[PATCH 15/23] Drivers: hv: Use RCU to protect access of HK_TYPE_MANAGED_IRQ cpumask

[Waiman Long]

As HK_TYPE_MANAGED_IRQ cpumask is going to be changeable at run time,
use RCU to protect access to the cpumask. The memory allocation
alloc_cpumask_var() call is done before taking the rcu_read_lock()
as this call can be sleepable.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
 drivers/hv/channel_mgmt.c | 15 +++++++++------
 drivers/hv/vmbus_drv.c    |  7 +++++--
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 84eb0a6a0b54..44441dafed90 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -752,13 +752,16 @@ static void init_vp_index(struct vmbus_channel *channel)
 	u32 i, ncpu = num_online_cpus();
 	cpumask_var_t available_mask;
 	struct cpumask *allocated_mask;
-	const struct cpumask *hk_mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
+	const struct cpumask *hk_mask;
 	u32 target_cpu;
 	int numa_node;
+	bool alloc_ok;
 
-	if (!perf_chn ||
-	    !alloc_cpumask_var(&available_mask, GFP_KERNEL) ||
-	    cpumask_empty(hk_mask)) {
+	alloc_ok = alloc_cpumask_var(&available_mask, GFP_KERNEL);
+	guard(rcu)();
+	hk_mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
+
+	if (!perf_chn || !alloc_ok || cpumask_empty(hk_mask)) {
 		/*
 		 * If the channel is not a performance critical
 		 * channel, bind it to VMBUS_CONNECT_CPU.
@@ -770,7 +773,7 @@ static void init_vp_index(struct vmbus_channel *channel)
 		channel->target_cpu = VMBUS_CONNECT_CPU;
 		if (perf_chn)
 			hv_set_allocated_cpu(VMBUS_CONNECT_CPU);
-		return;
+		goto out_free;
 	}
 
 	for (i = 1; i <= ncpu + 1; i++) {
@@ -808,7 +811,7 @@ static void init_vp_index(struct vmbus_channel *channel)
 	}
 
 	channel->target_cpu = target_cpu;
-
+out_free:
 	free_cpumask_var(available_mask);
 }
 
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 3faa74e49a6b..60c7a5ac15c0 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1763,8 +1763,11 @@ int vmbus_channel_set_cpu(struct vmbus_channel *channel, u32 target_cpu)
 	if (target_cpu >= nr_cpumask_bits)
 		return -EINVAL;
 
-	if (!cpumask_test_cpu(target_cpu, housekeeping_cpumask(HK_TYPE_MANAGED_IRQ)))
-		return -EINVAL;
+	scoped_guard(rcu) {
+		if (!cpumask_test_cpu(target_cpu,
+				      housekeeping_cpumask(HK_TYPE_MANAGED_IRQ)))
+			return -EINVAL;
+	}
 
 	if (!cpu_online(target_cpu))
 		return -EINVAL;
-- 
2.53.0