From 9f4e8a6c460bc3e64f4587e2942225d66e99d99b Mon Sep 17 00:00:00 2001
From: Imran Khan <kimran@codeaurora.org>
Date: Mon, 31 Jul 2017 14:37:18 +0530
Subject: [PATCH] Revert "perf: stop deadlock if attempt to bring cpu up fails"

This reverts 'commit 5f71e693df3a ("perf: stop deadlock if attempt
to bring cpu up fails")' as this change is not needed.

Change-Id: I17e6f7c1b648a5f2559eeea786efafc9be32a9e9
Signed-off-by: Imran Khan <kimran@codeaurora.org>
---
 drivers/perf/arm_pmu.c        |  1 +
 kernel/events/core.c          | 39 ++++++++++++++++++++++++++++++++++-
 kernel/events/hw_breakpoint.c |  2 ++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 63ec68e6ac2a..39400dda27c2 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -552,6 +552,7 @@ static void armpmu_init(struct arm_pmu *armpmu)
 		.stop		= armpmu_stop,
 		.read		= armpmu_read,
 		.filter_match	= armpmu_filter_match,
+		.events_across_hotplug = 1,
 	};
 }
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7fee87daac56..6cd152e99891 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1693,7 +1693,33 @@ static int __perf_remove_from_context(void *info)
 	return 0;
 }
 
-/*
+
+#ifdef CONFIG_SMP
+static void perf_retry_remove(struct perf_event *event,
+			      struct remove_event *rep)
+{
+	int up_ret;
+	/*
+	 * CPU was offline. Bring it online so we can
+	 * gracefully exit a perf context.
+	 */
+	up_ret = cpu_up(event->cpu);
+	if (!up_ret)
+		/* Try the remove call once again. */
+		cpu_function_call(event->cpu, __perf_remove_from_context,
+				  rep);
+	else
+		pr_err("Failed to bring up CPU: %d, ret: %d\n",
+		       event->cpu, up_ret);
+}
+#else
+static void perf_retry_remove(struct perf_event *event,
+			      struct remove_event *rep)
+{
+}
+#endif
+
+ /*
  * Remove the event from a task's (or a CPU's) list of events.
  *
  * CPU events are removed with a smp call. For task events we only
@@ -1728,6 +1754,9 @@ static void __ref perf_remove_from_context(struct perf_event *event,
 		 */
 		ret = cpu_function_call(event->cpu, __perf_remove_from_context,
 					&re);
+		if (ret == -ENXIO)
+			perf_retry_remove(event, &re);
+
 		return;
 	}
 
@@ -7109,6 +7138,8 @@ static struct pmu perf_swevent = {
 	.start		= perf_swevent_start,
 	.stop		= perf_swevent_stop,
 	.read		= perf_swevent_read,
+
+	.events_across_hotplug = 1,
 };
 
 #ifdef CONFIG_EVENT_TRACING
@@ -7230,6 +7261,8 @@ static struct pmu perf_tracepoint = {
 	.start		= perf_swevent_start,
 	.stop		= perf_swevent_stop,
 	.read		= perf_swevent_read,
+
+	.events_across_hotplug = 1,
 };
 
 static inline void perf_tp_register(void)
@@ -7517,6 +7550,8 @@ static struct pmu perf_cpu_clock = {
 	.start		= cpu_clock_event_start,
 	.stop		= cpu_clock_event_stop,
 	.read		= cpu_clock_event_read,
+
+	.events_across_hotplug = 1,
 };
 
 /*
@@ -7598,6 +7633,8 @@ static struct pmu perf_task_clock = {
 	.start		= task_clock_event_start,
 	.stop		= task_clock_event_stop,
 	.read		= task_clock_event_read,
+
+	.events_across_hotplug = 1,
 };
 
 static void perf_pmu_nop_void(struct pmu *pmu)
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 92ce5f4ccc26..7da5b674d16e 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -614,6 +614,8 @@ static struct pmu perf_breakpoint = {
 	.start		= hw_breakpoint_start,
 	.stop		= hw_breakpoint_stop,
 	.read		= hw_breakpoint_pmu_read,
+
+	.events_across_hotplug = 1,
 };
 
 int __init init_hw_breakpoint(void)