question powermac_smp_start_cpu return values vs. cpu_mp_unleash use of them (SMP context)

The following is based on head -r343670 .


( from /usr/src/sys/powerpc/powermac/platform_powermac.c )

static int
powermac_smp_start_cpu(platform_t plat, struct pcpu *pc)
{
#ifdef SMP
. . .
        while (!pc->pc_awake && timeout--)
                DELAY(100);

        return ((pc->pc_awake) ? 0 : EBUSY);
#else
. . .
#endif
}

So EBUSY above indicates pc->pc_awake==0 on return.
0 indicates pc->pc_awake!=0 .

But:
( from /usr/src/sys/powerpc/powerpc/mp_machdep.c )

static void
cpu_mp_unleash(void *dummy)
{
. . .
                        ret = platform_smp_start_cpu(pc);
                        if (ret == 0) {
                                timeout = 2000; /* wait 2sec for the AP */
                                while (!pc->pc_awake && --timeout > 0)
                                        DELAY(1000);
                        }
. . .
}

So cpu_mp_unleash only waits for pc->pc_awake!=0 if it it receives
a status value indicating that pc->pc_pc_awake was already not zero.
EBUSY results in no waiting in the cpu_mp_unleash code above despite
pc->pc_awake having been zero at the return.

How things match up for powermac seems odd to me. Is something wrong
here?

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

_______________________________________________
[email protected] mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-ppc
To unsubscribe, send any mail to "[email protected]"