Messages in this thread Patch in this message | | | From | Gao Yan <> | Subject | [PATCH] net: remove unnecessary disc_data_lock in ppp line discipline | Date | Fri, 21 May 2021 15:57:26 +0800 |
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In tty layer, it use tty->ldisc_sem(using tty_ldisc_ref_wait and tty_ldisc_deref) 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 define additional 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@h3c.com> --- drivers/net/ppp/ppp_async.c | 11 ++--------- drivers/net/ppp/ppp_synctty.c | 11 ++--------- 2 files changed, 4 insertions(+), 18 deletions(-)
diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c index 8b41aa3fb..7bc4846f5 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 576b6a93b..812f309c5 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -129,17 +129,13 @@ 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 +209,9 @@ 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
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