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[PATCH] Fix race condition in hvc console. 

tty_schedule_flip() would schedule a thread that would call flush_to_ldisc().
If tty_buffer_request_room() gets called prior to that thread running --
which is likely in this loop in hvc_poll(), it would set the active flag
in the tty buffer and consequently flush_to_ldisc() would ignore it.

The result is that input on the hvc console is not processed.

This fix calls tty_flip_buffer_push (and flags the tty as
"low_latency").  The push to the ldisc thus happens synchronously.

Signed-off-by: Michal Ostrowski <mostrows@watson.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Michal Ostrowski 2006-02-18 09:29:59 -05:00 committed by Paul Mackerras
parent 4558f417f4
commit fb5c594c2a
1 changed files with 5 additions and 3 deletions
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8
drivers/char/hvc_console.c
View File

@ -335,6 +335,8 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
} /* else count == 0 */
tty->driver_data = hp;
tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */
hp->tty = tty;
/* Save for request_irq outside of spin_lock. */
irq = hp->irq;
@ -633,9 +635,6 @@ static int hvc_poll(struct hvc_struct *hp)
tty_insert_flip_char(tty, buf[i], 0);
}
if (count)
tty_schedule_flip(tty);
/*
* Account for the total amount read in one loop, and if above
* 64 bytes, we do a quick schedule loop to let the tty grok
@ -656,6 +655,9 @@ static int hvc_poll(struct hvc_struct *hp)
bail:
spin_unlock_irqrestore(&hp->lock, flags);
if (read_total)
tty_flip_buffer_push(tty);
return poll_mask;
}