[v11,00/10] eal: Add EAL API for threading

From: Narcisa Vasile <navasile@microsoft.com>

EAL thread API

**Problem Statement**
DPDK currently uses the pthread interface to create and manage threads.
Windows does not support the POSIX thread programming model,
so it currently
relies on a header file that hides the Windows calls under
pthread matched interfaces. Given that EAL should isolate the environment
specifics from the applications and libraries and mediate
all the communication with the operating systems, a new EAL interface
is needed for thread management.

**Goals**
* Introduce a generic EAL API for threading support that will remove
  the current Windows pthread.h shim.
* Replace references to pthread_* across the DPDK codebase with the new
  RTE_THREAD_* API.
* Allow users to choose between using the RTE_THREAD_* API or a
  3rd party thread library through a configuration option.

**Design plan**
New API main files:
* rte_thread.h (librte_eal/include)
* rte_thread.c (librte_eal/windows)
* rte_thread.c (librte_eal/common)

**A schematic example of the design**
--------------------------------------------------
lib/librte_eal/include/rte_thread.h
int rte_thread_create();

lib/librte_eal/common/rte_thread.c
int rte_thread_create() 
{
	return pthread_create();
}

lib/librte_eal/windows/rte_thread.c
int rte_thread_create() 
{
	return CreateThread();
}
-----------------------------------------------------

**Thread attributes**

When or after a thread is created, specific characteristics of the thread
can be adjusted. Given that the thread characteristics that are of interest
for DPDK applications are affinity and priority, the following structure
that represents thread attributes has been defined:

typedef struct
{
	enum rte_thread_priority priority;
	rte_cpuset_t cpuset;
} rte_thread_attr_t;

The *rte_thread_create()* function can optionally receive
an rte_thread_attr_t
object that will cause the thread to be created with the
affinity and priority
described by the attributes object. If no rte_thread_attr_t is passed
(parameter is NULL), the default affinity and priority are used.
An rte_thread_attr_t object can also be set to the default values
by calling *rte_thread_attr_init()*.

*Priority* is represented through an enum that currently advertises
two values for priority:
	- RTE_THREAD_PRIORITY_NORMAL
	- RTE_THREAD_PRIORITY_REALTIME_CRITICAL
The enum can be extended to allow for multiple priority levels.
rte_thread_set_priority      - sets the priority of a thread
rte_thread_attr_set_priority - updates an rte_thread_attr_t object
                               with a new value for priority

The user can choose thread priority through an EAL parameter,
when starting an application.  If EAL parameter is not used,
the per-platform default value for thread priority is used.
Otherwise administrator has an option to set one of available options:
 --thread-prio normal
 --thread-prio realtime

Example:
./dpdk-l2fwd -l 0-3 -n 4 –thread-prio normal -- -q 8 -p ffff

*Affinity* is described by the already known “rte_cpuset_t” type.
rte_thread_attr_set/get_affinity - sets/gets the affinity field in a
                                   rte_thread_attr_t object
rte_thread_set/get_affinity      – sets/gets the affinity of a thread

**Errors**
A translation function that maps Windows error codes to errno-style
error codes is provided. 

**Future work**
The long term plan is for EAL to provide full threading support:
* Add support for conditional variables
* Add support for pthread_mutex_trylock
* Additional functionality offered by pthread_*
  (such as pthread_setname_np, etc.)

v11:
 - Add unit tests for thread API
 - Rebase

v10:
 - Remove patch no. 10. It will be broken down in subpatches 
   and sent as a different patchset that depends on this one.
   This is done due to the ABI breaks that would be caused by patch 10.
 - Replace unix/rte_thread.c with common/rte_thread.c
 - Remove initializations that may prevent compiler from issuing useful
   warnings.
 - Remove rte_thread_types.h and rte_windows_thread_types.h
 - Remove unneeded priority macros (EAL_THREAD_PRIORITY*)
 - Remove functions that retrieves thread handle from process handle
 - Remove rte_thread_cancel() until same behavior is obtained on
   all platforms.
 - Fix rte_thread_detach() function description,
   return value and remove empty line.
 - Reimplement mutex functions. Add compatible representation for mutex
   identifier. Add macro to replace static mutex initialization instances.
 - Fix commit messages (lines too long, remove unicode symbols)

v9:
- Sign patches

v8:
- Rebase
- Add rte_thread_detach() API
- Set default priority, when user did not specify a value

v7:
Based on DmitryK's review:
- Change thread id representation
- Change mutex id representation
- Implement static mutex inititalizer for Windows
- Change barrier identifier representation
- Improve commit messages
- Add missing doxygen comments
- Split error translation function
- Improve name for affinity function
- Remove cpuset_size parameter
- Fix eal_create_cpu_map function
- Map EAL priority values to OS specific values
- Add thread wrapper for start routine
- Do not export rte_thread_cancel() on Windows
- Cleanup, fix comments, fix typos.

v6:
- improve error-translation function
- call the error translation function in rte_thread_value_get()

v5:
- update cover letter with more details on the priority argument

v4:
- fix function description
- rebase

v3:
- rebase

v2:
- revert changes that break ABI 
- break up changes into smaller patches
- fix coding style issues
- fix issues with errors
- fix parameter type in examples/kni.c


Narcisa Vasile (10):
  eal: add basic threading functions
  eal: add thread attributes
  eal/windows: translate Windows errors to errno-style errors
  eal: implement functions for thread affinity management
  eal: implement thread priority management functions
  eal: add thread lifetime management
  eal: implement functions for mutex management
  eal: implement functions for thread barrier management
  eal: add EAL argument for setting thread priority
  Add unit tests for thread API

 app/test/meson.build                |   2 +
 app/test/test_threads.c             | 419 ++++++++++++++++++++
 lib/eal/common/eal_common_options.c |  28 +-
 lib/eal/common/eal_internal_cfg.h   |   2 +
 lib/eal/common/eal_options.h        |   2 +
 lib/eal/common/meson.build          |   1 +
 lib/eal/common/rte_thread.c         | 445 +++++++++++++++++++++
 lib/eal/include/rte_thread.h        | 406 ++++++++++++++++++-
 lib/eal/unix/meson.build            |   1 -
 lib/eal/unix/rte_thread.c           |  92 -----
 lib/eal/version.map                 |  20 +
 lib/eal/windows/eal_lcore.c         | 176 ++++++---
 lib/eal/windows/eal_windows.h       |  10 +
 lib/eal/windows/include/sched.h     |   2 +-
 lib/eal/windows/rte_thread.c        | 588 ++++++++++++++++++++++++++--
 15 files changed, 2020 insertions(+), 174 deletions(-)
 create mode 100644 app/test/test_threads.c
 create mode 100644 lib/eal/common/rte_thread.c
 delete mode 100644 lib/eal/unix/rte_thread.c