Date: Sun, 03 Jun 2012 23:42:43 +0900 (JST) From: Mitsuru IWASAKI <iwasaki@jp.FreeBSD.org> To: avg@FreeBSD.org Cc: attilio@FreeBSD.org, freebsd-acpi@FreeBSD.org, freebsd-arch@FreeBSD.org Subject: Re: cpu stopping Message-ID: <20120603.234243.28389486.iwasaki@jp.FreeBSD.org> In-Reply-To: <4FCB0FE5.4050607@FreeBSD.org> References: <20120603.002554.119853142.iwasaki@jp.FreeBSD.org> <CAJ-FndAfm4_XqFSwBqXK=cgWkE6YVrtkS5BbcH7zcRd-100xTw@mail.gmail.com> <4FCB0FE5.4050607@FreeBSD.org>
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Hi, thanks for comments.
> As the first thing I must admit that I haven't looked at the patch :-)
Never mind :) What I'm trying to do in the patches is just to unify
amd64/i386 independent part (acpi_wakeup.c) for the code maintenance,
so please let's commit it first, then start re-design the
cpususpend_handler().
> But really I don't see why we need to differentiate between stopped and
> suspended state as both of them ultimately mean exactly the same thing - CPUs
> are spinning on some condition (and they are in a well-defined place and state).
Yes, amd64/i386 cpususpend_handler() is very similar to cpustop_handler()
actually, some resume related procedures are added for suspend.
> My view of how this should work is:
> - there can be only one master CPU that controls all other (slave) CPUs
> - the master sets entry and exit hooks
Entry hook for suspending might be
----
ctx_fpusave(suspfpusave[cpu]);
wbinvd();
CPU_SET_ATOMIC(cpu, &stopped_cpus);
----
and for stopping is
----
/* Indicate that we are stopped */
CPU_SET_ATOMIC(cpu, &stopped_cpus);
----
Correct?
I think stopping hook can be replaced with suspending hook.
Exit hook for suspending is
----
pmap_init_pat();
load_cr3(susppcbs[cpu]->pcb_cr3);
initializecpu();
PCPU_SET(switchtime, 0);
PCPU_SET(switchticks, ticks);
[snip]
/* Resume MCA and local APIC */
mca_resume();
lapic_setup(0);
----
For stopping should be
----
if (cpu == 0 && cpustop_restartfunc != NULL) {
cpustop_restartfunc();
cpustop_restartfunc = NULL;
}
----
> - the master signals slaves to enter the stop state
> - the slaves execute the enter hook and start spinning on the release condition
> - the master does whatever it wants to do in this special system state
> - the master signals the slaves to resume
> - the slave exit the spin loop and execute the exit hook
I think it would be possible. However I personally think that
priority of x86/x86/mp_machdep.c is higher and more effective than
merging cpususpend/stop_handler().
Thanks
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