Daniel Veillard wrote:
> On Thu, Jan 24, 2013 at 12:55:09PM -0700, Jim Fehlig wrote:
>
>> Jim Fehlig wrote:
>>
>>> xen-unstable commit XXXX makes changes wrt modifying and deregistering
>>> timeouts.
>>>
>>> First, timeout modify callbacks will only be invoked with an
>>> abs_t of {0,0}, i.e. make the timeout fire immediately. Prior to this
>>> commit, timeout modify callbacks were never invoked.
>>>
>>> Second, timeout deregister hooks will no longer be called.
>>>
>>> This patch makes changes in the libvirt libxl driver that should be
>>> compatible before and after commit XXXX.
>>>
>>> While at it, fix a potential overflow in the timeout register callback.
>>> ---
>>>
>>> 'commit XXXX' will be replaced with a proper commit id once committed
>>> to xen-unstable.
>>>
>>>
>> libxl patch as been committed to xen-unstable now, changeset 26469.
>> I've updated this patch accordingly.
>>
>> Regards,
>> Jim
>>
>>
>>
>
>
>> >From 451c84284fa1b4f311f2ceb052c8e9f25ffa0cf0 Mon Sep 17 00:00:00 2001
>> From: Jim Fehlig <jfehlig@xxxxxxxx>
>> Date: Mon, 21 Jan 2013 09:59:28 -0700
>> Subject: [PATCH 1/6] libxl: Fix handling of timeouts
>>
>> xen-unstable changeset 26469 makes changes wrt modifying and deregistering
>> timeouts.
>>
>> First, timeout modify callbacks will only be invoked with an
>> abs_t of {0,0}, i.e. make the timeout fire immediately. Prior to this
>> commit, timeout modify callbacks were never invoked.
>>
>> Second, timeout deregister hooks will no longer be called.
>>
>> This patch makes changes in the libvirt libxl driver that should be
>> compatible before and after changeset 26469.
>>
>> While at it, fix a potential overflow in the timeout register callback.
>> ---
>> src/libxl/libxl_driver.c | 39 ++++++++++++++++++++++++++++++---------
>> 1 file changed, 30 insertions(+), 9 deletions(-)
>>
>> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
>> index a8c4cae..77026fc 100644
>> --- a/src/libxl/libxl_driver.c
>> +++ b/src/libxl/libxl_driver.c
>> @@ -186,7 +186,13 @@ libxlTimerCallback(int timer ATTRIBUTE_UNUSED, void *timer_info)
>> {
>> struct libxlOSEventHookTimerInfo *info = timer_info;
>>
>> + /* libxl expects the event to be deregistered when calling
>> + libxl_osevent_occurred_timeout, but we dont want the event info
>> + destroyed. Disable the timeout and only remove it after returning
>> + from libxl. */
>> + virEventUpdateTimeout(info->id, -1);
>> libxl_osevent_occurred_timeout(info->priv->ctx, info->xl_priv);
>> + virEventRemoveTimeout(info->id);
>> }
>>
>> static void
>> @@ -202,6 +208,8 @@ libxlTimeoutRegisterEventHook(void *priv,
>> void *xl_priv)
>> {
>> struct timeval now;
>> + struct timeval res;
>> + static struct timeval zero;
>> struct libxlOSEventHookTimerInfo *timer_info;
>> int timeout, timer_id;
>>
>> @@ -211,8 +219,15 @@ libxlTimeoutRegisterEventHook(void *priv,
>> }
>>
>> gettimeofday(&now, NULL);
>> - timeout = (abs_t.tv_usec - now.tv_usec) / 1000;
>> - timeout += (abs_t.tv_sec - now.tv_sec) * 1000;
>> + timersub(&abs_t, &now, &res);
>> + /* Ensure timeout is not overflowed */
>> + if (timercmp(&res, &zero, <)) {
>> + timeout = 0;
>> + } else if (res.tv_sec > INT_MAX / 1000) {
>> + timeout = INT_MAX;
>> + } else {
>> + timeout = res.tv_sec * 1000 + (res.tv_usec + 999) / 1000;
>> + }
>> timer_id = virEventAddTimeout(timeout, libxlTimerCallback,
>> timer_info, libxlTimerInfoFree);
>> if (timer_id < 0) {
>> @@ -227,19 +242,25 @@ libxlTimeoutRegisterEventHook(void *priv,
>> return 0;
>> }
>>
>> +/*
>> + * Note: There are two changes wrt timeouts starting with xen-unstable
>> + * changeset 26469:
>> + *
>> + * 1. Timeout modify callbacks will only be invoked with an abs_t of {0,0},
>> + * i.e. make the timeout fire immediately. Prior to this commit, timeout
>> + * modify callbacks were never invoked.
>> + *
>> + * 2. Timeout deregister hooks will no longer be called.
>> + */
>> static int
>> libxlTimeoutModifyEventHook(void *priv ATTRIBUTE_UNUSED,
>> void **hndp,
>> - struct timeval abs_t)
>> + struct timeval abs_t ATTRIBUTE_UNUSED)
>> {
>> - struct timeval now;
>> - int timeout;
>> struct libxlOSEventHookTimerInfo *timer_info = *hndp;
>>
>> - gettimeofday(&now, NULL);
>> - timeout = (abs_t.tv_usec - now.tv_usec) / 1000;
>> - timeout += (abs_t.tv_sec - now.tv_sec) * 1000;
>> - virEventUpdateTimeout(timer_info->id, timeout);
>> + /* Make the timeout fire */
>> + virEventUpdateTimeout(timer_info->id, 0);
>> return 0;
>> }
>>
>>
>
> ACK, I assume you tested with the older libxl, right ?
>
Yes, but with limited success due to the issue described here
http://lists.xen.org/archives/html/xen-devel/2012-11/msg01016.html
With Ian Jackson's libxl fixes, I've been able to do several hundred
save/restore iterations. Without his libxl fixes, I'd be lucky to get
beyond 5 iterations.
http://lists.xen.org/archives/html/xen-devel/2013-01/msg01971.html
Those libxl fixes will be included in the xen 4.2 branch too, and will
be available in 4.2.2.
Thanks!
Jim
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