mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-25 19:15:19 +07:00
bd0abfa8ca
Update the document since those functions had been renamed in below. Fixes:0a18cfe4f6("IB/core: Rename ib_create_ah to rdma_create_ah") Fixes:67b985b6c7("IB/core: Rename ib_modify_ah to rdma_modify_ah") Fixes:bfbfd661c9("IB/core: Rename ib_query_ah to rdma_query_ah") Fixes:3652315934("IB/core: Rename ib_destroy_ah to rdma_destroy_ah") Link: https://lore.kernel.org/r/20190903124519.28318-1-guoqing.jiang@cloud.ionos.com Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
119 lines
4.1 KiB
ReStructuredText
119 lines
4.1 KiB
ReStructuredText
===========================
|
|
InfiniBand Midlayer Locking
|
|
===========================
|
|
|
|
This guide is an attempt to make explicit the locking assumptions
|
|
made by the InfiniBand midlayer. It describes the requirements on
|
|
both low-level drivers that sit below the midlayer and upper level
|
|
protocols that use the midlayer.
|
|
|
|
Sleeping and interrupt context
|
|
==============================
|
|
|
|
With the following exceptions, a low-level driver implementation of
|
|
all of the methods in struct ib_device may sleep. The exceptions
|
|
are any methods from the list:
|
|
|
|
- create_ah
|
|
- modify_ah
|
|
- query_ah
|
|
- destroy_ah
|
|
- post_send
|
|
- post_recv
|
|
- poll_cq
|
|
- req_notify_cq
|
|
- map_phys_fmr
|
|
|
|
which may not sleep and must be callable from any context.
|
|
|
|
The corresponding functions exported to upper level protocol
|
|
consumers:
|
|
|
|
- rdma_create_ah
|
|
- rdma_modify_ah
|
|
- rdma_query_ah
|
|
- rdma_destroy_ah
|
|
- ib_post_send
|
|
- ib_post_recv
|
|
- ib_req_notify_cq
|
|
- ib_map_phys_fmr
|
|
|
|
are therefore safe to call from any context.
|
|
|
|
In addition, the function
|
|
|
|
- ib_dispatch_event
|
|
|
|
used by low-level drivers to dispatch asynchronous events through
|
|
the midlayer is also safe to call from any context.
|
|
|
|
Reentrancy
|
|
----------
|
|
|
|
All of the methods in struct ib_device exported by a low-level
|
|
driver must be fully reentrant. The low-level driver is required to
|
|
perform all synchronization necessary to maintain consistency, even
|
|
if multiple function calls using the same object are run
|
|
simultaneously.
|
|
|
|
The IB midlayer does not perform any serialization of function calls.
|
|
|
|
Because low-level drivers are reentrant, upper level protocol
|
|
consumers are not required to perform any serialization. However,
|
|
some serialization may be required to get sensible results. For
|
|
example, a consumer may safely call ib_poll_cq() on multiple CPUs
|
|
simultaneously. However, the ordering of the work completion
|
|
information between different calls of ib_poll_cq() is not defined.
|
|
|
|
Callbacks
|
|
---------
|
|
|
|
A low-level driver must not perform a callback directly from the
|
|
same callchain as an ib_device method call. For example, it is not
|
|
allowed for a low-level driver to call a consumer's completion event
|
|
handler directly from its post_send method. Instead, the low-level
|
|
driver should defer this callback by, for example, scheduling a
|
|
tasklet to perform the callback.
|
|
|
|
The low-level driver is responsible for ensuring that multiple
|
|
completion event handlers for the same CQ are not called
|
|
simultaneously. The driver must guarantee that only one CQ event
|
|
handler for a given CQ is running at a time. In other words, the
|
|
following situation is not allowed::
|
|
|
|
CPU1 CPU2
|
|
|
|
low-level driver ->
|
|
consumer CQ event callback:
|
|
/* ... */
|
|
ib_req_notify_cq(cq, ...);
|
|
low-level driver ->
|
|
/* ... */ consumer CQ event callback:
|
|
/* ... */
|
|
return from CQ event handler
|
|
|
|
The context in which completion event and asynchronous event
|
|
callbacks run is not defined. Depending on the low-level driver, it
|
|
may be process context, softirq context, or interrupt context.
|
|
Upper level protocol consumers may not sleep in a callback.
|
|
|
|
Hot-plug
|
|
--------
|
|
|
|
A low-level driver announces that a device is ready for use by
|
|
consumers when it calls ib_register_device(), all initialization
|
|
must be complete before this call. The device must remain usable
|
|
until the driver's call to ib_unregister_device() has returned.
|
|
|
|
A low-level driver must call ib_register_device() and
|
|
ib_unregister_device() from process context. It must not hold any
|
|
semaphores that could cause deadlock if a consumer calls back into
|
|
the driver across these calls.
|
|
|
|
An upper level protocol consumer may begin using an IB device as
|
|
soon as the add method of its struct ib_client is called for that
|
|
device. A consumer must finish all cleanup and free all resources
|
|
relating to a device before returning from the remove method.
|
|
|
|
A consumer is permitted to sleep in its add and remove methods.
|