Dear all： Could I get your comments for the updates? If I can get a reply, it will help me a lot . Thanks https://lkml.org/lkml/2020/12/28/19 ******************************* ----Original mail ----- 发件人: gaoyan (RD) 发送时间: 2020年12月28日 15:16 收件人: paulus@xxxxxxxxx; davem@xxxxxxxxxxxxx; kuba@xxxxxxxxxx 抄送: linux-ppp@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; gaoyan (RD) <gao.yanB@xxxxxxx> 主题: [PATCH] net: remove disc_data_lock in ppp line discipline In tty layer, it use tty->ldisc_sem to proect tty_ldisc_ops. So I think tty->ldisc_sem can also protect tty->disc_data; For examlpe, When cpu A is running ppp_synctty_ioctl that hold the tty->ldisc_sem, at the same time if cpu B calls ppp_synctty_close, it will wait until cpu A release tty->ldisc_sem. So I think it is unnecessary to have the disc_data_lock; cpu A cpu B tty_ioctl tty_reopen ->hold tty->ldisc_sem ->hold tty->ldisc_sem(write), failed ->ld->ops->ioctl ->wait... ->release tty->ldisc_sem ->wait...OK,hold tty->ldisc_sem ->tty_ldisc_reinit ->tty_ldisc_close ->ld->ops->close Signed-off-by: Gao Yan <gao.yanB@xxxxxxx> --- drivers/net/ppp/ppp_async.c | 11 ++--------- drivers/net/ppp/ppp_synctty.c | 12 ++---------- 2 files changed, 4 insertions(+), 19 deletions(-) diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c index 29a0917a8..20b50facd 100644 --- a/drivers/net/ppp/ppp_async.c +++ b/drivers/net/ppp/ppp_async.c @@ -127,17 +127,13 @@ static const struct ppp_channel_ops async_ops = { * FIXME: this is no longer true. The _close path for the ldisc is * now guaranteed to be sane. */ -static DEFINE_RWLOCK(disc_data_lock); static struct asyncppp *ap_get(struct tty_struct *tty) { - struct asyncppp *ap; + struct asyncppp *ap = tty->disc_data; - read_lock(&disc_data_lock); - ap = tty->disc_data; if (ap != NULL) refcount_inc(&ap->refcnt); - read_unlock(&disc_data_lock); return ap; } @@ -214,12 +210,9 @@ ppp_asynctty_open(struct tty_struct *tty) static void ppp_asynctty_close(struct tty_struct *tty) { - struct asyncppp *ap; + struct asyncppp *ap = tty->disc_data; - write_lock_irq(&disc_data_lock); - ap = tty->disc_data; tty->disc_data = NULL; - write_unlock_irq(&disc_data_lock); if (!ap) return; diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c index 0f338752c..53fb68e29 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -129,17 +129,12 @@ ppp_print_buffer (const char *name, const __u8 *buf, int count) * * FIXME: Fixed in tty_io nowadays. */ -static DEFINE_RWLOCK(disc_data_lock); - static struct syncppp *sp_get(struct tty_struct *tty) { - struct syncppp *ap; + struct syncppp *ap = tty->disc_data; - read_lock(&disc_data_lock); - ap = tty->disc_data; if (ap != NULL) refcount_inc(&ap->refcnt); - read_unlock(&disc_data_lock); return ap; } @@ -213,12 +208,9 @@ ppp_sync_open(struct tty_struct *tty) static void ppp_sync_close(struct tty_struct *tty) { - struct syncppp *ap; + struct syncppp *ap = tty->disc_data; - write_lock_irq(&disc_data_lock); - ap = tty->disc_data; tty->disc_data = NULL; - write_unlock_irq(&disc_data_lock); if (!ap) return; -- 2.17.1
