edac: core: remove completion-wait for complete with rcu_barrier

Module edac_core.ko uses call_rcu() callbacks in edac_device.c, edac_mc.c
and edac_pci.c.

They all use a wait_for_completion() scheme, but this scheme it not 100%
safe on multiple CPUs.  See the _rcu_barrier() implementation which
explains why extra precausion is needed.

The patch adds a comment about rcu_barrier() and as a precausion calls
rcu_barrier().  A maintainer needs to look at removing the
wait_for_completion code.

[dougthompson@xmission.com: remove the wait_for_completion code]
Signed-off-by Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 3 insertions, 10 deletions

diff --git a/drivers/edac/edac_device.c b/drivers/edac/edac_device.c
index b02a6a69a8f0..d5e13c94714f 100644
--- a/drivers/edac/edac_device.c
+++ b/drivers/edac/edac_device.c
@@ -356,7 +356,6 @@ static void complete_edac_device_list_del(struct rcu_head *head)
 
         edac_dev = container_of(head, struct edac_device_ctl_info, rcu);
         INIT_LIST_HEAD(&edac_dev->link);
-        complete(&edac_dev->removal_complete);
 }
 
 /*
@@ -369,10 +368,8 @@ static void del_edac_device_from_global_list(struct edac_device_ctl_info
                                                 *edac_device)
 {
         list_del_rcu(&edac_device->link);
-
-        init_completion(&edac_device->removal_complete);
         call_rcu(&edac_device->rcu, complete_edac_device_list_del);
-        wait_for_completion(&edac_device->removal_complete);
+        rcu_barrier();
 }
 
 /*
diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 335b7ebdb11c..b629c41756f0 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -418,16 +418,14 @@ static void complete_mc_list_del(struct rcu_head *head)
 
         mci = container_of(head, struct mem_ctl_info, rcu);
         INIT_LIST_HEAD(&mci->link);
-        complete(&mci->complete);
 }
 
 static void del_mc_from_global_list(struct mem_ctl_info *mci)
 {
         atomic_dec(&edac_handlers);
         list_del_rcu(&mci->link);
-        init_completion(&mci->complete);
         call_rcu(&mci->rcu, complete_mc_list_del);
-        wait_for_completion(&mci->complete);
+        rcu_barrier();
 }
 
 /**
diff --git a/drivers/edac/edac_pci.c b/drivers/edac/edac_pci.c
index 30b585b1d60b..efb5d5650783 100644
--- a/drivers/edac/edac_pci.c
+++ b/drivers/edac/edac_pci.c
@@ -174,7 +174,6 @@ static void complete_edac_pci_list_del(struct rcu_head *head)
 
         pci = container_of(head, struct edac_pci_ctl_info, rcu);
         INIT_LIST_HEAD(&pci->link);
-        complete(&pci->complete);
 }
 
 /*
@@ -185,9 +184,8 @@ static void complete_edac_pci_list_del(struct rcu_head *head)
 static void del_edac_pci_from_global_list(struct edac_pci_ctl_info *pci)
 {
         list_del_rcu(&pci->link);
-        init_completion(&pci->complete);
         call_rcu(&pci->rcu, complete_edac_pci_list_del);
-        wait_for_completion(&pci->complete);
+        rcu_barrier();
 }
 
 #if 0