Re: NvmExpressDxe async application crash with UDK debugger

[Arka Sharma <arka.sw1988@gmail.com>]

There is a mistake I had in my code. The NVMe command Packet is a
local variable to ReadSectors, whose address is being passed to
PassThru. So PassThru will return after pushing the command to async
submission queue  and create an AsyncRequest and insert it in
AsyncPassThruQueueand return. So the AsyncRequest->Packet is holding
an address of a stack variable of ReadSector. After getting return
from PassThru the ReadSector also return after that. This left the
address of Packet to be stale which is being access in
ProcessAsyncTaskList at
        //
        // Copy the Respose Queue entry for this command to the callers
        // response buffer.
        //
        CopyMem (
          AsyncRequest->Packet->NvmeCompletion,
          Cq,
          sizeof(EFI_NVM_EXPRESS_COMPLETION)
          );
In this case AsyncRequest->Packet is a stale address. I allocated
Packet structure using AllocateZeroPool in ReadSectors and run the
application multiple times and have not yet observed crash. Thanks for
your effort and apologize for my mistake.

Regards,
Arka

On Thu, Apr 13, 2017 at 11:16 AM, Wu, Hao A <hao.a.wu@intel.com> wrote:
> Hi Arka,
>
> I will help to look into this problem and will try to reproduce it first.
>
> Best Regards,
> Hao Wu
>
>
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Arka
>> Sharma
>> Sent: Wednesday, April 12, 2017 2:05 PM
>> To: Tian, Feng
>> Cc: edk2-devel@lists.01.org
>> Subject: Re: [edk2] NvmExpressDxe async application crash with UDK debugger
>>
>> Please find attached source. Also the variables to detect completion are
>> not volatile. I have checked in disassembly they are fetched from memory in
>> the completion loop.
>>
>> Regards,
>> Arka
>>
>> On 12 Apr 2017 10:37 a.m., "Tian, Feng" <feng.tian@intel.com> wrote:
>>
>> > Arka,
>> >
>> > Could you please share us your test code?
>> >
>> > Thanks
>> > Feng
>> >
>> > -----Original Message-----
>> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
>> > Arka Sharma
>> > Sent: Wednesday, April 12, 2017 12:59 PM
>> > To: edk2-devel@lists.01.org
>> > Subject: [edk2] NvmExpressDxe async application crash with UDK debugger
>> >
>> > Hi,
>> >
>> > I am testing async io in NvmExpressDxe. The target system is Asrock
>> > Z97 which I have connected to host with serial port where UDK debugger is
>> > running. So my application does following
>> >
>> > 1. CreateEvent
>> > 2. Call Passthru
>> > 3. CmdSent++;
>> > 4. Repeat 1-3 until not ready from driver 5. while (CmdRecd < CmdSent); 4.
>> > Close all the events.
>> >
>> > CmdRecvd is incremented inside EventCallback. I am allocating both CmdSent
>> > and CmdRecvd and passing the address of CmdRecvd in CreateEvent. With
>> this
>> > I face WinDbg exception quite often and it says "Target encountered an
>> > exception: Vector = 6, Error Code = 00000000".
>> > I can share the application code for more clarity. I am building with /Od
>> > and GenFw with --keepexceptiontable
>> >
>> > Regards,
>> > Arka
>> > _______________________________________________
>> > edk2-devel mailing list
>> > edk2-devel@lists.01.org
>> > https://lists.01.org/mailman/listinfo/edk2-devel
>> >
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