[IA64] perfmon.c: cleanup system-wide context when closed from another cpu

- fix pfm_stop() and pfm_flush_pmds() to correctly cleanup
  in case of a system-wide context which is closed while running
  from another processor. This was leading to an assertion failure
  in pfm_loads_regs() for the next user of the PMU on the monitored
  CPU.
signed-off-by: stephane eranian <eranian@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/perfmon.c

@@ -3985,7 +3985,10 @@ pfm_stop(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
 	state     = ctx->ctx_state;
 	is_system = ctx->ctx_fl_system;
 
-	if (state != PFM_CTX_LOADED && state != PFM_CTX_MASKED) return -EINVAL;
+	/*
+	 * context must be attached to issue the stop command (includes LOADED,MASKED,ZOMBIE)
+	 */
+	if (state == PFM_CTX_UNLOADED) return -EINVAL;
 
 	/*
  	 * In system wide and when the context is loaded, access can only happen
@@ -6312,15 +6315,15 @@ pfm_flush_pmds(struct task_struct *task, pfm_context_t *ctx)
 	 */
 	is_self = ctx->ctx_task == task ? 1 : 0;
 
-#ifdef CONFIG_SMP
-	if (task == current) {
-#else
 	/*
-	 * in UP, the state can still be in the registers
+	 * can access PMU is task is the owner of the PMU state on the current CPU
+	 * or if we are running on the CPU bound to the context in system-wide mode
+	 * (that is not necessarily the task the context is attached to in this mode).
+	 * In system-wide we always have can_access_pmu true because a task running on an
+	 * invalid processor is flagged earlier in the call stack (see pfm_stop).
 	 */
-	if (task == current || GET_PMU_OWNER() == task) {
-#endif
-		can_access_pmu = 1;
+	can_access_pmu = (GET_PMU_OWNER() == task) || (ctx->ctx_fl_system && ctx->ctx_cpu == smp_processor_id());
+	if (can_access_pmu) {
 		/*
 		 * Mark the PMU as not owned
 		 * This will cause the interrupt handler to do nothing in case an overflow
@@ -6330,6 +6333,7 @@ pfm_flush_pmds(struct task_struct *task, pfm_context_t *ctx)
 		 * on.
 		 */
 		SET_PMU_OWNER(NULL, NULL);
+		DPRINT(("releasing ownership\n"));
 
 		/*
 		 * read current overflow status: