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lib: streamline frr_pthreads, add default loop

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Some work on FRR's pthread wrapper.

* Provide a built-in way to synchronize thread startup
* Make utility functions take frr_pthread * instead of its integer ID
* Pass frr_pthread * as pthread start function argument
* Correct some comment styling
* Rename some variables to match naming conventions in the file
* Change parameter ordering in stop function prototype to follow the
  convention in the other functions
* Default new frr_pthreads to using a vanilla event loop

For the last point, the original goal when designing the implementation
of pthreads into FRR was to be able to use the thread.c event based
system inside pthreads. This code essentially encapuslates all the
thread.c functionality into an easy to use pthread out of the box.
Creating a new frr_pthread with a null attributes field will cause the
created frr_pthread to run a thread.c event loop. The upshot of this is
that it is now possible to safely run existing functions in a pthread in
roughly 3 lines of code. It also serves as an example / starting point
for others.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>
This commit is contained in:
Quentin Young 2018-01-22 14:23:55 -05:00
parent 872c4e980e
commit a45dc9742c
No known key found for this signature in database
GPG Key ID: DAF48E0F57E0834F
2 changed files with 256 additions and 115 deletions
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229
lib/frr_pthread.c
View File

@ -1,5 +1,5 @@
/*
* Utilities and interfaces for managing POSIX threads
* Utilities and interfaces for managing POSIX threads within FRR.
* Copyright (C) 2017 Cumulus Networks
*
* This program is free software; you can redistribute it and/or modify
@ -25,79 +25,99 @@
#include "memory.h"
#include "hash.h"
DEFINE_MTYPE_STATIC(LIB, FRR_PTHREAD, "FRR POSIX Thread");
DEFINE_MTYPE(LIB, FRR_PTHREAD, "FRR POSIX Thread");
DEFINE_MTYPE(LIB, PTHREAD_PRIM, "POSIX synchronization primitives");
/* id for next created pthread */
static unsigned int next_id = 0;
/* Hash table of all frr_pthreads along with synchronization primitive(s) and
* hash table callbacks.
* ------------------------------------------------------------------------ */
static struct hash *pthread_table;
static pthread_mutex_t pthread_table_mtx = PTHREAD_MUTEX_INITIALIZER;
/* default frr_pthread start/stop routine prototypes */
static void *fpt_run(void *arg);
static int fpt_halt(struct frr_pthread *fpt, void **res);
/* pthread_table->hash_cmp */
static int pthread_table_hash_cmp(const void *value1, const void *value2)
/* default frr_pthread attributes */
struct frr_pthread_attr frr_pthread_attr_default = {
.id = 0,
.start = fpt_run,
.stop = fpt_halt,
.name = "Anonymous",
};
/* hash table to keep track of all frr_pthreads */
static struct hash *frr_pthread_hash;
static pthread_mutex_t frr_pthread_hash_mtx = PTHREAD_MUTEX_INITIALIZER;
/* frr_pthread_hash->hash_cmp */
static int frr_pthread_hash_cmp(const void *value1, const void *value2)
{
const struct frr_pthread *tq1 = value1;
const struct frr_pthread *tq2 = value2;
return (tq1->id == tq2->id);
return (tq1->attr.id == tq2->attr.id);
}
/* pthread_table->hash_key */
static unsigned int pthread_table_hash_key(void *value)
/* frr_pthread_hash->hash_key */
static unsigned int frr_pthread_hash_key(void *value)
{
return ((struct frr_pthread *)value)->id;
return ((struct frr_pthread *)value)->attr.id;
}
/* ------------------------------------------------------------------------ */
void frr_pthread_init()
{
pthread_mutex_lock(&pthread_table_mtx);
pthread_mutex_lock(&frr_pthread_hash_mtx);
{
pthread_table = hash_create(pthread_table_hash_key,
pthread_table_hash_cmp, NULL);
frr_pthread_hash = hash_create(frr_pthread_hash_key,
frr_pthread_hash_cmp, NULL);
}
pthread_mutex_unlock(&pthread_table_mtx);
pthread_mutex_unlock(&frr_pthread_hash_mtx);
}
void frr_pthread_finish()
{
pthread_mutex_lock(&pthread_table_mtx);
pthread_mutex_lock(&frr_pthread_hash_mtx);
{
hash_clean(pthread_table,
hash_clean(frr_pthread_hash,
(void (*)(void *))frr_pthread_destroy);
hash_free(pthread_table);
hash_free(frr_pthread_hash);
}
pthread_mutex_unlock(&pthread_table_mtx);
pthread_mutex_unlock(&frr_pthread_hash_mtx);
}
struct frr_pthread *frr_pthread_new(const char *name, unsigned int id,
void *(*start_routine)(void *),
int (*stop_routine)(void **,
struct frr_pthread *))
struct frr_pthread *frr_pthread_new(struct frr_pthread_attr *attr)
{
static struct frr_pthread holder = {0};
struct frr_pthread *fpt = NULL;
pthread_mutex_lock(&pthread_table_mtx);
attr = attr ? attr : &frr_pthread_attr_default;
pthread_mutex_lock(&frr_pthread_hash_mtx);
{
holder.id = id;
holder.attr.id = attr->id;
if (!hash_lookup(pthread_table, &holder)) {
struct frr_pthread *fpt = XCALLOC(
MTYPE_FRR_PTHREAD, sizeof(struct frr_pthread));
fpt->id = id;
fpt->master = thread_master_create(name);
fpt->start_routine = start_routine;
fpt->stop_routine = stop_routine;
fpt->name = XSTRDUP(MTYPE_FRR_PTHREAD, name);
if (!hash_lookup(frr_pthread_hash, &holder)) {
fpt = XCALLOC(MTYPE_FRR_PTHREAD,
sizeof(struct frr_pthread));
/* create new thread master */
fpt->master = thread_master_create(attr->name);
/* set attributes */
fpt->attr = *attr;
if (attr == &frr_pthread_attr_default)
fpt->attr.id = frr_pthread_get_id();
/* initialize startup synchronization primitives */
fpt->running_cond_mtx = XCALLOC(
MTYPE_PTHREAD_PRIM, sizeof(pthread_mutex_t));
fpt->running_cond = XCALLOC(MTYPE_PTHREAD_PRIM,
sizeof(pthread_cond_t));
pthread_mutex_init(fpt->running_cond_mtx, NULL);
pthread_cond_init(fpt->running_cond, NULL);
hash_get(pthread_table, fpt, hash_alloc_intern);
/* insert into global thread hash */
hash_get(frr_pthread_hash, fpt, hash_alloc_intern);
}
}
pthread_mutex_unlock(&pthread_table_mtx);
pthread_mutex_unlock(&frr_pthread_hash_mtx);
return fpt;
}
@ -105,7 +125,11 @@ struct frr_pthread *frr_pthread_new(const char *name, unsigned int id,
void frr_pthread_destroy(struct frr_pthread *fpt)
{
thread_master_free(fpt->master);
XFREE(MTYPE_FRR_PTHREAD, fpt->name);
pthread_mutex_destroy(fpt->running_cond_mtx);
pthread_cond_destroy(fpt->running_cond);
XFREE(MTYPE_PTHREAD_PRIM, fpt->running_cond_mtx);
XFREE(MTYPE_PTHREAD_PRIM, fpt->running_cond);
XFREE(MTYPE_FRR_PTHREAD, fpt);
}
@ -114,74 +138,82 @@ struct frr_pthread *frr_pthread_get(unsigned int id)
static struct frr_pthread holder = {0};
struct frr_pthread *fpt;
pthread_mutex_lock(&pthread_table_mtx);
pthread_mutex_lock(&frr_pthread_hash_mtx);
{
holder.id = id;
fpt = hash_lookup(pthread_table, &holder);
holder.attr.id = id;
fpt = hash_lookup(frr_pthread_hash, &holder);
}
pthread_mutex_unlock(&pthread_table_mtx);
pthread_mutex_unlock(&frr_pthread_hash_mtx);
return fpt;
}
int frr_pthread_run(unsigned int id, const pthread_attr_t *attr, void *arg)
int frr_pthread_run(struct frr_pthread *fpt, const pthread_attr_t *attr)
{
struct frr_pthread *fpt = frr_pthread_get(id);
int ret;
if (!fpt)
return -1;
ret = pthread_create(&fpt->thread, attr, fpt->attr.start, fpt);
ret = pthread_create(&fpt->thread, attr, fpt->start_routine, arg);
/* Per pthread_create(3), the contents of fpt->thread are undefined if
* pthread_create() did not succeed. Reset this value to zero. */
/*
* Per pthread_create(3), the contents of fpt->thread are undefined if
* pthread_create() did not succeed. Reset this value to zero.
*/
if (ret < 0)
memset(&fpt->thread, 0x00, sizeof(fpt->thread));
return ret;
}
/**
* Calls the stop routine for the frr_pthread and resets any relevant fields.
*
* @param fpt - the frr_pthread to stop
* @param result - pointer to result pointer
* @return the return code from the stop routine
*/
static int frr_pthread_stop_actual(struct frr_pthread *fpt, void **result)
void frr_pthread_wait_running(struct frr_pthread *fpt)
{
int ret = (*fpt->stop_routine)(result, fpt);
pthread_mutex_lock(fpt->running_cond_mtx);
{
while (!fpt->running)
pthread_cond_wait(fpt->running_cond,
fpt->running_cond_mtx);
}
pthread_mutex_unlock(fpt->running_cond_mtx);
}
void frr_pthread_notify_running(struct frr_pthread *fpt)
{
pthread_mutex_lock(fpt->running_cond_mtx);
{
fpt->running = true;
pthread_cond_signal(fpt->running_cond);
}
pthread_mutex_unlock(fpt->running_cond_mtx);
}
int frr_pthread_stop(struct frr_pthread *fpt, void **result)
{
int ret = (*fpt->attr.stop)(fpt, result);
memset(&fpt->thread, 0x00, sizeof(fpt->thread));
return ret;
}
int frr_pthread_stop(unsigned int id, void **result)
{
struct frr_pthread *fpt = frr_pthread_get(id);
return frr_pthread_stop_actual(fpt, result);
}
/**
/*
* Callback for hash_iterate to stop all frr_pthread's.
*/
static void frr_pthread_stop_all_iter(struct hash_backet *hb, void *arg)
{
struct frr_pthread *fpt = hb->data;
frr_pthread_stop_actual(fpt, NULL);
frr_pthread_stop(fpt, NULL);
}
void frr_pthread_stop_all()
{
pthread_mutex_lock(&pthread_table_mtx);
pthread_mutex_lock(&frr_pthread_hash_mtx);
{
hash_iterate(pthread_table, frr_pthread_stop_all_iter, NULL);
hash_iterate(frr_pthread_hash, frr_pthread_stop_all_iter, NULL);
}
pthread_mutex_unlock(&pthread_table_mtx);
pthread_mutex_unlock(&frr_pthread_hash_mtx);
}
unsigned int frr_pthread_get_id()
{
/* just a sanity check, this should never happen */
assert(next_id <= INT_MAX - 1);
return next_id++;
}
@ -189,3 +221,60 @@ void frr_pthread_yield(void)
{
(void)sched_yield();
}
/*
* ----------------------------------------------------------------------------
* Default Event Loop
* ----------------------------------------------------------------------------
*/
/* dummy task for sleeper pipe */
static int fpt_dummy(struct thread *thread)
{
return 0;
}
/* poison pill task to end event loop */
static int fpt_finish(struct thread *thread)
{
struct frr_pthread *fpt = THREAD_ARG(thread);
atomic_store_explicit(&fpt->running, false, memory_order_relaxed);
return 0;
}
/* stop function, called from other threads to halt this one */
static int fpt_halt(struct frr_pthread *fpt, void **res)
{
thread_add_event(fpt->master, &fpt_finish, fpt, 0, NULL);
pthread_join(fpt->thread, res);
fpt = NULL;
return 0;
}
/* entry pthread function & main event loop */
static void *fpt_run(void *arg)
{
struct frr_pthread *fpt = arg;
fpt->master->owner = pthread_self();
int sleeper[2];
pipe(sleeper);
thread_add_read(fpt->master, &fpt_dummy, NULL, sleeper[0], NULL);
fpt->master->handle_signals = false;
frr_pthread_notify_running(fpt);
struct thread task;
while (atomic_load_explicit(&fpt->running, memory_order_relaxed)) {
if (thread_fetch(fpt->master, &task)) {
thread_call(&task);
}
}
close(sleeper[1]);
close(sleeper[0]);
return NULL;
}

142
lib/frr_pthread.h
View File

@ -1,5 +1,5 @@
/*
* Utilities and interfaces for managing POSIX threads
* Utilities and interfaces for managing POSIX threads within FRR.
