This patch presents some concept about lockless scheme. It's only
intended to open discussion and still misses some crucial parts.
Every ib_uobject has a usecnt atomic variable. Single rwsem in
ib_uverbs_file (protect destruction of device from execution of
commands).
For every command execution:
a. Check if device is available (as of today, with srcu)
b. Take down_read(&file->close_sem)
c. <User is now protected from closing the process and ib-dev
destruction>
d. When an object is used -> use uverbs_lock_object function
implemented in this patch.
i .If the object isn't available (-EBUSY)
e. Unlock with uverbs_unlock_object (implemented in this patch)
f. Release up_read(&file->close_sem)
Disassociate/process destruction:
* In disassociate, do thee following for every process
1. Grab down_write(&file->close_sem)
2. Release all objects from context, ordered by type list (call free
function the driver has specified)
3. Release up_write(&file->close_sem)
ib_uobjects are lockless. If two commands are executed in
parallel and one need exclusive access (WRITE/DESTROY) -> one
command will fail. User-space needs to either synchronize or do
something productive with the failure.
Signed-off-by: Matan Barak <matanb@xxxxxxxxxxxx>
Signed-off-by: Haggai Eran <haggaie@xxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
---
drivers/infiniband/core/uidr.c | 11 +-----
drivers/infiniband/core/uobject.c | 6 +--
drivers/infiniband/core/uobject.h | 4 +-
drivers/infiniband/core/uverbs_cmd.c | 72 +++++++++++++++---------------------
include/rdma/ib_verbs.h | 1 -
5 files changed, 35 insertions(+), 59 deletions(-)
diff --git a/drivers/infiniband/core/uidr.c b/drivers/infiniband/core/uidr.c
index 72c4c77..6018717 100644
--- a/drivers/infiniband/core/uidr.c
+++ b/drivers/infiniband/core/uidr.c
@@ -88,7 +88,7 @@ struct ib_uobject *uverbs_get_type_from_idr(struct uverbs_uobject_type *type,
if (!uobj)
return ERR_PTR(-ENOMEM);
- init_uobj(uobj, 0, ucontext, &type->lock_class);
+ init_uobj(uobj, 0, ucontext);
/* lock idr */
ret = ib_uverbs_uobject_add(uobj, type);
@@ -213,10 +213,6 @@ static struct ib_uobject *idr_read_uobj(int id, struct ib_ucontext *context,
if (!uobj)
return NULL;
- if (nested)
- down_read_nested(&uobj->mutex, SINGLE_DEPTH_NESTING);
- else
- down_read(&uobj->mutex);
if (!uobj->live) {
put_uobj_read(uobj);
return NULL;
@@ -233,11 +229,8 @@ struct ib_uobject *idr_write_uobj(int id, struct ib_ucontext *context)
if (!uobj)
return NULL;
- down_write(&uobj->mutex);
- if (!uobj->live) {
- put_uobj_write(uobj);
+ if (!uobj->live)
return NULL;
- }
return uobj;
}
diff --git a/drivers/infiniband/core/uobject.c b/drivers/infiniband/core/uobject.c
index c3d1098..ed862e8 100644
--- a/drivers/infiniband/core/uobject.c
+++ b/drivers/infiniband/core/uobject.c
@@ -179,13 +179,11 @@ void ib_uverbs_uobject_enable(struct ib_uobject *uobject)
*/
void init_uobj(struct ib_uobject *uobj, u64 user_handle,
- struct ib_ucontext *context, struct uverbs_lock_class *c)
+ struct ib_ucontext *context)
{
uobj->user_handle = user_handle;
uobj->context = context;
kref_init(&uobj->ref);
- init_rwsem(&uobj->mutex);
- lockdep_set_class_and_name(&uobj->mutex, &c->key, c->name);
uobj->live = 0;
}
@@ -201,12 +199,10 @@ void put_uobj(struct ib_uobject *uobj)
void put_uobj_read(struct ib_uobject *uobj)
{
- up_read(&uobj->mutex);
put_uobj(uobj);
}
void put_uobj_write(struct ib_uobject *uobj)
{
- up_write(&uobj->mutex);
put_uobj(uobj);
}
diff --git a/drivers/infiniband/core/uobject.h b/drivers/infiniband/core/uobject.h
index 13fdaef..3514a1b 100644
--- a/drivers/infiniband/core/uobject.h
+++ b/drivers/infiniband/core/uobject.h
@@ -48,12 +48,12 @@ struct uverbs_uobject_type {
struct ib_uobject *uobject,
struct ib_ucontext *ucontext);
u16 obj_type;
