From: <li.hao40@zte.com.cn>
To: <jirislaby@kernel.org>
Cc: gregkh@linuxfoundation.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v3] tty: hvc: wakeup hvc console immediately when needed
Date: Mon, 15 Apr 2024 16:11:12 +0800 (CST) [thread overview]
Message-ID: <20240415161112945aW_GWw4iCWkUKN0lMSy-k@zte.com.cn> (raw)
From: Li Hao <li.hao40@zte.com.cn>
Cancel the do_wakeup flag in hvc_struct, and change it to immediately
wake up tty when hp->n_outbuf is 0 in hvc_push().
When we receive a key input character, the interrupt handling function
hvc_handle_interrupt() will be executed, and the echo thread
flush_to_ldisc() will be added to the queue.
If the user is currently using tcsetattr(), a hang may occur. tcsetattr()
enters kernel and waits for hp->n_outbuf to become 0 via
tty_wait_until_sent(). If the echo thread finishes executing before
reaching tty_wait_until_sent (for example, put_chars() takes too long),
it will cause while meeting the wakeup condition (hp->do_wakeup = 1),
tty_wait_until_sent() cannot be woken up (missed the tty_wakeup() of
this round's tty_poll). Unless the next key input character comes,
hvc_poll will be executed, and tty_wakeup() will be performed through
the do_wakeup flag.
Signed-off-by: Li Hao <li.hao40@zte.com.cn>
---
v2->v3:
According to:
https://lore.kernel.org/all/2024041531-caliber-overreach-2d4e@gregkh/
no change,place version information below the "---" line
v1->v2:
Some fixes according to:
https://lore.kernel.org/all/75dff5cd-7b0e-4039-9157-8bf10cf7ba29@kernel.org/
use tty_port_tty_wakeup() instead of tty_wakeup() to wake up tty
drivers/tty/hvc/hvc_console.c | 10 +++-------
drivers/tty/hvc/hvc_console.h | 1 -
2 files changed, 3 insertions(+), 8 deletions(-)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index cd1f657f7..cbd234847 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -480,7 +480,7 @@ static int hvc_push(struct hvc_struct *hp)
n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
if (n <= 0) {
if (n == 0 || n == -EAGAIN) {
- hp->do_wakeup = 1;
+ tty_port_tty_wakeup(&hp->port);
return 0;
}
/* throw away output on error; this happens when
@@ -491,7 +491,7 @@ static int hvc_push(struct hvc_struct *hp)
if (hp->n_outbuf > 0)
memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
else
- hp->do_wakeup = 1;
+ tty_port_tty_wakeup(&hp->port);
return n;
}
@@ -739,11 +739,7 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
poll_mask |= HVC_POLL_READ;
out:
- /* Wakeup write queue if necessary */
- if (hp->do_wakeup) {
- hp->do_wakeup = 0;
- tty_wakeup(tty);
- }
+ /* Wakeup in hvc_push */
bail:
spin_unlock_irqrestore(&hp->lock, flags);
diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h
index cf4c1af08..6622f71ba 100644
--- a/drivers/tty/hvc/hvc_console.h
+++ b/drivers/tty/hvc/hvc_console.h
@@ -36,7 +36,6 @@ struct hvc_struct {
struct tty_port port;
spinlock_t lock;
int index;
- int do_wakeup;
int outbuf_size;
int n_outbuf;
uint32_t vtermno;
--
2.25.1
reply other threads:[~2024-04-15 8:12 UTC|newest]
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