[PATCH v2 3/3] tty: hvc: hvc_write() fix break condition
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2018-09-09 05:39:43
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Subsystem:
hypervisor virtual console driver, the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
Commit 550ddadcc758 ("tty: hvc: hvc_write() may sleep") broke the
termination condition in case the driver stops accepting characters.
This can result in unnecessary polling of the busy driver.
Restore it by testing the hvc_push return code.
Tested-by: Matteo Croce <redacted>
Tested-by: Jason Gunthorpe <redacted>
Tested-by: Leon Romanovsky <redacted>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
drivers/tty/hvc/hvc_console.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index bacf9b73ec98..27284a2dcd2b 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c@@ -522,6 +522,8 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count return -EIO; while (count > 0) { + int ret = 0; + spin_lock_irqsave(&hp->lock, flags); rsize = hp->outbuf_size - hp->n_outbuf;
@@ -537,10 +539,13 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count } if (hp->n_outbuf > 0) - hvc_push(hp); + ret = hvc_push(hp); spin_unlock_irqrestore(&hp->lock, flags); + if (!ret) + break; + if (count) { if (hp->n_outbuf > 0) hvc_flush(hp);
--
2.18.0