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authorMichal Ostrowski <mostrows@watson.ibm.com>2006-02-18 09:29:59 -0500
committerPaul Mackerras <paulus@samba.org>2006-02-23 19:36:40 -0500
commitfb5c594c2acc441f0d2d8f457484a0e0e9285db3 (patch)
tree0465b7b5fb518f21f6d4689e027f0f04bb3ebe35
parent4558f417f49595337b7e9cc3e92bc0856c588ac1 (diff)
[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>
-rw-r--r--drivers/char/hvc_console.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index 1994a92d4733..f65b2e14a485 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -335,6 +335,8 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
335 } /* else count == 0 */ 335 } /* else count == 0 */
336 336
337 tty->driver_data = hp; 337 tty->driver_data = hp;
338 tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */
339
338 hp->tty = tty; 340 hp->tty = tty;
339 /* Save for request_irq outside of spin_lock. */ 341 /* Save for request_irq outside of spin_lock. */
340 irq = hp->irq; 342 irq = hp->irq;
@@ -633,9 +635,6 @@ static int hvc_poll(struct hvc_struct *hp)
633 tty_insert_flip_char(tty, buf[i], 0); 635 tty_insert_flip_char(tty, buf[i], 0);
634 } 636 }
635 637
636 if (count)
637 tty_schedule_flip(tty);
638
639 /* 638 /*
640 * Account for the total amount read in one loop, and if above 639 * Account for the total amount read in one loop, and if above
641 * 64 bytes, we do a quick schedule loop to let the tty grok 640 * 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)
656 bail: 655 bail:
657 spin_unlock_irqrestore(&hp->lock, flags); 656 spin_unlock_irqrestore(&hp->lock, flags);
658 657
658 if (read_total)
659 tty_flip_buffer_push(tty);
660
659 return poll_mask; 661 return poll_mask;
660} 662}
661 663