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SubjectRe: [PATCH 2/3] staging: greybus: loopback.c: do insertion in O(n) instead of O(n lg n)
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On 2018-10-11 01:03, Bryan O'Donoghue wrote:
> On 05/10/2018 15:28, Rasmus Villemoes wrote:
>> Signed-off-by: Rasmus Villemoes<linux@rasmusvillemoes.dk>
>> ---
>> I have no idea if the performance matters (it probably doesn't). Feel
>> free to ignore this and the followup cleanup.
>
> What's the problem you're fixing here ?
>
> Is it tested ?

I got curious why one would want to keep a linked list sorted in the
first place (it can't be for doing binary searches). But it seems that
gb_loopback_device::list is unused, along with the list_op_async. Given
that the below compiles, doesn't that prove that the code is
dead/unused, or what am I missing?

diff --git a/drivers/staging/greybus/loopback.c
b/drivers/staging/greybus/loopback.c
index 7080294f705c..e4d42c1dc284 100644
--- a/drivers/staging/greybus/loopback.c
+++ b/drivers/staging/greybus/loopback.c
@@ -47,8 +47,6 @@ struct gb_loopback_device {

/* We need to take a lock in atomic context */
spinlock_t lock;
- struct list_head list;
- struct list_head list_op_async;
wait_queue_head_t wq;
};

@@ -68,7 +66,6 @@ struct gb_loopback {
struct kfifo kfifo_lat;
struct mutex mutex;
struct task_struct *task;
- struct list_head entry;
struct device *dev;
wait_queue_head_t wq;
wait_queue_head_t wq_completion;
@@ -987,37 +984,6 @@ static const struct file_operations
gb_loopback_debugfs_latency_ops = {
.release = single_release,
};

-static int gb_loopback_bus_id_compare(void *priv, struct list_head *lha,
- struct list_head *lhb)
-{
- struct gb_loopback *a = list_entry(lha, struct gb_loopback, entry);
- struct gb_loopback *b = list_entry(lhb, struct gb_loopback, entry);
- struct gb_connection *ca = a->connection;
- struct gb_connection *cb = b->connection;
-
- if (ca->bundle->intf->interface_id < cb->bundle->intf->interface_id)
- return -1;
- if (cb->bundle->intf->interface_id < ca->bundle->intf->interface_id)
- return 1;
- if (ca->bundle->id < cb->bundle->id)
- return -1;
- if (cb->bundle->id < ca->bundle->id)
- return 1;
- if (ca->intf_cport_id < cb->intf_cport_id)
- return -1;
- else if (cb->intf_cport_id < ca->intf_cport_id)
- return 1;
-
- return 0;
-}
-
-static void gb_loopback_insert_id(struct gb_loopback *gb)
-{
- /* perform an insertion sort */
- list_add_tail(&gb->entry, &gb_dev.list);
- list_sort(NULL, &gb_dev.list, gb_loopback_bus_id_compare);
-}
-
#define DEBUGFS_NAMELEN 32

static int gb_loopback_probe(struct gb_bundle *bundle,
@@ -1113,7 +1079,6 @@ static int gb_loopback_probe(struct gb_bundle *bundle,
}

spin_lock_irqsave(&gb_dev.lock, flags);
- gb_loopback_insert_id(gb);
gb_dev.count++;
spin_unlock_irqrestore(&gb_dev.lock, flags);

@@ -1169,7 +1134,6 @@ static void gb_loopback_disconnect(struct
gb_bundle *bundle)

spin_lock_irqsave(&gb_dev.lock, flags);
gb_dev.count--;
- list_del(&gb->entry);
spin_unlock_irqrestore(&gb_dev.lock, flags);

device_unregister(gb->dev);
@@ -1196,8 +1160,6 @@ static int loopback_init(void)
{
int retval;

- INIT_LIST_HEAD(&gb_dev.list);
- INIT_LIST_HEAD(&gb_dev.list_op_async);
spin_lock_init(&gb_dev.lock);
gb_dev.root = debugfs_create_dir("gb_loopback", NULL);
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