Perf: keep events across hotplug

Keep event list alive across a CPU hotplug so that perf
can resume when the CPU comes back online. Bring a CPU
online when exiting a perf session so it can be cleaned
up properly.

Change-Id: Ie0e4a43f751beb77afdc84e9d52b21780f279d80
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>
diff --git a/arch/arm/mach-msm/perf_debug.c b/arch/arm/mach-msm/perf_debug.c
index 70c8c68..478848d 100644
--- a/arch/arm/mach-msm/perf_debug.c
+++ b/arch/arm/mach-msm/perf_debug.c
@@ -31,6 +31,7 @@
 	"10 Perf: Fix counts across power collapse\n"
 	"12 Perf: Make per-process counters configurable\n"
 	"13 msm: perf: Add L2 support for tracecounters\n"
+	"14 Perf: keep events across hotplug\n"
 ;
 
 static ssize_t desc_read(struct file *fp, char __user *buf,