- struct uverbs_lock_class lock_class;
};
/* embed in ucontext per type */
struct uverbs_uobject_list {
struct uverbs_uobject_type *type;
+ /* TODO: replace with hash for faster access */
struct list_head list;
struct list_head type_list;
};
@@ -64,7 +64,7 @@ void ib_uverbs_uobject_remove(struct ib_uobject *uobject);
void ib_uverbs_uobject_enable(struct ib_uobject *uobject);
void init_uobj(struct ib_uobject *uobj, u64 user_handle,
- struct ib_ucontext *context, struct uverbs_lock_class *c);
+ struct ib_ucontext *context);
void release_uobj(struct kref *kref);
void put_uobj(struct ib_uobject *uobj);
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 22406fe..148e26e 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -46,16 +46,6 @@
#include "core_priv.h"
-static struct uverbs_lock_class pd_lock_class = { .name = "PD-uobj" };
-static struct uverbs_lock_class mr_lock_class = { .name = "MR-uobj" };
-static struct uverbs_lock_class mw_lock_class = { .name = "MW-uobj" };
-static struct uverbs_lock_class cq_lock_class = { .name = "CQ-uobj" };
-static struct uverbs_lock_class qp_lock_class = { .name = "QP-uobj" };
-static struct uverbs_lock_class ah_lock_class = { .name = "AH-uobj" };
-static struct uverbs_lock_class srq_lock_class = { .name = "SRQ-uobj" };
-static struct uverbs_lock_class xrcd_lock_class = { .name = "XRCD-uobj" };
-static struct uverbs_lock_class rule_lock_class = { .name = "RULE-uobj" };
-
ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
struct ib_device *ib_dev,
const char __user *buf,
@@ -308,8 +298,8 @@ ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
if (!uobj)
return -ENOMEM;
- init_uobj(uobj, 0, file->ucontext, &pd_lock_class);
- down_write(&uobj->mutex);
+ down_read(&file->close_sem);
+ init_uobj(uobj, 0, file->ucontext);
pd = ib_dev->alloc_pd(ib_dev, file->ucontext, &udata);
if (IS_ERR(pd)) {
@@ -342,7 +332,7 @@ ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
uobj->live = 1;
- up_write(&uobj->mutex);
+ up_read(&file->close_sem);
return in_len;
@@ -543,9 +533,8 @@ ssize_t ib_uverbs_open_xrcd(struct ib_uverbs_file *file,
goto err_tree_mutex_unlock;
}
- init_uobj(&obj->uobject, 0, file->ucontext, &xrcd_lock_class);
-
- down_write(&obj->uobject.mutex);
+ down_read(&file->close_sem);
+ init_uobj(&obj->uobject, 0, file->ucontext);
if (!xrcd) {
xrcd = ib_dev->alloc_xrcd(ib_dev, file->ucontext, &udata);
@@ -595,7 +584,7 @@ ssize_t ib_uverbs_open_xrcd(struct ib_uverbs_file *file,
mutex_unlock(&file->mutex);
obj->uobject.live = 1;
- up_write(&obj->uobject.mutex);
+ up_read(&file->close_sem);
mutex_unlock(&file->device->xrcd_tree_mutex);
return in_len;
@@ -737,8 +726,8 @@ ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
if (!uobj)
return -ENOMEM;
- init_uobj(uobj, 0, file->ucontext, &mr_lock_class);
- down_write(&uobj->mutex);
+ down_read(&file->close_sem);
+ init_uobj(uobj, 0, file->ucontext);
pd = idr_read_pd(cmd.pd_handle, file->ucontext);
if (!pd) {
@@ -791,7 +780,7 @@ ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
uobj->live = 1;
- up_write(&uobj->mutex);
+ up_read(&file->close_sem);
return in_len;
@@ -959,8 +948,8 @@ ssize_t ib_uverbs_alloc_mw(struct ib_uverbs_file *file,
if (!uobj)
return -ENOMEM;
- init_uobj(uobj, 0, file->ucontext, &mw_lock_class);
- down_write(&uobj->mutex);
+ down_read(&file->close_sem);
+ init_uobj(uobj, 0, file->ucontext);
pd = idr_read_pd(cmd.pd_handle, file->ucontext);
if (!pd) {
@@ -1007,7 +996,7 @@ ssize_t ib_uverbs_alloc_mw(struct ib_uverbs_file *file,
uobj->live = 1;
- up_write(&uobj->mutex);
+ up_read(&file->close_sem);
return in_len;
@@ -1129,8 +1118,8 @@ static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
if (!obj)
return ERR_PTR(-ENOMEM);
- init_uobj(&obj->uobject, cmd->user_handle, file->ucontext, &cq_lock_class);
