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Subject[PATCH] usb: xhci: Replace tasklet with work
Date
Tasklets have long been deprecated as being too heavy on the system
by running in irq context - and this is not a performance critical
path. If a higher priority process wants to run, it must wait for
the tasklet to finish before doing so.

dbc_rx_push() will now run in process context and have further
concurrency - tasklets being serialized among themselves, but this
is done holding the port_lock, so it should be fine.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
drivers/usb/host/xhci-dbgcap.h | 2 +-
drivers/usb/host/xhci-dbgtty.c | 19 +++++++++++--------
2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h
index c70b78d504eb..aec66009af51 100644
--- a/drivers/usb/host/xhci-dbgcap.h
+++ b/drivers/usb/host/xhci-dbgcap.h
@@ -104,7 +104,7 @@ struct dbc_port {
struct list_head read_pool;
struct list_head read_queue;
unsigned int n_read;
- struct tasklet_struct push;
+ struct work_struct push;

struct list_head write_pool;
struct kfifo write_fifo;
diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index ae4e4ab638b5..50da77d92cf6 100644
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -108,7 +108,7 @@ dbc_read_complete(struct xhci_dbc *dbc, struct dbc_request *req)

spin_lock_irqsave(&port->port_lock, flags);
list_add_tail(&req->list_pool, &port->read_queue);
- tasklet_schedule(&port->push);
+ schedule_work(&port->push);
spin_unlock_irqrestore(&port->port_lock, flags);
}

@@ -272,7 +272,7 @@ static void dbc_tty_unthrottle(struct tty_struct *tty)
unsigned long flags;

spin_lock_irqsave(&port->port_lock, flags);
- tasklet_schedule(&port->push);
+ schedule_work(&port->push);
spin_unlock_irqrestore(&port->port_lock, flags);
}

@@ -288,15 +288,18 @@ static const struct tty_operations dbc_tty_ops = {
.unthrottle = dbc_tty_unthrottle,
};

-static void dbc_rx_push(struct tasklet_struct *t)
+static void dbc_rx_push(struct work_struct *work)
{
struct dbc_request *req;
struct tty_struct *tty;
unsigned long flags;
bool do_push = false;
bool disconnect = false;
- struct dbc_port *port = from_tasklet(port, t, push);
- struct list_head *queue = &port->read_queue;
+ struct dbc_port *port;
+ struct list_head *queue;
+
+ port = container_of(work, struct dbc_port, push);
+ queue = &port->read_queue;

spin_lock_irqsave(&port->port_lock, flags);
tty = port->port.tty;
@@ -349,7 +352,7 @@ static void dbc_rx_push(struct tasklet_struct *t)
if (!list_empty(queue) && tty) {
if (!tty_throttled(tty)) {
if (do_push)
- tasklet_schedule(&port->push);
+ schedule_work(&port->push);
else
pr_warn("ttyDBC0: RX not scheduled?\n");
}
@@ -382,7 +385,7 @@ xhci_dbc_tty_init_port(struct xhci_dbc *dbc, struct dbc_port *port)
{
tty_port_init(&port->port);
spin_lock_init(&port->port_lock);
- tasklet_setup(&port->push, dbc_rx_push);
+ INIT_WORK(&port->push, dbc_rx_push);
INIT_LIST_HEAD(&port->read_pool);
INIT_LIST_HEAD(&port->read_queue);
INIT_LIST_HEAD(&port->write_pool);
@@ -394,7 +397,7 @@ xhci_dbc_tty_init_port(struct xhci_dbc *dbc, struct dbc_port *port)
static void
xhci_dbc_tty_exit_port(struct dbc_port *port)
{
- tasklet_kill(&port->push);
+ cancel_work_sync(&port->push);
tty_port_destroy(&port->port);
}

--
2.26.2
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