From: Sumit Garg <sumit.garg@linaro.org>
To: kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org
Cc: gregkh@linuxfoundation.org, daniel.thompson@linaro.org,
jason.wessel@windriver.com, dianders@chromium.org,
jslaby@suse.com, linux@armlinux.org.uk,
linux-kernel@vger.kernel.org, Sumit Garg <sumit.garg@linaro.org>
Subject: [PATCH 7/7] serial: kgdb_nmi: Replace hrtimer with irq_work ping
Date: Mon, 22 Jun 2020 19:56:24 +0530 [thread overview]
Message-ID: <1592835984-28613-8-git-send-email-sumit.garg@linaro.org> (raw)
In-Reply-To: <1592835984-28613-1-git-send-email-sumit.garg@linaro.org>
From: Daniel Thompson <daniel.thompson@linaro.org>
Currently kgdb_nmi relies on a 100Hz timer to "defer" work from an NMI
handler. This is essentially doing the job that irq_work is designed to
do but in an odd and inefficient manner. Remove the timer code and
replace it with more appropriate irq_work related APIs.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
---
drivers/tty/serial/kgdb_nmi.c | 35 ++++++++++-------------------------
1 file changed, 10 insertions(+), 25 deletions(-)
diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c
index 2580f39..ad84eef 100644
--- a/drivers/tty/serial/kgdb_nmi.c
+++ b/drivers/tty/serial/kgdb_nmi.c
@@ -21,7 +21,7 @@
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/interrupt.h>
-#include <linux/hrtimer.h>
+#include <linux/irq_work.h>
#include <linux/tick.h>
#include <linux/kfifo.h>
#include <linux/kgdb.h>
@@ -127,7 +127,7 @@ static struct console kgdb_nmi_console = {
struct kgdb_nmi_tty_priv {
struct tty_port port;
- struct timer_list timer;
+ struct irq_work work;
STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;
};
@@ -141,13 +141,12 @@ static void kgdb_tty_recv(int ch)
if (!kgdb_nmi_port || ch < 0)
return;
/*
- * Can't use port->tty->driver_data as tty might be not there. Timer
- * will check for tty and will get the ref, but here we don't have to
- * do that, and actually, we can't: we're in NMI context, no locks are
- * possible.
+ * Can't use port->tty->driver_data as tty might be not there. Also, we
+ * can't even do that as we're in NMI context, no locks are possible.
*/
priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port);
kfifo_in(&priv->fifo, &c, 1);
+ irq_work_queue(&priv->work);
}
static int kgdb_nmi_poll_one_knock(void)
@@ -222,18 +221,12 @@ bool kgdb_nmi_poll_knock(void)
return true;
}
-/*
- * The tasklet is cheap, it does not cause wakeups when reschedules itself,
- * instead it waits for the next tick.
- */
-static void kgdb_nmi_tty_receiver(struct timer_list *t)
+static void kgdb_nmi_tty_receiver(struct irq_work *work)
{
- struct kgdb_nmi_tty_priv *priv = from_timer(priv, t, timer);
+ struct kgdb_nmi_tty_priv *priv =
+ container_of(work, struct kgdb_nmi_tty_priv, work);
char ch;
- priv->timer.expires = jiffies + (HZ/100);
- add_timer(&priv->timer);
-
if (likely(!atomic_read(&kgdb_nmi_num_readers) ||
!kfifo_len(&priv->fifo)))
return;
@@ -245,22 +238,13 @@ static void kgdb_nmi_tty_receiver(struct timer_list *t)
static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)
{
- struct kgdb_nmi_tty_priv *priv =
- container_of(port, struct kgdb_nmi_tty_priv, port);
-
kgdb_nmi_port = port;
- priv->timer.expires = jiffies + (HZ/100);
- add_timer(&priv->timer);
return 0;
}
static void kgdb_nmi_tty_shutdown(struct tty_port *port)
{
- struct kgdb_nmi_tty_priv *priv =
- container_of(port, struct kgdb_nmi_tty_priv, port);
-
- del_timer(&priv->timer);
kgdb_nmi_port = NULL;
}
@@ -279,7 +263,8 @@ static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty)
return -ENOMEM;
INIT_KFIFO(priv->fifo);
- timer_setup(&priv->timer, kgdb_nmi_tty_receiver, 0);
+ init_irq_work(&priv->work, kgdb_nmi_tty_receiver);
+ atomic_set(&priv->work.flags, IRQ_WORK_LAZY);
tty_port_init(&priv->port);
priv->port.ops = &kgdb_nmi_tty_port_ops;
tty->driver_data = priv;
--
2.7.4
prev parent reply other threads:[~2020-06-22 14:27 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 14:26 [PATCH 0/7] Enable support for kgdb NMI console feature Sumit Garg
2020-06-22 14:26 ` [PATCH 1/7] serial: kgdb_nmi: Allow NMI console to replace kgdb IO console Sumit Garg
2020-06-22 14:26 ` [PATCH 2/7] tty: serial: Add poll_get_irq() to the polling interface Sumit Garg
2020-06-22 15:56 ` Daniel Thompson
2020-06-23 7:48 ` Sumit Garg
2020-06-23 10:52 ` Daniel Thompson
2020-06-22 14:26 ` [PATCH 3/7] kgdb: Add request_nmi() to the io ops table for kgdboc Sumit Garg
2020-06-22 16:03 ` Daniel Thompson
2020-06-23 8:37 ` Sumit Garg
2020-06-23 10:59 ` Daniel Thompson
2020-06-26 19:44 ` Doug Anderson
2020-06-29 11:45 ` Daniel Thompson
2020-06-30 6:09 ` Sumit Garg
2020-06-22 14:26 ` [PATCH 4/7] serial: kgdb_nmi: Add support for interrupt based fallback Sumit Garg
2020-06-22 16:36 ` Daniel Thompson
2020-06-23 9:59 ` Sumit Garg
2020-06-22 14:26 ` [PATCH 5/7] serial: 8250: Implement poll_get_irq() interface Sumit Garg
2020-06-22 14:26 ` [PATCH 6/7] serial: amba-pl011: " Sumit Garg
2020-06-22 14:26 ` Sumit Garg [this message]
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