On Thursday 28 April 2005 03:24, Yu Dong-W4760C wrote:
> same bugs in the two files (uml-linux-2.4.26-3):
> arch/um/drivers/line.c
> down(&line->sem); ========================> may cause shedule in
> interrrupt
> in arch/um/drivers/stdio_console.c
> static void console_write(struct console *console, const char *string,
> unsigned len)
> {
> if(con_init_done)
> down(&line->sem); ========================> may cause shedule in
> interrrupt console_write_chan(&line->chan_list, string, len);
> if(con_init_done)
> up(&line->sem);
> }
>
> my fix is change
> [EMAIL PROTECTED] drivers]$ diff -Nru line.c line.c.old
> --- line.c 2005-04-28 09:22:29.000000000 +0800
> +++ line.c.old 2005-04-26 09:38:18.000000000 +0800
> @@ -134,9 +134,7 @@
> i = minor(tty->device) - tty->driver.minor_start;
> line = &lines[i];
>
> - if(!in_interrupt())
> - down(&line->sem);
> -
> + down(&line->sem);
> if(line->head != line->tail){
> local_irq_save(flags);
> ret += buffer_data(line, buf, len);
> @@ -159,8 +157,7 @@
> ret += buffer_data(line, buf + n, len);
> }
> out_up:
> - if(!in_interrupt())
> - up(&line->sem);
> + up(&line->sem);
>
> out_free:
> if(from_user)
>
>
> --- stdio_console.c 2005-04-26 14:41:05.000000000 +0800
> +++ stdio_console.c.bak 2005-04-26 14:33:30.000000000 +0800
> @@ -188,10 +188,10 @@
> {
> struct line *line = &vts[console->index];
>
> - if(con_init_done && !in_interrupt())
> + if(con_init_done)
> down(&line->sem);
> console_write_chan(&line->chan_list, string, len);
> - if(con_init_done && !in_interrupt())
> + if(con_init_done)
> up(&line->sem);
> }
>
> please help to confirm if it's correct?
1) The patch is reversed, and after noticing this it seems a bit more
meaningful.
2)But that's not the correct fix, because data corruption is as bad as
schedule in interrupt.
3) The correct fix (which I just sent in with the title "uml: redo console
locking" to this list) is to replace that semaphore with a spinlock.
--
Paolo Giarrusso, aka Blaisorblade
Skype user "PaoloGiarrusso"
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade
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