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| author | Mike Marciniszyn <mike.marciniszyn@intel.com> | 2015-11-02 12:13:25 -0500 |
|---|---|---|
| committer | Doug Ledford <dledford@redhat.com> | 2015-12-07 16:39:26 -0500 |
| commit | d144da8c6f51f48ec39d891ea9dff80169c45f3b (patch) | |
| tree | b2cc120f870989c2cb4cdd328d0cf7f8355eb012 | |
| parent | 57ab2512138205fe7836332fb4742441e53907ff (diff) | |
| download | linux-d144da8c6f51f48ec39d891ea9dff80169c45f3b.tar.bz2 | |
IB/core: use RCU for uverbs id lookup
The current implementation gets a spin_lock, and at any scale with
qib and hfi1 post send, the lock contention grows exponentially
with the number of QPs.
idr_find() is RCU compatibile, so read doesn't need the lock.
Change to use rcu_read_lock() and rcu_read_unlock() in
__idr_get_uobj().
kfree_rcu() is used to insure a grace period between the
idr removal and actual free.
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
| -rw-r--r-- | drivers/infiniband/core/uverbs_cmd.c | 12 | ||||
| -rw-r--r-- | include/rdma/ib_verbs.h | 1 |
2 files changed, 8 insertions, 5 deletions
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c index 4cb8e9d9966c..1c02deab068f 100644 --- a/drivers/infiniband/core/uverbs_cmd.c +++ b/drivers/infiniband/core/uverbs_cmd.c @@ -62,9 +62,11 @@ static struct uverbs_lock_class rule_lock_class = { .name = "RULE-uobj" }; * The ib_uobject locking scheme is as follows: * * - ib_uverbs_idr_lock protects the uverbs idrs themselves, so it - * needs to be held during all idr operations. When an object is + * needs to be held during all idr write operations. When an object is * looked up, a reference must be taken on the object's kref before - * dropping this lock. + * dropping this lock. For read operations, the rcu_read_lock() + * and rcu_write_lock() but similarly the kref reference is grabbed + * before the rcu_read_unlock(). * * - Each object also has an rwsem. This rwsem must be held for * reading while an operation that uses the object is performed. @@ -96,7 +98,7 @@ static void init_uobj(struct ib_uobject *uobj, u64 user_handle, static void release_uobj(struct kref *kref) { - kfree(container_of(kref, struct ib_uobject, ref)); + kfree_rcu(container_of(kref, struct ib_uobject, ref), rcu); } static void put_uobj(struct ib_uobject *uobj) @@ -145,7 +147,7 @@ static struct ib_uobject *__idr_get_uobj(struct idr *idr, int id, { struct ib_uobject *uobj; - spin_lock(&ib_uverbs_idr_lock); + rcu_read_lock(); uobj = idr_find(idr, id); if (uobj) { if (uobj->context == context) @@ -153,7 +155,7 @@ static struct ib_uobject *__idr_get_uobj(struct idr *idr, int id, else uobj = NULL; } - spin_unlock(&ib_uverbs_idr_lock); + rcu_read_unlock(); return uobj; } diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h index 9a68a19532ba..120da1d7f57e 100644 --- a/include/rdma/ib_verbs.h +++ b/include/rdma/ib_verbs.h @@ -1271,6 +1271,7 @@ struct ib_uobject { int id; /* index into kernel idr */ struct kref ref; struct rw_semaphore mutex; /* protects .live */ + struct rcu_head rcu; /* kfree_rcu() overhead */ int live; }; |