[v3,00/22] enable hotplug on multi-process
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Message ID 20180625071745.16810-1-qi.z.zhang@intel.com
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  • enable hotplug on multi-process
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Qi Zhang June 25, 2018, 7:17 a.m. UTC
v3:
- enable mp init callback register to help non-eal module to initialize
  mp channel during rte_eal_init
- fix when attach share device from secondary.
  1) dead lock due to sync IPC be invoked in rte_malloc in primary
     process when handle secondary request to attach device, the
     solution is primary process to issue share device attach/detach
     in interrupt thread.
  2) return port_id not correct.
- check nb_sent and nb_received in sync IPC.
- fix memory leak duirng error handling at attach_on_secondary.
- improve clean_lock_callback to only lock/unlock spinlock once
- improve error code return in check-reply during async IPC.
- remove rte_ prefix of internal function in ethdev_mp.c
- sample code improvement.
  1) rename sample to "hotplug_mp", and move to example/multi-process.
  2) cleanup header include.
  3) call rte_eal_cleanup before exit.

v2:
- rename rte_ethdev_mp.* to ethdev_mp.*
- rename rte_ethdev_lock.* to ethdev_lock.*
- move internal funciton to ethdev_private.h
- separate rte_eth_dev_[un]lock into rte_eth_dev_[un]lock and
  rte_eth_dev_[un]lock_with_callback
- lock callbacks will be removed automatically after device is detached.
- add experimental tag for all new APIs.
- fix coding style issue.
- fix wrong lisence header in sample code.
- fix spelling 
- fix meson.build.
- improve comments. 

Background:
===========

Currently secondary process will only sync ethdev from primary
process at init stage, but it will not be aware if device
is attached/detached on primary process at runtime.

While there is the requirement from application that take
primary-secondary process model. The primary process work as a
resource management process, it will create/destroy virtual device
at runtime, while the secondary process deal with the network stuff
with these devices.

Solution:
=========

So the orignial intention is to fix this gap, but beyond that
the patch set provide a more comprehesive solution to handle
different hotplug cases in multi-process situation, it cover below
scenario:

1. Attach a share device from primary
2. Detach a share device from primary
3. Attach a share device from secondary
4. Detach a share device from secondary
5. Attach a private device from secondary
6. Detach a private device from secondary
7. Detach a share device from secondary privately
8. Attach a share device from secondary privately

In primary-secondary process model, we assume ethernet devices are
shared by default. that means attach or detach a device on any process
will broadcast to all other processes through mp channel then device
information will be synchronized on all processes.

Any failure during attaching process will cause inconsistent status
between processes, so proper rollback action should be considered.
Also, it is not safe to detach a share device when other process still
use it, so a handshake mechanism is introduced.

Scenario for Case 1, 2:

attach device from primary
a) primary attach the new device if failed goto h).
b) primary send attach sync request to all secondary.
c) secondary receive request and attach device and send reply.
d) primary check the reply if all success go to i).
e) primary send attach rollback sync request to all secondary.
f) secondary receive the request and detach device and send reply.
g) primary receive the reply and detach device as rollback action.
h) attach fail
i) attach success

detach device from primary
a) primary perform pre-detach check, if device is locked, goto i).
b) primary send pre-detach sync request to all secondary.
c) secondary perform pre-detach check and send reply.
d) primary check the reply if any fail goto i).
e) primary send detach sync request to all secondary
f) secondary detach the device and send reply (assume no fail)
g) primary detach the device.
h) detach success
i) detach failed

Scenario for case 3, 4:

attach device from secondary:
a) seconary send asycn request to primary and wait on a condition
   which will be released by matched response from primary.
b) primary receive the request and attach the new device if failed
   goto i).
c) primary forward attach request to all secondary as async request
   (because this in mp thread context, use sync request will deadlock,
    same reason for all following async request.)
d) secondary receive request and attach device and send reply.
e) primary check the reply if all success go to j).
f) primary send attach rollback async request to all secondary.
g) secondary receive the request and detach device and send reply.
h) primary receive the reply and detach device as rollback action.
i) send fail response to secondary, goto k).
j) send success response to secondary.
k) secondary process receive response and return.
 
