Messages in this thread | | | Subject | Re: [PATCH] console close race fix resend | From | Robert Love <> | Date | 11 Dec 2001 01:05:18 -0500 |
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On Mon, 2001-12-10 at 22:16, Gordon Oliver wrote:
> and (c) appears to still have a race... You should extract > the value from the structure inside the lock, otherwise you > will still race with con_close (though perhaps a smaller race) > but since the call to acquire_console_sem() can sleep, the > vt handle you have may be stale.
Ehh, I don't think so. Here is the whole patched function:
static void con_flush_chars(struct tty_struct *tty) { struct vt_struct *vt = (struct vt_struct *)tty->driver_data; if (in_interrupt()) /* from flush_to_ldisc */ return; pm_access(pm_con); acquire_console_sem(); if (vt) set_cursor(vt->vc_num); release_console_sem(); }
When we check vt, it isn't stale. vt is a _pointer_ to the data so that first reference against it is guaranteed to grab the correct value. The only possible race is between the if and the set_cursor, but that isn't an issue because we acquired the console semaphore. There is no race here.
> > Please, for all that is righteous, apply. > > please fix it better first... > (unless I am mistaken).
Thus, unless I am mistaken, it is fine. Please, apply.
Robert Love
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