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Subject[PATCH v2 13/16] tty: Use non-atomic state to signal flip buffer flush pending
Date
Atomic bit ops are no longer required to indicate a flip buffer
flush is pending, as the flush_mutex is sufficient barrier.

Remove the unnecessary port .iflags field and localize flip buffer
state to struct tty_bufhead.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/tty_buffer.c | 7 ++++---
include/linux/tty.h | 3 +--
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 39cae61..fb042b9 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -189,11 +189,11 @@ void tty_buffer_flush(struct tty_struct *tty)
struct tty_port *port = tty->port;
struct tty_bufhead *buf = &port->buf;

- set_bit(TTYP_FLUSHPENDING, &port->iflags);
+ buf->flushpending = 1;

mutex_lock(&buf->flush_mutex);
__tty_buffer_flush(port);
- clear_bit(TTYP_FLUSHPENDING, &port->iflags);
+ buf->flushpending = 0;
mutex_unlock(&buf->flush_mutex);
}

@@ -426,7 +426,7 @@ static void flush_to_ldisc(struct work_struct *work)
int count;

/* Ldisc or user is trying to flush the buffers. */
- if (test_bit(TTYP_FLUSHPENDING, &port->iflags))
+ if (buf->flushpending)
break;

count = head->commit - head->read;
@@ -505,6 +505,7 @@ void tty_buffer_init(struct tty_port *port)
buf->tail = &buf->sentinel;
init_llist_head(&buf->free);
atomic_set(&buf->memory_used, 0);
+ buf->flushpending = 0;
INIT_WORK(&buf->work, flush_to_ldisc);
}

diff --git a/include/linux/tty.h b/include/linux/tty.h
index b8e8adf..991575f 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -68,6 +68,7 @@ struct tty_bufhead {
struct tty_buffer *head; /* Queue head */
struct work_struct work;
struct mutex flush_mutex;
+ unsigned int flushpending:1;
struct tty_buffer sentinel;
struct llist_head free; /* Free queue head */
atomic_t memory_used; /* In-use buffers excluding free list */
@@ -212,8 +213,6 @@ struct tty_port {
wait_queue_head_t close_wait; /* Close waiters */
wait_queue_head_t delta_msr_wait; /* Modem status change */
unsigned long flags; /* TTY flags ASY_*/
- unsigned long iflags; /* TTYP_ internal flags */
-#define TTYP_FLUSHPENDING 2 /* Queued buffer flush pending */
unsigned char console:1, /* port is a console */
low_latency:1; /* direct buffer flush */
struct mutex mutex; /* Locking */
--
1.8.1.2


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