Subj : DOS EMM calls in a TSR
To   : ALL
From : Jcurtis
Date : Tue Jun 24 2025 20:27:48

By trial and error I discovered EMM calls enable interrupts. This can
cause havoc in a TSR where you need interrupts disabled. Finding these
bugs is not easy. My TSR enables interrupts part of the time, so I do
EMM calls there. Here's an example with comments.

void
next_irq (void)
{
    int x;

  next:
    x = next ();                        /* service IRQs with */
    enable ();                          /* interrupts enabled */

# ifndef noemm                          /* EMM call enables interrupts, do */
    emm_get_page_map (e1);              /* not do it before enable () above */
# endif

    if (x) {
        service_com_irqs (x);

    } else
        service_ticktock ();

# ifndef noemm
    emm_set_page_map (e1);
# endif

    disable ();
    if (x)
        mask_irq (NO, x);

    if (iq[iz])
        goto next;
}

 * SLMR 2.1a *

 * SLMR 2.1a * 

---
 þ Synchronet þ Vertrauen þ Home of Synchronet þ [vert/cvs/bbs].synchro.net

.