[PATCH rdma-next 03/10] RDMA/core: Remove ucontext_lock from the uverbs_destry_ufile_hw() path

Yishai Hadas
2020-01-08T18:06:30Z

From: Jason Gunthorpe <jgg@mellanox.com>

This lock only serializes ucontext creation. Instead of checking the
ucontext_lock during destruction hold the existing hw_destroy_rwsem
during creation, which is the standard pattern for object creation.

The simplification of locking is needed for the next patch.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
---
drivers/infiniband/core/rdma_core.c | 21 +--------------------
drivers/infiniband/core/uverbs_cmd.c | 5 ++++-
2 files changed, 5 insertions(+), 21 deletions(-)

diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
index f839b93..58af6a7 100644
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -863,9 +863,7 @@ static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,
}

/*
- * Destroy the uncontext and every uobject associated with it. If called with
- * reason != RDMA_REMOVE_CLOSE this will not return until the destruction has
- * been completed and ufile->ucontext is NULL.
+ * Destroy the uncontext and every uobject associated with it.
*
* This is internally locked and can be called in parallel from multiple
* contexts.
@@ -873,22 +871,6 @@ static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,
void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile,
enum rdma_remove_reason reason)
{
- if (reason == RDMA_REMOVE_CLOSE) {
- /*
- * During destruction we might trigger something that
- * synchronously calls release on any file descriptor. For
- * this reason all paths that come from file_operations
- * release must use try_lock. They can progress knowing that
- * there is an ongoing uverbs_destroy_ufile_hw that will clean
- * up the driver resources.
- */
- if (!mutex_trylock(&ufile->ucontext_lock))
- return;
-
- } else {
- mutex_lock(&ufile->ucontext_lock);
- }
-
down_write(&ufile->hw_destroy_rwsem);

/*
@@ -917,7 +899,6 @@ void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile,

done:
up_write(&ufile->hw_destroy_rwsem);
- mutex_unlock(&ufile->ucontext_lock);
}

const struct uverbs_obj_type_class uverbs_fd_class = {
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 29b1b5a..d71ffe4 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -218,6 +218,8 @@ static int ib_uverbs_get_context(struct uverbs_attr_bundle *attrs)
if (ret)
return ret;

+ if (!down_read_trylock(&file->hw_destroy_rwsem))
+ return -EIO;
mutex_lock(&file->ucontext_lock);
ib_dev = srcu_dereference(file->device->ib_dev,
&file->device->disassociate_srcu);
@@ -284,7 +286,7 @@ static int ib_uverbs_get_context(struct uverbs_attr_bundle *attrs)
smp_store_release(&file->ucontext, ucontext);

mutex_unlock(&file->ucontext_lock);
-
+ up_read(&file->hw_destroy_rwsem);
return 0;

err_uobj:
@@ -298,6 +300,7 @@ static int ib_uverbs_get_context(struct uverbs_attr_bundle *attrs)

err:
mutex_unlock(&file->ucontext_lock);
+ up_read(&file->hw_destroy_rwsem);
return ret;
}

--
1.8.3.1