detach device from secondary:
a) secondary send async request to primary and wait on a condition
   which will be released by matched response from primary.
b) primary receive the request and  perform pre-detach check, if device
   is locked, goto j).
c) primary send pre-detach async request to all secondary.
d) secondary perform pre-detach check and send reply.
e) primary check the reply if any fail goto j).
f) primary send detach async request to all secondary
g) secondary detach the device and send reply
h) primary detach the device.
i) send success response to secondary, goto k).
j) send fail response to secondary.
k) secondary process receive response and return.

Case 5, 6:
Secondary process can attach private device which only visible to
itself, in this case no IPC is involved, primary process is not allowed
to have private device so far.

Case 7, 8:
Secondary process can also temporally to detach a share device
"privately" then attach it back later, this action also not impact other
processes.

APIs chenages:
==============

rte_eth_dev_attach and rte_eth_dev_attach are extended to support
share device attach/detach in primary-secondary process model, it will
be called in case 1,2,3,4.

New API rte_eth_dev_attach_private and rte_eth_dev_detach_private are
introduced to cover case 5,6,7,8, this API can only be invoked in
secondary process.

New API rte_eth_dev_lock and rte_eth_dev_unlock are introduced to let
application lock or unlock on specific ethdev, a locked device
can't be detached. This help applicaiton to prevent unexpected
device detaching, especially in multi-process envrionment.
Aslo the new API let application to register a callback function
which will be invoked before a device is going to be detached,
the return value of the function will decide if device will continue
be detached or not, this support application to do condition check
at runtime.

PMD Impact:
===========

Currently device removing is not handled well in secondary process on
most pmd drivers, rte_eth_dev_relase_port will be invoked and will mess up
primary process since it reset all shared data. So we introduced new API
rte_eth_dev_release_port_local which only reset ethdev's state to unsued
but not touch shared data so other process will not be impacted.
Since not all device driver is target to support primary-secondary
process model, so the patch set only fix this on all Intel devices and
vdev, it can be refereneced by other driver when equevalent fix is
required

Limitation:
===========

1. The solution does not cover the case that primary process exit while
   secondary processes still be active. Though this is not a typial use
   case, but if this happens:
   a. secondary process can't attach / detach any shared device since no
      primary exist.
   b. secondary process still can attach / detach private device.
   c. secondary process still can detach a share device privately but may
      not attach it back, that ethdev slot will become zombie slot.

2. So for, for PCI bus, case 5,6 is not supported. PCI bus scan/probe
   mechanism can be improved to support attach private device on secondary
   process, but this is not the scope of this patchset.

Example:
========

The patchset also contains a example to demonstrate device hotplug
in multi-process model, below are detail instructions.

/* start sample code as primary then secondary */
./hotplug_mp --proc-type=auto

Command Line Example:

>help
>list

/* attach a af_packet vdev */
>attach net_af_packet,iface=eth0

/* detach port 0 */
>detach 0

/* attach a private af_packet vdev (secondary process only)*/
>attachp net_af_packet,iface=eth0

/* detach a private device (secondary process only) */
>detachp 0

/* lock port 0 */
>lock 0

/* unlock port 0 */
>unlock 0

Qi Zhang (23):
  eal: introduce one device scan
  bus/vdev: enable one device scan
  ethdev: add function to release port in local process
  eal: enable multi process init callback
  ethdev: enable hotplug on multi-process
  ethdev: introduce device lock
  ethdev: support attach or detach share device from secondary
  net/i40e: enable port detach on secondary process
  net/ixgbe: enable port detach on secondary process
  net/e1000: enable port detach on secondary process
  net/igb: enable port detach on secondary process
  net/fm10k: enable port detach on secondary process
  net/af_packet: enable port detach on secondary process
  net/bonding: enable port detach on secondary process
  net/failsafe: enable port detach on secondary process
  net/kni: enable port detach on secondary process
  net/null: enable port detach on secondary process
  net/octeontx: enable port detach on secondary process
  net/pcap: enable port detach on secondary process
  net/softnic: enable port detach on secondary process
  net/tap: enable port detach on secondary process
  net/vhost: enable port detach on secondary process
  examples/multi_process: add hotplug sample

