[RFC 3/6] net/atlantic: fix mbox_mutex for multi-process

[Stephen Hemminger <stephen@networkplumber.org>]

The Atlantic driver supports secondary processes, as shown by the
explicit check in eth_atl_dev_init(). The mbox_mutex in aq_hw_s
is located in dev_private which is in shared memory accessible
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.

Bugzilla ID: 662
Fixes: e9924638f5c9 ("net/atlantic: add FW mailbox guard mutex")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 drivers/net/atlantic/atl_ethdev.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/atlantic/atl_ethdev.c b/drivers/net/atlantic/atl_ethdev.c
index 2925dc2478..7282f9b691 100644
--- a/drivers/net/atlantic/atl_ethdev.c
+++ b/drivers/net/atlantic/atl_ethdev.c
@@ -3,6 +3,7 @@
  */
 
 #include <rte_string_fns.h>
+#include <pthread.h>
 #include <ethdev_pci.h>
 #include <rte_alarm.h>
 
@@ -355,6 +356,17 @@ atl_disable_intr(struct aq_hw_s *hw)
 	hw_atl_itr_irq_msk_clearlsw_set(hw, 0xffffffff);
 }
 
+static void
+atl_init_mutex(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);
+}
+
 static int
 eth_atl_dev_init(struct rte_eth_dev *eth_dev)
 {
@@ -405,7 +417,7 @@ eth_atl_dev_init(struct rte_eth_dev *eth_dev)
 
 	hw->aq_nic_cfg = &adapter->hw_cfg;
 
-	pthread_mutex_init(&hw->mbox_mutex, NULL);
+	atl_init_mutex(&hw->mbox_mutex);
 
 	/* disable interrupt */
 	atl_disable_intr(hw);
-- 
2.51.0