- down_write(&obj->uobject.mutex);
+ down_read(&file->close_sem);
+ init_uobj(&obj->uobject, cmd->user_handle, file->ucontext);
if (cmd->comp_channel >= 0) {
ev_file = ib_uverbs_lookup_comp_file(cmd->comp_channel);
@@ -1188,7 +1177,7 @@ static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
obj->uobject.live = 1;
- up_write(&obj->uobject.mutex);
+ up_read(&file->close_sem);
return obj;
@@ -1530,9 +1519,8 @@ static int create_qp(struct ib_uverbs_file *file,
if (!obj)
return -ENOMEM;
- init_uobj(&obj->uevent.uobject, cmd->user_handle, file->ucontext,
- &qp_lock_class);
- down_write(&obj->uevent.uobject.mutex);
+ down_read(&file->close_sem);
+ init_uobj(&obj->uevent.uobject, cmd->user_handle, file->ucontext);
if (cmd->qp_type == IB_QPT_XRC_TGT) {
xrcd = idr_read_xrcd(cmd->pd_handle, file->ucontext,
@@ -1692,7 +1680,7 @@ static int create_qp(struct ib_uverbs_file *file,
obj->uevent.uobject.live = 1;
- up_write(&obj->uevent.uobject.mutex);
+ up_read(&file->close_sem);
return 0;
err_cb:
@@ -1853,8 +1841,8 @@ ssize_t ib_uverbs_open_qp(struct ib_uverbs_file *file,
if (!obj)
return -ENOMEM;
- init_uobj(&obj->uevent.uobject, cmd.user_handle, file->ucontext, &qp_lock_class);
- down_write(&obj->uevent.uobject.mutex);
+ down_read(&file->close_sem);
+ init_uobj(&obj->uevent.uobject, cmd.user_handle, file->ucontext);
xrcd = idr_read_xrcd(cmd.pd_handle, file->ucontext, &xrcd_uobj);
if (!xrcd) {
@@ -1904,7 +1892,7 @@ ssize_t ib_uverbs_open_qp(struct ib_uverbs_file *file,
obj->uevent.uobject.live = 1;
- up_write(&obj->uevent.uobject.mutex);
+ up_read(&file->close_sem);
return in_len;
@@ -2593,8 +2581,8 @@ ssize_t ib_uverbs_create_ah(struct ib_uverbs_file *file,
if (!uobj)
return -ENOMEM;
- init_uobj(uobj, cmd.user_handle, file->ucontext, &ah_lock_class);
- down_write(&uobj->mutex);
+ down_read(&file->close_sem);
+ init_uobj(uobj, cmd.user_handle, file->ucontext);
pd = idr_read_pd(cmd.pd_handle, file->ucontext);
if (!pd) {
@@ -2644,7 +2632,7 @@ ssize_t ib_uverbs_create_ah(struct ib_uverbs_file *file,
uobj->live = 1;
- up_write(&uobj->mutex);
+ up_read(&file->close_sem);
return in_len;
@@ -2904,8 +2892,8 @@ int ib_uverbs_ex_create_flow(struct ib_uverbs_file *file,
err = -ENOMEM;
goto err_free_attr;
}
- init_uobj(uobj, 0, file->ucontext, &rule_lock_class);
- down_write(&uobj->mutex);
+ down_read(&file->close_sem);
+ init_uobj(uobj, 0, file->ucontext);
qp = idr_read_qp(cmd.qp_handle, file->ucontext);
if (!qp) {
@@ -2975,7 +2963,7 @@ int ib_uverbs_ex_create_flow(struct ib_uverbs_file *file,
uobj->live = 1;
- up_write(&uobj->mutex);
+ up_read(&file->close_sem);
kfree(flow_attr);
if (cmd.flow_attr.num_of_specs)
kfree(kern_flow_attr);
@@ -3055,8 +3043,8 @@ static int __uverbs_create_xsrq(struct ib_uverbs_file *file,
if (!obj)
return -ENOMEM;
- init_uobj(&obj->uevent.uobject, cmd->user_handle, file->ucontext, &srq_lock_class);
- down_write(&obj->uevent.uobject.mutex);
+ down_read(&file->close_sem);
+ init_uobj(&obj->uevent.uobject, cmd->user_handle, file->ucontext);
if (cmd->srq_type == IB_SRQT_XRC) {
attr.ext.xrc.xrcd = idr_read_xrcd(cmd->xrcd_handle, file->ucontext, &xrcd_uobj);
@@ -3144,7 +3132,7 @@ static int __uverbs_create_xsrq(struct ib_uverbs_file *file,
obj->uevent.uobject.live = 1;
- up_write(&obj->uevent.uobject.mutex);
+ up_read(&file->close_sem);
return 0;
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index e402473..84d72d2 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1356,7 +1356,6 @@ struct ib_uobject {
int id; /* index into kernel idr */
struct kref ref;
atomic_t usecnt;
- struct rw_semaphore mutex; /* protects .live */
struct rcu_head rcu; /* kfree_rcu() overhead */
int live;
/* List of object under uverbs_object_type */
--
2.5.0
--
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