Re: Closing events and releasing resources in notify function

[Andrew Fish <afish@apple.com>]

> On Mar 24, 2017, at 12:07 AM, Arka Sharma <arka.sw1988@gmail.com> wrote:
> 
> Thanks Andrew for your reply. In this case I am creating the event
> with CreateEvent() and not with CreateEventEx(). I am attempting to
> free the Context inside the notify function which will be called after
> Event is signaled, and Context is only accessed before CreateEvent()
> and inside the NotifyRoutine(). So the change you are suggesting is
> inside the notify function I should call CloseEvent() first before
> freeing Context right ?
> 

Yes as your event can get signaled until you close it in the general case. 

Thanks,

Andrew Fish

> On Fri, Mar 24, 2017 at 12:07 PM, Andrew Fish <afish@apple.com> wrote:
>> 
>>> On Mar 23, 2017, at 11:22 PM, Arka Sharma <arka.sw1988@gmail.com> wrote:
>>> 
>>> Hi,
>>> 
>>> Is it ok to close the event and release the resource allocated to be
>>> sent as context inside the notify function. May be something like this
>>> 
>>> VOID
>>> EFIAPI
>>> NotifyRoutine (
>>>      EFI_EVENT Event,
>>>      VOID  *Context
>>> )
>>> {
>>>  //
>>>  // Perform intended task
>>>  //
>>>  FreePool (Context);
>>>  gBS->CloseEvent (Event);
>> 
>> You should close the event before you free the context, or you will have a race. You need to make sure there is no way for EFI to signal the event before you free the context.
>> 
>> This all assumes you don't have other code doing crazy stuff with the Context or Event. It would  be a different answer for CreateEventEx()
>> 
>> Thanks,
>> 
>> Andrew Fish
>> 
>>> }
>>> 
>>> In the above example Context was allocated before creating the event
>>> and passed as a parameter to CreateEvent().
>>> 
>>> Regards,
>>> Arka
>>> _______________________________________________
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>>> edk2-devel@lists.01.org
>>> https://lists.01.org/mailman/listinfo/edk2-devel
>>