[RFC PATCH v2 2/7] dmaengine: rebalance DMA channels when CPU hotplug happens

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From: Jiang Liu <jiang.liu@xxxxxxxxxx>

Rebalance DMA channels when CPU hotplug happens to correctly update
DMA channel reference count.

Signed-off-by: Jiang Liu <liuj97@xxxxxxxxx>
---
 drivers/dma/dmaengine.c |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 58bc45c..d3b1c48 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -49,6 +49,7 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/cpu.h>
 #include <linux/device.h>
 #include <linux/dmaengine.h>
 #include <linux/hardirq.h>
@@ -1003,8 +1004,29 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
 }
 EXPORT_SYMBOL_GPL(dma_run_dependencies);
 
+static int __cpuinit
+hotcpu_rebalance(struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+	switch (action) {
+	case CPU_ONLINE:
+	case CPU_POST_DEAD:
+		mutex_lock(&dma_list_mutex);
+		dma_channel_rebalance();
+		mutex_unlock(&dma_list_mutex);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block __refdata dma_cpu_notifier = {
+	.notifier_call = hotcpu_rebalance,
+};
+
+
 static int __init dma_bus_init(void)
 {
+	register_hotcpu_notifier(&dma_cpu_notifier);
 	return class_register(&dma_devclass);
 }
 arch_initcall(dma_bus_init);
-- 
1.7.9.5

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