edac: core: remove completion-wait for complete with rcu_barrier
Jesper Dangaard Brouer [Wed, 23 Sep 2009 22:57:29 +0000 (15:57 -0700)]
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>

drivers/edac/edac_device.c
drivers/edac/edac_mc.c
drivers/edac/edac_pci.c

index b02a6a6..d5e13c9 100644 (file)
@@ -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();
 }
 
 /*
index 335b7eb..b629c41 100644 (file)
@@ -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();
 }
 
 /**
index 30b585b..efb5d56 100644 (file)
@@ -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