| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Sun, 20 Jun 2010 20:48:54 +0200
From: "Henrik Rydberg" <rydberg@...omail.se>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
Jiri Kosina <jkosina@...e.cz>,
Mika Kuoppala <mika.kuoppala@...ia.com>,
Benjamin Tissoires <tissoire@...a.fr>,
Rafi Rubin <rafi@...s.upenn.edu>,
Henrik Rydberg <rydberg@...omail.se>
Subject: [PATCH] input: evdev: Use multi-reader buffer to save space (rev5)
Preparing for larger buffer needs, convert the current per-client
circular buffer to a single buffer with multiple clients. Ideally, there
should be a mechanism where clients wait during buffer collision only.
Meanwhile, let clients take the dev->event_lock, which is already held
during buffer writes.
Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
---
Hi Dmitry,
This is revision 5 of the evdev multi-reader buffer patch, fixing the
grab/ungrab bug mentioned in an earlier post.
Thanks,
Henrik
drivers/input/evdev.c | 65 ++++++++++++++++++++++++++++++++++---------------
1 files changed, 45 insertions(+), 20 deletions(-)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 2ee6c7a..da0fe3f 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -33,13 +33,13 @@ struct evdev {
spinlock_t client_lock; /* protects client_list */
struct mutex mutex;
struct device dev;
+ int head;
+ struct input_event buffer[EVDEV_BUFFER_SIZE];
};
struct evdev_client {
- struct input_event buffer[EVDEV_BUFFER_SIZE];
int head;
int tail;
- spinlock_t buffer_lock; /* protects access to buffer, head and tail */
struct fasync_struct *fasync;
struct evdev *evdev;
struct list_head node;
@@ -48,18 +48,13 @@ struct evdev_client {
static struct evdev *evdev_table[EVDEV_MINORS];
static DEFINE_MUTEX(evdev_table_mutex);
-static void evdev_pass_event(struct evdev_client *client,
- struct input_event *event)
+static inline void evdev_sync_event(struct evdev_client *client,
+ struct evdev *evdev, int type)
{
- /*
- * Interrupts are disabled, just acquire the lock
- */
- spin_lock(&client->buffer_lock);
- client->buffer[client->head++] = *event;
- client->head &= EVDEV_BUFFER_SIZE - 1;
- spin_unlock(&client->buffer_lock);
-
- if (event->type == EV_SYN)
+ /* sync the reader such that it never becomes empty */
+ if (client->tail != evdev->head)
+ client->head = evdev->head;
+ if (type == EV_SYN)
kill_fasync(&client->fasync, SIGIO, POLL_IN);
}
@@ -78,14 +73,18 @@ static void evdev_event(struct input_handle *handle,
event.code = code;
event.value = value;
+ /* dev->event_lock held */
+ evdev->buffer[evdev->head] = event;
+ evdev->head = (evdev->head + 1) & (EVDEV_BUFFER_SIZE - 1);
+
rcu_read_lock();
client = rcu_dereference(evdev->grab);
if (client)
- evdev_pass_event(client, &event);
+ evdev_sync_event(client, evdev, type);
else
list_for_each_entry_rcu(client, &evdev->client_list, node)
- evdev_pass_event(client, &event);
+ evdev_sync_event(client, evdev, type);
rcu_read_unlock();
@@ -149,11 +148,29 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
{
+ struct input_dev *dev = evdev->handle.dev;
+ int head, tail;
+
if (evdev->grab != client)
return -EINVAL;
+ spin_lock_irq(&dev->event_lock);
+
+ head = client->head;
+ tail = client->tail;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(client, &evdev->client_list, node) {
+ client->head = head;
+ client->tail = tail;
+ }
+ rcu_read_unlock();
+
rcu_assign_pointer(evdev->grab, NULL);
synchronize_rcu();
+
+ spin_unlock_irq(&dev->event_lock);
+
input_release_device(&evdev->handle);
return 0;
@@ -162,6 +179,7 @@ static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
static void evdev_attach_client(struct evdev *evdev,
struct evdev_client *client)
{
+ client->head = client->tail = evdev->head;
spin_lock(&evdev->client_lock);
list_add_tail_rcu(&client->node, &evdev->client_list);
spin_unlock(&evdev->client_lock);
@@ -269,7 +287,6 @@ static int evdev_open(struct inode *inode, struct file *file)
goto err_put_evdev;
}
- spin_lock_init(&client->buffer_lock);
client->evdev = evdev;
evdev_attach_client(evdev, client);
@@ -325,19 +342,27 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer,
}
static int evdev_fetch_next_event(struct evdev_client *client,
+ struct evdev *evdev,
struct input_event *event)
{
+ struct input_dev *dev = evdev->handle.dev;
int have_event;
- spin_lock_irq(&client->buffer_lock);
+ /*
+ * FIXME: taking event_lock protects against reentrant fops
+ * reads and provides sufficient buffer locking. However,
+ * clients should not block writes, and having multiple clients
+ * waiting for each other is suboptimal.
+ */
+ spin_lock_irq(&dev->event_lock);
have_event = client->head != client->tail;
if (have_event) {
- *event = client->buffer[client->tail++];
+ *event = evdev->buffer[client->tail++];
client->tail &= EVDEV_BUFFER_SIZE - 1;
}
- spin_unlock_irq(&client->buffer_lock);
+ spin_unlock_irq(&dev->event_lock);
return have_event;
}
@@ -366,7 +391,7 @@ static ssize_t evdev_read(struct file *file, char __user *buffer,
return -ENODEV;
while (retval + input_event_size() <= count &&
- evdev_fetch_next_event(client, &event)) {
+ evdev_fetch_next_event(client, evdev, &event)) {
if (input_event_to_user(buffer + retval, &event))
return -EFAULT;
--
1.6.3.3
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists