[libvirt] [PATCH] Drop dependency on pm-is-supported

[Cole Robinson]

On 03/28/2014 04:07 PM, Eric Blake wrote:
> On 03/28/2014 10:32 AM, Cédric Bosdonnat wrote:
>> From: Cédric Bosdonnat <cedric.bosdonnat at free.fr>
>>
>> pm-is-supported is the only thing needed in pm-utils, better get rid of
>> it since systemd is heavily used for libvirt.
>> ---
>>  src/util/virnodesuspend.c | 34 ++++++++++++++++++++--------------
>>  1 file changed, 20 insertions(+), 14 deletions(-)
> 
> You also need to modify libvirt.spec.in to drop the dependency.
> 
>>
>>  
>> +    if (virFileReadAll("/sys/power/state", 1024, &buf) < 0)
>> +        goto cleanup;
>> +
>> +    states = virStringSplit(buf, " ", 0);
>> +
>> +    canSuspend = (virStringArrayHasString(states, "mem") ||
>> +                  virStringArrayHasString(states, "standby"));
>> +    canHibernate = virStringArrayHasString(states, "disk");
> 
> pm-is-supported checks a bit more than what your replacement checks.
> 
> For suspend, it declares yes if any of these succeed:
> 	grep -q mem /sys/power/state
> 	[ -c /dev/pmu ] && pm-pmu --check
> 	grep -q standby /sys/power/state
> 
> For hibernate, it requires that BOTH of these succeed:
> 	[ -f /sys/power/disk ]
> 	grep -q disk /sys/power/state
> 
> For hybrid, it requires that all three succeed:
> 	[ -f /sys/power/disk ] && \
> 	grep -q disk /sys/power/state && \
> 	grep -q suspend /sys/power/disk
> 
> as well as having fallback code to fake a hybrid sleep by joining the
> other two states.
> 
> 
>> +
>>      switch (target) {
>>      case VIR_NODE_SUSPEND_TARGET_MEM:
>> -        cmd = virCommandNewArgList("pm-is-supported", "--suspend", NULL);
>> +        *supported = canSuspend;
>>          break;
>>      case VIR_NODE_SUSPEND_TARGET_DISK:
>> -        cmd = virCommandNewArgList("pm-is-supported", "--hibernate", NULL);
>> +        *supported = canHibernate;
>>          break;
>>      case VIR_NODE_SUSPEND_TARGET_HYBRID:
>> -        cmd = virCommandNewArgList("pm-is-supported", "--suspend-hybrid", NULL);
>> +        *supported = canSuspend && canHibernate;
> 
> I'm not sure if your simpler checks will cause us to declare an action
> unsupported on systems where it was previously declared supported by
> pm-is-supported.  I think the idea makes sense, but I'd like a second
> opinion that we aren't hurting ourselves by doing fewer checks than what
> we are replacing.

FWIW there's a fedora bug about dropping the libvirt dep:

https://bugzilla.redhat.com/show_bug.cgi?id=919390

And this:

https://www.redhat.com/archives/libvir-list/2013-August/msg00212.html

Which claims there's a logind replacement API. Since we aim to build on RHEL5
(where logind/systemd isn't available), maybe we should preserve this old
implementation and add a new one using the new APIs? Sufficiently new distros
just pass the needed configure flag in their build system.

- Cole