 drivers/bus/vdev/vdev.c                      |  30 ++
 drivers/net/af_packet/rte_eth_af_packet.c    |  11 +
 drivers/net/bonding/rte_eth_bond_pmd.c       |  11 +
 drivers/net/e1000/em_ethdev.c                |   9 +
 drivers/net/e1000/igb_ethdev.c               |   9 +
 drivers/net/failsafe/failsafe.c              |  16 +
 drivers/net/fm10k/fm10k_ethdev.c             |   9 +
 drivers/net/i40e/i40e_ethdev.c               |   2 +
 drivers/net/i40e/i40e_ethdev_vf.c            |   9 +
 drivers/net/ixgbe/ixgbe_ethdev.c             |  12 +
 drivers/net/kni/rte_eth_kni.c                |  11 +
 drivers/net/null/rte_eth_null.c              |  16 +-
 drivers/net/octeontx/octeontx_ethdev.c       |  16 +
 drivers/net/pcap/rte_eth_pcap.c              |  15 +-
 drivers/net/softnic/rte_eth_softnic.c        |  19 +-
 drivers/net/tap/rte_eth_tap.c                |  17 +-
 drivers/net/vhost/rte_eth_vhost.c            |  11 +
 examples/multi_process/Makefile              |   1 +
 examples/multi_process/hotplug_mp/Makefile   |  23 +
 examples/multi_process/hotplug_mp/commands.c | 356 +++++++++++++
 examples/multi_process/hotplug_mp/commands.h |  10 +
 examples/multi_process/hotplug_mp/main.c     |  41 ++
 lib/librte_eal/common/eal_common_dev.c       |  17 +-
 lib/librte_eal/common/eal_common_proc.c      |  51 +-
 lib/librte_eal/common/eal_private.h          |   5 +
 lib/librte_eal/common/include/rte_bus.h      |  16 +
 lib/librte_eal/common/include/rte_eal.h      |  34 ++
 lib/librte_eal/linuxapp/eal/eal.c            |   2 +
 lib/librte_ethdev/Makefile                   |   2 +
 lib/librte_ethdev/ethdev_lock.c              | 140 ++++++
 lib/librte_ethdev/ethdev_lock.h              |  31 ++
 lib/librte_ethdev/ethdev_mp.c                | 714 +++++++++++++++++++++++++++
 lib/librte_ethdev/ethdev_mp.h                |  42 ++
 lib/librte_ethdev/ethdev_private.h           |  39 ++
 lib/librte_ethdev/meson.build                |   2 +
 lib/librte_ethdev/rte_ethdev.c               | 272 +++++++++-
 lib/librte_ethdev/rte_ethdev.h               | 169 +++++++
 lib/librte_ethdev/rte_ethdev_core.h          |   5 +
 lib/librte_ethdev/rte_ethdev_driver.h        |  13 +
 39 files changed, 2176 insertions(+), 32 deletions(-)
 create mode 100644 examples/multi_process/hotplug_mp/Makefile
 create mode 100644 examples/multi_process/hotplug_mp/commands.c
 create mode 100644 examples/multi_process/hotplug_mp/commands.h
 create mode 100644 examples/multi_process/hotplug_mp/main.c
 create mode 100644 lib/librte_ethdev/ethdev_lock.c
 create mode 100644 lib/librte_ethdev/ethdev_lock.h
 create mode 100644 lib/librte_ethdev/ethdev_mp.c
 create mode 100644 lib/librte_ethdev/ethdev_mp.h
 create mode 100644 lib/librte_ethdev/ethdev_private.h