bnx2x: Revising locking scheme for MAC configuration

On very rare occasions, repeated load/unload stress test in the presence of
our storage driver (bnx2i/bnx2fc) causes a kernel panic in bnx2x code
(NULL pointer dereference). Stack traces indicate the issue happens during MAC
configuration; thorough code review showed that indeed several races exist
in which one thread can iterate over the list of configured MACs while another
deletes entries from the same list.

This patch adds a varient on the single-writer/Multiple-reader lock mechanism -
It utilizes an already exsiting bottom-half lock, using it so that Whenever
a writer is unable to continue due to the existence of another writer/reader,
it pends its request for future deliverance.
The writer / last readers will check for the existence of such requests and
perform them instead of the original initiator.
This prevents the writer from having to sleep while waiting for the lock
to be accessible, which might cause deadlocks given the locks already
held by the writer.

Another result of this patch is that setting of Rx Mode is now made in
sleepable context - Setting of Rx Mode is made under a bottom-half lock, which
was always nontrivial for the bnx2x driver, as the HW/FW configuration requires
wait for completions.
Since sleep was impossible (due to the sleepless-context), various mechanisms
were utilized to prevent the calling thread from sleep, but the truth was that
when the caller thread (i.e, the one calling ndo_set_rx_mode()) returned, the
Rx mode was still not set in HW/FW.

bnx2x_set_rx_mode() will now overtly schedule for the Rx changes to be
configured by the sp_rtnl_task which hold the RTNL lock and is sleepable
context.

Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.h b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.h
index 798dfe996733..533a3abd8c82 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.h
@@ -285,6 +285,12 @@ struct bnx2x_vlan_mac_obj {
 	 * entries.
 	 */
 	struct list_head		head;
+	/* Implement a simple reader/writer lock on the head list.
+	 * all these fields should only be accessed under the exe_queue lock
+	 */
+	u8		head_reader; /* Num. of readers accessing head list */
+	bool		head_exe_request; /* Pending execution request. */
+	unsigned long	saved_ramrod_flags; /* Ramrods of pending execution */
 
 	/* TODO: Add it's initialization in the init functions */
 	struct bnx2x_exe_queue_obj	exe_queue;
@@ -1302,8 +1308,16 @@ void bnx2x_init_vlan_mac_obj(struct bnx2x *bp,
 			     struct bnx2x_credit_pool_obj *macs_pool,
 			     struct bnx2x_credit_pool_obj *vlans_pool);
 
+int bnx2x_vlan_mac_h_read_lock(struct bnx2x *bp,
+					struct bnx2x_vlan_mac_obj *o);
+void bnx2x_vlan_mac_h_read_unlock(struct bnx2x *bp,
+				  struct bnx2x_vlan_mac_obj *o);
+int bnx2x_vlan_mac_h_write_lock(struct bnx2x *bp,
+				struct bnx2x_vlan_mac_obj *o);
+void bnx2x_vlan_mac_h_write_unlock(struct bnx2x *bp,
+					  struct bnx2x_vlan_mac_obj *o);
 int bnx2x_config_vlan_mac(struct bnx2x *bp,
-			  struct bnx2x_vlan_mac_ramrod_params *p);
+			   struct bnx2x_vlan_mac_ramrod_params *p);
 
 int bnx2x_vlan_mac_move(struct bnx2x *bp,
 			struct bnx2x_vlan_mac_ramrod_params *p,