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Subject[PATCH 6/8] padata: Use a timer to handle the reorder queues
padata_get_next had a bogus check that returned always true,
so the try_again loop in padata_reorder was never taken.
This can lead to object leaks in some rare cases. This patch
implements a timer that processes the reorder queues if noone
else does it in appropriate time.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
---
include/linux/padata.h | 2 ++
kernel/padata.c | 25 ++++++++++++++++++-------
2 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/include/linux/padata.h b/include/linux/padata.h
index 51611da..64836a6 100644
--- a/include/linux/padata.h
+++ b/include/linux/padata.h
@@ -24,6 +24,7 @@
#include <linux/workqueue.h>
#include <linux/spinlock.h>
#include <linux/list.h>
+#include <linux/timer.h>

struct padata_priv {
struct list_head list;
@@ -60,6 +61,7 @@ struct parallel_data {
unsigned int max_seq_nr;
cpumask_var_t cpumask;
spinlock_t lock;
+ struct timer_list timer;
};

struct padata_instance {
diff --git a/kernel/padata.c b/kernel/padata.c
index 82958e0..6d7ea48 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -231,7 +231,8 @@ static struct padata_priv *padata_get_next(struct parallel_data *pd)
goto out;
}

- if (next_nr % num_cpus == next_queue->cpu_index) {
+ queue = per_cpu_ptr(pd->queue, smp_processor_id());
+ if (queue->cpu_index == next_queue->cpu_index) {
padata = ERR_PTR(-ENODATA);
goto out;
}
@@ -247,9 +248,8 @@ static void padata_reorder(struct parallel_data *pd)
struct padata_queue *queue;
struct padata_instance *pinst = pd->pinst;

-try_again:
if (!spin_trylock_bh(&pd->lock))
- goto out;
+ return;

while (1) {
padata = padata_get_next(pd);
@@ -258,8 +258,9 @@ try_again:
break;

if (PTR_ERR(padata) == -ENODATA) {
+ del_timer(&pd->timer);
spin_unlock_bh(&pd->lock);
- goto out;
+ return;
}

queue = per_cpu_ptr(pd->queue, padata->cb_cpu);
@@ -273,13 +274,22 @@ try_again:

spin_unlock_bh(&pd->lock);

- if (atomic_read(&pd->reorder_objects))
- goto try_again;
+ if (atomic_read(&pd->reorder_objects)
+ && !(pinst->flags & PADATA_RESET))
+ mod_timer(&pd->timer, jiffies + HZ);
+ else
+ del_timer(&pd->timer);

-out:
return;
}

+static void padata_reorder_timer(unsigned long arg)
+{
+ struct parallel_data *pd = (struct parallel_data *)arg;
+
+ padata_reorder(pd);
+}
+
static void padata_serial_worker(struct work_struct *work)
{
struct padata_queue *queue;
@@ -383,6 +393,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
num_cpus = cpumask_weight(pd->cpumask);
pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1;

+ setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd);
atomic_set(&pd->seq_nr, -1);
atomic_set(&pd->reorder_objects, 0);
atomic_set(&pd->refcnt, 0);
--
1.5.6.5


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