Re: [PATCH V5 06/14] powerpc/vas: Setup thread IRQ handler per VAS instance

On Fri, 2020-02-07 at 16:57 +1100, Michael Neuling wrote:

quoted

 /*
+ * Process CRBs that we receive on the fault window.
+ */
+irqreturn_t vas_fault_handler(int irq, void *data)
+{
+	struct vas_instance *vinst = data;
+	struct coprocessor_request_block buf, *crb;
+	struct vas_window *window;
+	void *fifo;
+
+	/*
+	 * VAS can interrupt with multiple page faults. So process all
+	 * valid CRBs within fault FIFO until reaches invalid CRB.
+	 * NX updates nx_fault_stamp in CRB and pastes in fault FIFO.
+	 * kernel retrives send window from parition send window ID
+	 * (pswid) in nx_fault_stamp. So pswid should be non-zero and
+	 * use this to check whether CRB is valid.
+	 * After reading CRB entry, it is reset with 0's in fault FIFO.
+	 *
+	 * In case kernel receives another interrupt with different page
+	 * fault and CRBs are processed by the previous handling, will be
+	 * returned from this function when it sees invalid CRB (means 0's).
+	 */
+	do {
+		mutex_lock(&vinst->mutex);

This isn't going to work.

From Documentation/locking/mutex-design.rst

    - Mutexes may not be used in hardware or software interrupt
      contexts such as tasklets and timers.

Initially used kernel thread per VAS instance and later using IRQ
thread. 

vas_fault_handler() is IRQ thread function, not IRQ handler. I thought
we can use mutex_lock() in thread function.

Mikey