On 09/13/2018 07:15 AM, Wang Yechao wrote:
> user run "firewalld-cmd --reload"
> nwfilterStateReload called in main thread
> step 1. virRWLockWrite(&updateLock)
> step 2. virNWFilterLoadAllConfigs
> step 3. virRWLockUnlock(&updateLock);
>
> lauch a vm: qemuDomainCreateXML runs in other thread
> step 1. virRWLockRead(&updateLock);
> step 2. qemuProcessStart
> step 3. qemuProcessWaitForMonitor
> step 4. ...
> step 5 virRWLockUnlock(&updateLock);
>
> if nwfilterStateReload called in the middle of step 1 and step 5 of
> qemuDomainCreateXML, it can't get the updateLock and then block the
> event_loop,
> so event_loop can't handle the qemu-monitor messages, cause deadlock
>
> move nwfilterStateReload into thread to fix this problem.
>
> Signed-off-by: Wang Yechao <wang.yechao...@zte.com.cn>
> Reviewed-by: Wang Yi <wang.y...@zte.com.cn>
> ---
> src/nwfilter/nwfilter_driver.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
Couple of "administrative" comments - since you were a new contributor
to libvir-list - you just needed to be a bit more patient w/r/t getting
your patches on this list, as described here:
https://libvirt.org/hacking.html
"If everything went well, your patch should show up on the libvir-list
archives in a matter of minutes; if you still can't find it on there
after an hour or so, you should double-check your setup. Note that your
very first post to the mailing list will be subject to moderation, and
it's not uncommon for that to take around a day.
"
OK so that hopefully helps explain why there were many v1's posted
Then when you repost a few days later with something that's changed, you
need to change to using v2. In the postings on Sept 11 it seems you've
change the R-By email address. That's important enough to note...
Then when you posted as v2, it probably should have been v3 and a note
added why you changed from VIR_ERROR to VIR_WARN
For each of these addition versions after the "---" (above):
1. Add a pointer to the previous posting from the archives
2. Briefly describe the differences in the changes
So, after all that... This seemed really familiar... and it was:
See:
https://www.redhat.com/archives/libvir-list/2017-October/msg01351.html
and follow-ups:
https://www.redhat.com/archives/libvir-list/2017-December/msg00198.html
https://www.redhat.com/archives/libvir-list/2017-December/msg00227.html
However, that followup was essentially dropped. So this code once again
resurrects the same questions that I had back then.
Not that I don't think this should be done in some form, the question
becomes how much "care" needs to be taken to ensure we don't have
multiple threads running.
John
BTW: Whether you were aware of Nikolay's patch or not, I think some
attribution could be made even though it was the same solution.
> diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c
> index 1ee5162..ab85072 100644
> --- a/src/nwfilter/nwfilter_driver.c
> +++ b/src/nwfilter/nwfilter_driver.c
> @@ -80,18 +80,26 @@ static void nwfilterDriverUnlock(void)
> }
>
> #if HAVE_FIREWALLD
> +static void nwfilterReloadThread(void *opaque ATTRIBUTE_UNUSED)
> +{
> + nwfilterStateReload();
> +}
>
> static DBusHandlerResult
> nwfilterFirewalldDBusFilter(DBusConnection *connection ATTRIBUTE_UNUSED,
> DBusMessage *message,
> void *user_data ATTRIBUTE_UNUSED)
> {
> + virThread thread;
> +
> if (dbus_message_is_signal(message, DBUS_INTERFACE_DBUS,
> "NameOwnerChanged") ||
> dbus_message_is_signal(message, "org.fedoraproject.FirewallD1",
> "Reloaded")) {
> VIR_DEBUG("Reload in nwfilter_driver because of firewalld.");
> - nwfilterStateReload();
> +
> + if (virThreadCreate(&thread, false, nwfilterReloadThread, NULL) < 0)
> + VIR_WARN("create nwfilterReloadThread failed.");
> }
>
> return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
>
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