From: Li Hao <li.ha...@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.ha...@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-4039-9157-8bf10cf7b...@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
