Table of Contents

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• Add new BUSY state functionality to the driver and the IOCTL protocol.

• In WPERF-116 we do not have to add special “transaction” business logic. For example we do not have to add any checks if we start counting if sampling is ongoing.

  • We will add business logic and tests as a separate functionality.

Required

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behaviour

1. Ultimatelly remove the call to WdfDeviceInitSetExclusive.

2. Create a persistent structure inside wperf-driver that capture driver’s “transition” current state, like if it is sampling, counting, if PMU resources are available or not. We want to capture:

   1. [bool flag] If driver is currently “counting” or “sampling” - this will set BUSY state to true.

   2. [IOCTL request no] Current IOCTL being processed - this is useful to determine in user space if we are actually counting/timeline or sampling or doing some other work.

3. How IOCTL will set BUSY state?

   1. Some IOCTL will set (and clear after IOCTL is finished) busy state during IOCTL handling only, e.g. PMU_CTL_RESET or IOCTL_PMU_CTL_QUERY_HW_CFG. This is because these “transactions” are pending during IOCTL handle and end after.

   2. Some IOCTLs will set BUSY state

   3. Not all IOCTLs may set bus state as some do not “set in motion” the driver.

4. Update to driver ↔︎ user-space protocol.

   1. User-space should handle properly BUSY state of the driver. E.g. warn that “continuing” IOCTL is ongoing.

      1. Please note this creates a “transaction” / “scenario” for WindowsPerf.

   2. We will send to user-space new set of flags:

      1. “current IOCTL” - which IOCTL is ongoing now.

      2. BUSY flag and at least info about which IOCTL is ongoing.

         1. If BUSY state is true: IOCTL field is valid with IOCTL being processed now.

      3. [to consider] “Invalid payload” - we may want to add to each IOCTL response with info if we managed to compose response payload.

         1. In scenarios when we send IOCTL_PMU_CTL_QUERY_HW_CFG during counting, the driver is busy but response payload would be valid as we can respond during counting.

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