cnt;
local_bh_disable(); squeue = container_of(serial_work, struct padata_serial_queue, work); @@ -290,6 +293,8 @@ static void padata_serial_worker(struct list_replace_init(&squeue->serial.list, &local_list); spin_unlock(&squeue->serial.lock);
+ cnt = 0; + while (!list_empty(&local_list)) { struct padata_priv *padata;
@@ -299,9 +304,12 @@ static void padata_serial_worker(struct list_del_init(&padata->list);
padata->serial(padata); - atomic_dec(&pd->refcnt); + cnt++; } local_bh_enable(); + + if (atomic_sub_and_test(cnt, &pd->refcnt)) + padata_free_pd(pd); }
/** @@ -432,7 +440,7 @@ static struct parallel_data *padata_allo padata_init_squeues(pd); atomic_set(&pd->seq_nr, -1); atomic_set(&pd->reorder_objects, 0); - atomic_set(&pd->refcnt, 0); + atomic_set(&pd->refcnt, 1); pd->pinst = pinst; spin_lock_init(&pd->lock); pd->cpu = cpumask_first(pd->cpumask.pcpu); @@ -459,29 +467,6 @@ static void padata_free_pd(struct parall kfree(pd); }
-/* Flush all objects out of the padata queues. */ -static void padata_flush_queues(struct parallel_data *pd) -{ - int cpu; - struct padata_parallel_queue *pqueue; - struct padata_serial_queue *squeue; - - for_each_cpu(cpu, pd->cpumask.pcpu) { - pqueue = per_cpu_ptr(pd->pqueue, cpu); - flush_work(&pqueue->work); - } - - if (atomic_read(&pd->reorder_objects)) - padata_reorder(pd); - - for_each_cpu(cpu, pd->cpumask.cbcpu) { - squeue = per_cpu_ptr(pd->squeue, cpu); - flush_work(&squeue->work); - } - - BUG_ON(atomic_read(&pd->refcnt) != 0); -} - static void __padata_start(struct padata_instance *pinst) { pinst->flags |= PADATA_INIT; @@ -495,10 +480,6 @@ static void __padata_stop(struct padata_ pinst->flags &= ~PADATA_INIT;
synchronize_rcu(); - - get_online_cpus(); - padata_flush_queues(pinst->pd); - put_online_cpus(); }
/* Replace the internal control structure with a new one. */ @@ -519,8 +500,8 @@ static void padata_replace(struct padata if (!cpumask_equal(pd_old->cpumask.cbcpu, pd_new->cpumask.cbcpu)) notification_mask |= PADATA_CPU_SERIAL;
- padata_flush_queues(pd_old); - padata_free_pd(pd_old); + if (atomic_dec_and_test(&pd_old->refcnt)) + padata_free_pd(pd_old);
if (notification_mask) blocking_notifier_call_chain(&pinst->cpumask_change_notifier,