perf/hwpb: Invoke __perf_event_disable() if interrupts are already disabled

Hello K.Prasad,

This is a semi-automatic email about new static checker warnings.

The patch 500ad2d8b013: "perf/hwpb: Invoke __perf_event_disable() if interrupts are already disabled" from Aug 2, 2012, leads to the following Smatch complaint:

kernel/events/hw_breakpoint.c:449 modify_user_hw_breakpoint()

	 error: we previously assumed 'bp->ctx' could be null (see line 446)

kernel/events/hw_breakpoint.c
445 */
446 if (irqs_disabled() && bp->ctx && bp->ctx->task = current)

                                       ^^^^^^^

We add a new assumption that bp->ctx can be NULL in this patch.

447 __perf_event_disable(bp);
448 else

   449			perf_event_disable(bp);
                        ^^^^^^^^^^^^^^^^^^^^^^

But it is dereferenced unconditionally in perf_event_disable().

   450	
   451		bp->attr.bp_addr = attr->bp_addr;

regards,
dan carpenter