Commit 9ead190b authored by Roland Dreier's avatar Roland Dreier
Browse files

IB/uverbs: Don't serialize with ib_uverbs_idr_mutex

Currently, all userspace verbs operations that call into the kernel
are serialized by ib_uverbs_idr_mutex.  This can be a scalability
issue for some workloads, especially for devices driven by the ipath
driver, which needs to call into the kernel even for datapath

Fix this by adding reference counts to the userspace objects, and then
converting ib_uverbs_idr_mutex into a spinlock that only protects the
idrs long enough to take a reference on the object being looked up.
Because remove operations may fail, we have to do a slightly funky
two-step deletion, which is described in the comments at the top of

This also still leaves ib_uverbs_idr_lock as a single lock that is
possibly subject to contention.  However, the lock hold time will only
be a single idr operation, so multiple threads should still be able to
make progress, even if ib_uverbs_idr_lock is being ping-ponged.

Surprisingly, these changes even shrink the object code:

add/remove: 23/5 grow/shrink: 4/21 up/down: 633/-693 (-60)
Signed-off-by: default avatarRoland Dreier <>
parent c93b6fba
......@@ -132,7 +132,7 @@ struct ib_ucq_object {
u32 async_events_reported;
extern struct mutex ib_uverbs_idr_mutex;
extern spinlock_t ib_uverbs_idr_lock;
extern struct idr ib_uverbs_pd_idr;
extern struct idr ib_uverbs_mr_idr;
extern struct idr ib_uverbs_mw_idr;
......@@ -141,6 +141,8 @@ extern struct idr ib_uverbs_cq_idr;
extern struct idr ib_uverbs_qp_idr;
extern struct idr ib_uverbs_srq_idr;
void idr_remove_uobj(struct idr *idp, struct ib_uobject *uobj);
struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
int is_async, int *fd);
void ib_uverbs_release_event_file(struct kref *ref);
This diff is collapsed.
......@@ -66,7 +66,7 @@ enum {
static struct class *uverbs_class;
......@@ -183,21 +183,21 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
if (!context)
return 0;
list_for_each_entry_safe(uobj, tmp, &context->ah_list, list) {
struct ib_ah *ah = idr_find(&ib_uverbs_ah_idr, uobj->id);
idr_remove(&ib_uverbs_ah_idr, uobj->id);
struct ib_ah *ah = uobj->object;
idr_remove_uobj(&ib_uverbs_ah_idr, uobj);
list_for_each_entry_safe(uobj, tmp, &context->qp_list, list) {
struct ib_qp *qp = idr_find(&ib_uverbs_qp_idr, uobj->id);
struct ib_qp *qp = uobj->object;
struct ib_uqp_object *uqp =
container_of(uobj, struct ib_uqp_object, uevent.uobject);
idr_remove(&ib_uverbs_qp_idr, uobj->id);
idr_remove_uobj(&ib_uverbs_qp_idr, uobj);
ib_uverbs_detach_umcast(qp, uqp);
......@@ -206,11 +206,12 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
list_for_each_entry_safe(uobj, tmp, &context->cq_list, list) {
struct ib_cq *cq = idr_find(&ib_uverbs_cq_idr, uobj->id);
struct ib_cq *cq = uobj->object;
struct ib_uverbs_event_file *ev_file = cq->cq_context;
struct ib_ucq_object *ucq =
container_of(uobj, struct ib_ucq_object, uobject);
idr_remove(&ib_uverbs_cq_idr, uobj->id);
idr_remove_uobj(&ib_uverbs_cq_idr, uobj);
ib_uverbs_release_ucq(file, ev_file, ucq);
......@@ -218,10 +219,11 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
list_for_each_entry_safe(uobj, tmp, &context->srq_list, list) {
struct ib_srq *srq = idr_find(&ib_uverbs_srq_idr, uobj->id);
struct ib_srq *srq = uobj->object;
struct ib_uevent_object *uevent =
container_of(uobj, struct ib_uevent_object, uobject);
idr_remove(&ib_uverbs_srq_idr, uobj->id);
idr_remove_uobj(&ib_uverbs_srq_idr, uobj);
ib_uverbs_release_uevent(file, uevent);
......@@ -231,11 +233,11 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
/* XXX Free MWs */
list_for_each_entry_safe(uobj, tmp, &context->mr_list, list) {
struct ib_mr *mr = idr_find(&ib_uverbs_mr_idr, uobj->id);
struct ib_mr *mr = uobj->object;
struct ib_device *mrdev = mr->device;
struct ib_umem_object *memobj;
idr_remove(&ib_uverbs_mr_idr, uobj->id);
idr_remove_uobj(&ib_uverbs_mr_idr, uobj);
memobj = container_of(uobj, struct ib_umem_object, uobject);
......@@ -246,15 +248,14 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
list_for_each_entry_safe(uobj, tmp, &context->pd_list, list) {
struct ib_pd *pd = idr_find(&ib_uverbs_pd_idr, uobj->id);
idr_remove(&ib_uverbs_pd_idr, uobj->id);
struct ib_pd *pd = uobj->object;
idr_remove_uobj(&ib_uverbs_pd_idr, uobj);
return context->device->dealloc_ucontext(context);
......@@ -697,8 +697,12 @@ struct ib_ucontext {
struct ib_uobject {
u64 user_handle; /* handle given to us by userspace */
struct ib_ucontext *context; /* associated user context */
void *object; /* containing object */
struct list_head list; /* link to context's list */
u32 id; /* index into kernel idr */
struct kref ref;
struct rw_semaphore mutex; /* protects .live */
int live;
struct ib_umem {
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment