2005-03-14 09:34:43

by moreau francis

Subject: [TTY] overrun notify issue during 5 minutes after booting

I noticed that TTY is not able to notify overrun issue
in "n_tty_receive_overrun". Actually it's because of
"time_before" macro which tests "tty->overrun_time"
(equals to 0) against "jiffies - HZ" (something very
big
after booting).
I guess a simple way to solve it, is to initialize
"tty->overrun_time" to "jiffies". But it won't work if
an overrun appear after a very long while....

Thanks

Francis






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2005-03-14 09:52:09

by Andrew Morton

Subject: Re: [TTY] overrun notify issue during 5 minutes after booting

moreau francis <[email protected]> wrote:
>
> I noticed that TTY is not able to notify overrun issue
> in "n_tty_receive_overrun". Actually it's because of
> "time_before" macro which tests "tty->overrun_time"
> (equals to 0) against "jiffies - HZ" (something very
> big
> after booting).
> I guess a simple way to solve it, is to initialize
> "tty->overrun_time" to "jiffies". But it won't work if
> an overrun appear after a very long while....

How does this look?


--- 25/drivers/char/tty_io.c~tty-overrun-time-fix 2005-03-14 01:45:43.000000000 -0800
+++ 25-akpm/drivers/char/tty_io.c 2005-03-14 01:46:02.000000000 -0800
@@ -2632,6 +2632,7 @@ static void initialize_tty_struct(struct
tty->magic = TTY_MAGIC;
tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
tty->pgrp = -1;
+ tty->overrun_time = jiffies;
tty->flip.char_buf_ptr = tty->flip.char_buf;
tty->flip.flag_buf_ptr = tty->flip.flag_buf;
INIT_WORK(&tty->flip.work, flush_to_ldisc, tty);
diff -puN drivers/char/n_tty.c~tty-overrun-time-fix drivers/char/n_tty.c
--- 25/drivers/char/n_tty.c~tty-overrun-time-fix 2005-03-14 01:49:25.000000000 -0800
+++ 25-akpm/drivers/char/n_tty.c 2005-03-14 01:50:10.000000000 -0800
@@ -606,9 +606,11 @@ static inline void n_tty_receive_overrun
char buf[64];

tty->num_overrun++;
- if (time_before(tty->overrun_time, jiffies - HZ)) {
- printk(KERN_WARNING "%s: %d input overrun(s)\n", tty_name(tty, buf),
- tty->num_overrun);
+ if (time_before(tty->overrun_time, jiffies - HZ) ||
+ time_after(tty->overrun_time, jiffies)) {
+ printk(KERN_WARNING "%s: %d input overrun(s)\n",
+ tty_name(tty, buf),
+ tty->num_overrun);
tty->overrun_time = jiffies;
tty->num_overrun = 0;
}
_

2005-03-14 14:17:58

by moreau francis

Subject: Re: [TTY] overrun notify issue during 5 minutes after booting

--- Andrew Morton <[email protected]> wrote:
> moreau francis <[email protected]> wrote:
>
> How does this look?
>

It works well though I haven't tested the second
correction. But it looks good...
By the way, is it safe in "n_tty_receive_overrun" to
call
"printk" ? because the former can be called from IT
context...

Francis






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2005-03-15 05:14:51

by Andrew Morton

Subject: Re: [TTY] overrun notify issue during 5 minutes after booting

moreau francis <[email protected]> wrote:
>
> By the way, is it safe in "n_tty_receive_overrun" to
> call
> "printk" ? because the former can be called from IT
> context...

yup. printk() is safe from all contexts except NMI.