Andrew,
Your suggested code makes sense to me, I will give it a try. Besides that
sample code snippet, I don't think the spec isn't really explicit; but does
imply that the entire group is signaled, regardless of whether the event itself
is of type EVT_NOTIFY_SIGNAL.
-- Justin
-----Original Message-----
From: Andrew Fish [mailto:af...@apple.com]
Sent: Friday, May 30, 2014 2:19 PM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] Signalling an event group
On May 30, 2014, at 11:51 AM, Andrew Fish wrote:
>
> On May 30, 2014, at 11:00 AM, justin_johns...@dell.com wrote:
>
>> Hello all,
>> I'm working with the DXE core event services and am not sure that the code
>> in MdeModulePkg agrees with the UEFI spec.
>> The situation is this: in several modules I have created an event using the
>> CreateEventEx() method, with an EventGroup GUID. Later, I want to signal the
>> event group, but the module which does the signaling does not have any work
>> to do in response to the event. It would seem that I can signal the event by
>> doing as indicated in the UEFI spec:
>> gBS->CreateEventEx (
>> 0,
>> 0,
>> NULL,
>> NULL,
>> &gMyEventGroupGuid,
>> &Event);
>> gBS->SignalEvent(Event);
>>
>> However, this does not work with EDKII. I see in Event.c :
>> if ((Event->Type & EVT_NOTIFY_SIGNAL) != 0) {
>> if (Event->ExFlag) {
>> //
>> // The CreateEventEx() style requires all members of the Event Group
>> // to be signaled.
>> //
>> CoreReleaseEventLock ();
>> CoreNotifySignalList (&Event->EventGroup);
>> CoreAcquireEventLock ();
>>
>> Which seems to indicate that the event group is only signaled if the event
>> being signaled is of type EVT_NOTIFY_SIGNAL. In order to get my event group
>> signaled, I must create an event with a dummy callback and give it type
>> EVT_NOTIFY_SIGNAL, even though I do not have any work to do in response to
>> the event.
>>
>> Is this an error in MdeModulePkg's implementation? Or is the spec incomplete?
>>
Justin,
I think the logic in the DXE Core should look like this:
if (Event->SignalCount == 0x00000000) {
Event->SignalCount++;
if (Event->ExFlag) {
//
// The CreateEventEx() style requires all members of the Event Group
// to be signaled.
//
CoreReleaseEventLock ();
CoreNotifySignalList (&Event->EventGroup);
CoreAcquireEventLock ();
} else if ((Event->Type & EVT_NOTIFY_SIGNAL) != 0) {
//
// If signalling type is a notify function, queue it
//
CoreNotifyEvent (Event);
}
}
So always walk the List for an Ex event, but only notify the event if it is the
right type. And the check should be in CoreNotifySignalList()
VOID
CoreNotifySignalList (
IN EFI_GUID *EventGroup
)
{
LIST_ENTRY *Link;
LIST_ENTRY *Head;
IEVENT *Event;
CoreAcquireEventLock ();
Head = &gEventSignalQueue;
for (Link = Head->ForwardLink; Link != Head; Link = Link->ForwardLink) {
Event = CR (Link, IEVENT, SignalLink, EVENT_SIGNATURE);
if (CompareGuid (&Event->EventGroup, EventGroup)) {
if ((Event->Type & EVT_NOTIFY_SIGNAL) != 0) {
CoreNotifyEvent (Event);
}
}
}
CoreReleaseEventLock ();
}
Man, this code has been busted for a long time.... This bug predates the edk2!
The edk2 UefiLib even has a Dummy event and tries to hide the need for it from
the caller....
https://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg/Library/UefiLib/UefiNotTiano.c
/**
An empty function to pass error checking of CreateEventEx ().
This empty function ensures that EVT_NOTIFY_SIGNAL_ALL is error
checked correctly since it is now mapped into CreateEventEx() in UEFI 2.0.
@param Event Event whose notification function is being invoked.
@param Context The pointer to the notification function's context,
which is implementation-dependent.
**/
VOID
EFIAPI
InternalEmptyFunction (
IN EFI_EVENT Event,
IN VOID *Context
)
{
return;
}
EFI_STATUS
EFIAPI
EfiCreateEventReadyToBootEx (
IN EFI_TPL NotifyTpl,
IN EFI_EVENT_NOTIFY NotifyFunction, OPTIONAL
IN VOID *NotifyContext, OPTIONAL
OUT EFI_EVENT *ReadyToBootEvent
)
{
EFI_STATUS Status;
EFI_EVENT_NOTIFY WorkerNotifyFunction;
ASSERT (ReadyToBootEvent != NULL);
if (gST->Hdr.Revision < EFI_2_00_SYSTEM_TABLE_REVISION) {
DEBUG ((EFI_D_ERROR, "EFI1.1 can't support ReadyToBootEvent!"));
ASSERT (FALSE);
return EFI_UNSUPPORTED;
} else {
//
// For UEFI 2.0 and the future use an Event Group
//
if (NotifyFunction == NULL) {
//
// CreateEventEx will check NotifyFunction is NULL or not and return error.
// Use dummy routine for the case NotifyFunction is NULL.
//
WorkerNotifyFunction = InternalEmptyFunction;
} else {
WorkerNotifyFunction = NotifyFunction;
}
Status = gBS->CreateEventEx (
EVT_NOTIFY_SIGNAL,
NotifyTpl,
WorkerNotifyFunction,
NotifyContext,
&gEfiEventReadyToBootGuid,
ReadyToBootEvent
);
}
return Status;
}
Thanks,
Andrew Fish
>> Thanks.
>>
>> --
>> Justin Johnson
>> Platform Software Engineer
>> Dell, Inc.
>>
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>
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