[RFC 1/6] ethdev: fix flow_ops_mutex for multi-process

[Stephen Hemminger <stephen@networkplumber.org>]

The flow_ops_mutex in rte_eth_dev_data is located in shared memory
that is accessed by both primary and secondary processes. However,
the mutex is initialized without PTHREAD_PROCESS_SHARED attribute,
which means synchronization between processes is undefined behavior.

POSIX mutexes are by default private to the process creating them.
When a mutex protects data structures in shared memory that are
accessed by multiple processes, pthread_mutexattr_setpshared() must
be called with PTHREAD_PROCESS_SHARED.

This bug has existed since the flow_ops_mutex was added and affects
any multi-process DPDK application using rte_flow APIs.

Bugzilla ID: 662
Fixes: 80d1a9aff7f6 ("ethdev: make flow API thread safe")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/ethdev/ethdev_driver.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/ethdev/ethdev_driver.c b/lib/ethdev/ethdev_driver.c
index 2ec665be0f..d12395efe0 100644
--- a/lib/ethdev/ethdev_driver.c
+++ b/lib/ethdev/ethdev_driver.c
@@ -89,6 +89,22 @@ eth_dev_set_dummy_fops(struct rte_eth_dev *eth_dev)
 	eth_dev->recycle_rx_descriptors_refill = rte_eth_recycle_rx_descriptors_refill_dummy;
 }
 
+/*
+ * Initialize mutex for process-shared access.
+ * The rte_eth_dev_data structure is in shared memory, so any mutex
+ * protecting it must use PTHREAD_PROCESS_SHARED.
+ */
+static void
+eth_dev_flow_ops_mutex_init(pthread_mutex_t *mutex)
+{
+	pthread_mutexattr_t attr;
+
+	pthread_mutexattr_init(&attr);
+	pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
+	pthread_mutex_init(mutex, &attr);
+	pthread_mutexattr_destroy(&attr);
+}
+
 RTE_EXPORT_INTERNAL_SYMBOL(rte_eth_dev_allocate)
 struct rte_eth_dev *
 rte_eth_dev_allocate(const char *name)
@@ -135,7 +151,7 @@ rte_eth_dev_allocate(const char *name)
 	eth_dev->data->port_id = port_id;
 	eth_dev->data->backer_port_id = RTE_MAX_ETHPORTS;
 	eth_dev->data->mtu = RTE_ETHER_MTU;
-	pthread_mutex_init(&eth_dev->data->flow_ops_mutex, NULL);
+	eth_dev_flow_ops_mutex_init(&eth_dev->data->flow_ops_mutex);
 	RTE_ASSERT(rte_eal_process_type() == RTE_PROC_PRIMARY);
 	eth_dev_shared_data->allocated_ports++;
 
-- 
2.51.0