Re: [PATCH] WorkStruct: Fix S390 driver workstruct usage

From: Al Viro
Date: Fri Dec 08 2006 - 13:46:50 EST


On Fri, Dec 08, 2006 at 02:59:40PM +0000, David Howells wrote:

> diff --git a/drivers/s390/char/ctrlchar.c b/drivers/s390/char/ctrlchar.c
> index 49e9628..9fcfe3a 100644
> --- a/drivers/s390/char/ctrlchar.c
> +++ b/drivers/s390/char/ctrlchar.c
> @@ -15,15 +15,16 @@ #include <linux/ctype.h>
> #include "ctrlchar.h"
>
> #ifdef CONFIG_MAGIC_SYSRQ
> +static struct tty_struct *ctrlchar_sysrq_tty;
> static int ctrlchar_sysrq_key;
>
> static void
> -ctrlchar_handle_sysrq(void *tty)
> +ctrlchar_handle_sysrq(struct work_struct *unused)
> {
> - handle_sysrq(ctrlchar_sysrq_key, (struct tty_struct *) tty);
> + handle_sysrq(ctrlchar_sysrq_key, ctrlchar_sysrq_tty);
> }
>
> -static DECLARE_WORK(ctrlchar_work, ctrlchar_handle_sysrq, NULL);
> +static DECLARE_WORK(ctrlchar_work, ctrlchar_handle_sysrq);
> #endif
>
>
> @@ -52,8 +53,8 @@ ctrlchar_handle(const unsigned char *buf
> #ifdef CONFIG_MAGIC_SYSRQ
> /* racy */
> if (len == 3 && buf[1] == '-') {
> + ctrlchar_sysrq_tty = tty;
> ctrlchar_sysrq_key = buf[2];
> - ctrlchar_work.data = tty;
> schedule_work(&ctrlchar_work);
> return CTRLCHAR_SYSRQ;
> }

I don't think it's a real fix.

a) what protects tty from disappearing?
b) why the hell do we need that schedule_work() at all? handle_sysrq() is
supposed to be safe to use from irq handler; when needed it does arrange for
delayed execution itself.

So how about we simply call handle_sysrq() there and be done with that?
Martin?
-
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