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greybus: loopback: Convert cross-thread mutex to spinlock while relaxing connect locks 

This patch converts the cross-thread mutex used to synchronize threads with
respect to each other to a spinlock. This is done to enable taking of locks
in the following patches while in atomic context. A small re-order of
locking in connection setup/tear-down is done to minimize the amount of
time spent in spinlock_irqsave().

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Bryan O'Donoghue 2015-12-07 01:59:05 +00:00 committed by Greg Kroah-Hartman
parent b933fa4a40
commit 2e238d71ed
1 changed files with 17 additions and 11 deletions
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28
drivers/staging/greybus/loopback.c
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@ -19,6 +19,7 @@
#include <linux/kfifo.h>
#include <linux/debugfs.h>
#include <linux/list_sort.h>
#include <linux/spinlock.h>
#include <asm/div64.h>
@ -39,7 +40,8 @@ struct gb_loopback_device {
u32 count;
size_t size_max;
struct mutex mutex;
/* We need to take a lock in atomic context */
spinlock_t lock;
struct list_head list;
};
@ -731,6 +733,7 @@ static int gb_loopback_connection_init(struct gb_connection *connection)
struct gb_loopback *gb;
int retval;
char name[DEBUGFS_NAMELEN];
unsigned long flags;
gb = kzalloc(sizeof(*gb), GFP_KERNEL);
if (!gb)
@ -739,14 +742,13 @@ static int gb_loopback_connection_init(struct gb_connection *connection)
init_waitqueue_head(&gb->wq);
gb_loopback_reset_stats(gb);
mutex_lock(&gb_dev.mutex);
if (!gb_dev.count) {
/* Calculate maximum payload */
gb_dev.size_max = gb_operation_get_payload_size_max(connection);
if (gb_dev.size_max <=
sizeof(struct gb_loopback_transfer_request)) {
retval = -EINVAL;
goto out_sysfs;
goto out_kzalloc;
}
gb_dev.size_max -= sizeof(struct gb_loopback_transfer_request);
}
@ -783,10 +785,12 @@ static int gb_loopback_connection_init(struct gb_connection *connection)
goto out_kfifo1;
}
spin_lock_irqsave(&gb_dev.lock, flags);
gb_loopback_insert_id(gb);
gb_connection_latency_tag_enable(connection);
gb_dev.count++;
mutex_unlock(&gb_dev.mutex);
spin_unlock_irqrestore(&gb_dev.lock, flags);
gb_connection_latency_tag_enable(connection);
return 0;
out_kfifo1:
@ -798,7 +802,7 @@ static int gb_loopback_connection_init(struct gb_connection *connection)
out_sysfs:
debugfs_remove(gb->file);
connection->bundle->private = NULL;
mutex_unlock(&gb_dev.mutex);
out_kzalloc:
kfree(gb);
return retval;
@ -807,22 +811,24 @@ static int gb_loopback_connection_init(struct gb_connection *connection)
static void gb_loopback_connection_exit(struct gb_connection *connection)
{
struct gb_loopback *gb = connection->bundle->private;
unsigned long flags;
if (!IS_ERR_OR_NULL(gb->task))
kthread_stop(gb->task);
mutex_lock(&gb_dev.mutex);
connection->bundle->private = NULL;
kfifo_free(&gb->kfifo_lat);
kfifo_free(&gb->kfifo_ts);
gb_connection_latency_tag_disable(connection);
gb_dev.count--;
sysfs_remove_groups(&connection->bundle->dev.kobj,
loopback_groups);
debugfs_remove(gb->file);
spin_lock_irqsave(&gb_dev.lock, flags);
gb_dev.count--;
list_del(&gb->entry);
mutex_unlock(&gb_dev.mutex);
spin_unlock_irqrestore(&gb_dev.lock, flags);
kfree(gb);
}
@ -841,7 +847,7 @@ static int loopback_init(void)
int retval;
INIT_LIST_HEAD(&gb_dev.list);
mutex_init(&gb_dev.mutex);
spin_lock_init(&gb_dev.lock);
gb_dev.root = debugfs_create_dir("gb_loopback", NULL);
retval = gb_protocol_register(&loopback_protocol);