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[PATCH] RDMA/ocrdma: Don't sleep in atomic notifier handler

 

 

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levinsasha928 at gmail

Apr 27, 2012, 10:40 PM

Post #1 of 2 (66 views)
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[PATCH] RDMA/ocrdma: Don't sleep in atomic notifier handler

Events sent to ocrdma_inet6addr_event() are sent from an atomic context, therefore
we can't try to lock a mutex within the notifier callback.

We could just switch the mutex to a spinlock since all it does it protect a list,
but I've went ahead and switched the list to use RCU instead. I couldn't fully test
it since I don't have IB hardware, so if it doesn't fully work for some reason let
me know and I'll switch it back to using a spinlock.

Signed-off-by: Sasha Levin <levinsasha928 [at] gmail>
---
drivers/infiniband/hw/ocrdma/ocrdma.h | 1 +
drivers/infiniband/hw/ocrdma/ocrdma_main.c | 38 ++++++++++++++++-----------
2 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/drivers/infiniband/hw/ocrdma/ocrdma.h b/drivers/infiniband/hw/ocrdma/ocrdma.h
index d7a44b8..85a69c9 100644
--- a/drivers/infiniband/hw/ocrdma/ocrdma.h
+++ b/drivers/infiniband/hw/ocrdma/ocrdma.h
@@ -168,6 +168,7 @@ struct ocrdma_dev {
struct be_dev_info nic_info;

struct list_head entry;
+ struct rcu_head rcu;
int id;
};

diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_main.c b/drivers/infiniband/hw/ocrdma/ocrdma_main.c
index cee201e..bc9009f 100644
--- a/drivers/infiniband/hw/ocrdma/ocrdma_main.c
+++ b/drivers/infiniband/hw/ocrdma/ocrdma_main.c
@@ -47,7 +47,7 @@ MODULE_AUTHOR("Emulex Corporation");
MODULE_LICENSE("GPL");

static LIST_HEAD(ocrdma_dev_list);
-static DEFINE_MUTEX(ocrdma_devlist_lock);
+static DEFINE_SPINLOCK(ocrdma_devlist_lock);
static DEFINE_IDR(ocrdma_dev_id);

static union ib_gid ocrdma_zero_sgid;
@@ -221,14 +221,14 @@ static int ocrdma_inet6addr_event(struct notifier_block *notifier,
is_vlan = true;
vid = vlan_dev_vlan_id(event_netdev);
}
- mutex_lock(&ocrdma_devlist_lock);
- list_for_each_entry(dev, &ocrdma_dev_list, entry) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(dev, &ocrdma_dev_list, entry) {
if (dev->nic_info.netdev == netdev) {
found = true;
break;
}
}
- mutex_unlock(&ocrdma_devlist_lock);
+ rcu_read_unlock();

if (!found)
return NOTIFY_DONE;
@@ -431,9 +431,9 @@ static struct ocrdma_dev *ocrdma_add(struct be_dev_info *dev_info)
if (status)
goto alloc_err;

- mutex_lock(&ocrdma_devlist_lock);
- list_add_tail(&dev->entry, &ocrdma_dev_list);
- mutex_unlock(&ocrdma_devlist_lock);
+ spin_lock(&ocrdma_devlist_lock);
+ list_add_tail_rcu(&dev->entry, &ocrdma_dev_list);
+ spin_lock(&ocrdma_devlist_lock);
return dev;

alloc_err:
@@ -448,16 +448,9 @@ idr_err:
return NULL;
}

-static void ocrdma_remove(struct ocrdma_dev *dev)
+static void ocrdma_remove_free(struct rcu_head *rcu)
{
- /* first unregister with stack to stop all the active traffic
- * of the registered clients.
- */
- ib_unregister_device(&dev->ibdev);
-
- mutex_lock(&ocrdma_devlist_lock);
- list_del(&dev->entry);
- mutex_unlock(&ocrdma_devlist_lock);
+ struct ocrdma_dev *dev = container_of(rcu, struct ocrdma_dev, rcu);

ocrdma_free_resources(dev);
ocrdma_cleanup_hw(dev);
@@ -467,6 +460,19 @@ static void ocrdma_remove(struct ocrdma_dev *dev)
ib_dealloc_device(&dev->ibdev);
}

+static void ocrdma_remove(struct ocrdma_dev *dev)
+{
+ /* first unregister with stack to stop all the active traffic
+ * of the registered clients.
+ */
+ ib_unregister_device(&dev->ibdev);
+
+ spin_lock(&ocrdma_devlist_lock);
+ list_del_rcu(&dev->entry);
+ spin_unlock(&ocrdma_devlist_lock);
+ call_rcu(&dev->rcu, ocrdma_remove_free);
+}
+
static int ocrdma_open(struct ocrdma_dev *dev)
{
struct ib_event port_event;
--
1.7.8.5

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roland at kernel

May 2, 2012, 3:46 PM

Post #2 of 2 (64 views)
Permalink
Re: [PATCH] RDMA/ocrdma: Don't sleep in atomic notifier handler [In reply to]

On Fri, Apr 27, 2012 at 10:40 PM, Sasha Levin <levinsasha928 [at] gmail> wrote:
> +       spin_lock(&ocrdma_devlist_lock);
> +       list_add_tail_rcu(&dev->entry, &ocrdma_dev_list);
> +       spin_lock(&ocrdma_devlist_lock);

Er, applied with this fixed to be spin_unlock at the end...
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