MmUnmapLockedPages causing Bugcheck B8

[Shalini]

Hello Guys
My MmunMapLockedPages in IoCompletion routine is giving me Bugcheck B8 with
all the Args being NULL.
and moreever this happens only when the File system is NTFS.
Any ideas on how to proceed?
Has anyone come across these...

Sample code is as follows...

ASSERT((ewData->User)!=NULL);
ASSERT(Irp->MdlAddress!=NULL);
__try{
MmUnmapLockedPages(ewData->User, Irp->MdlAddress);
}
__except (EXCEPTION_EXECUTE_HANDLER)
{
KdPrint(("\nError in MmUnmapLockedPages"));
}

Regards
Shal

 

[Jonathan Morrison [MSFT]]

Can you attach the kernel debugger to the machine and send the callstack of
the thread that is bugchecking. A B8 bugcheck is a ATTEMPTED_SWITCH_FROM_DPC
(b8) bugcheck. The callstack should show the offending driver.

 

[Alexander Grigoriev]

This means the OP calls unmap for user space address from a DPC.