* Copyright (C) 2017 Cumulus Networks
*
* This program is free software; you can redistribute it and/or modify
@ -21,39 +21,73 @@
#define _FRR_PTHREAD_H
#include <pthread.h>
#include "frratomic.h"
#include "memory.h"
#include "thread.h"
DECLARE_MTYPE(FRR_PTHREAD);
DECLARE_MTYPE(PTHREAD_PRIM);
struct frr_pthread;
struct frr_pthread_attr;
struct frr_pthread_attr {
int id;
void *(*start)(void *);
int (*stop)(struct frr_pthread *, void **);
const char *name;
};
struct frr_pthread {
/* pthread id */
pthread_t thread;
/* frr thread identifier */
unsigned int id;
/* thread master for this pthread's thread.c event loop */
struct thread_master *master;
/* start routine */
void *(*start_routine)(void *);
/* caller-specified data; start & stop funcs, name, id */
struct frr_pthread_attr attr;
/* stop routine */
int (*stop_routine)(void **, struct frr_pthread *);
/*
* Notification mechanism for allowing pthreads to notify their parents
* when they are ready to do work. This mechanism has two associated
* functions:
*
* - frr_pthread_wait_running()
* This function should be called by the spawning thread after
* frr_pthread_run(). It safely waits until the spawned thread
* indicates that is ready to do work by posting to the condition
* variable.
*
* - frr_pthread_notify_running()
* This function should be called by the spawned thread when it is
* ready to do work. It will wake up any threads waiting on the
* previously described condition.
*/
pthread_cond_t *running_cond;
pthread_mutex_t *running_cond_mtx;
_Atomic bool running;
/* the (hopefully descriptive) name of this thread */
char *name;
/*
* Fake thread-specific storage. No constraints on usage. Helpful when
* creating reentrant pthread implementations. Can be used to pass
* argument to pthread entry function.
*/
void *data;
};
/* Initializes this module.
extern struct frr_pthread_attr frr_pthread_attr_default;
/*
* Initializes this module.
*
* Must be called before using any of the other functions.
*/
void frr_pthread_init(void);
/* Uninitializes this module.
/*
* Uninitializes this module.
*
* Destroys all registered frr_pthread's and internal data structures.
*
@ -62,34 +96,23 @@ void frr_pthread_init(void);
*/
void frr_pthread_finish(void);
/* Creates a new frr_pthread.
/*
* Creates a new frr_pthread with the given attributes.
*
* If the provided ID is already assigned to an existing frr_pthread, the
* return value will be NULL.
*
* @param name - the name of the thread. Doesn't have to be unique, but it
* probably should be. This value is copied and may be safely free'd upon
* return.
*
* @param id - the integral ID of the thread. MUST be unique. The caller may
* use this id to retrieve the thread.
*
* @param start_routine - start routine for the pthread, will be passed to
* pthread_create (see those docs for details)
*
* @param stop_routine - stop routine for the pthread, called to terminate the
* thread. This function should gracefully stop the pthread and clean up any
* thread-specific resources. The passed pointer is used to return a data
* result.
* The 'attr' argument should be filled out with the desired attributes,
* including ID, start and stop functions and the desired name. Alternatively,
* if attr is NULL, the default attributes will be used. The pthread will be
* set up to run a basic threadmaster loop and the name will be "Anonymous".
* Scheduling tasks onto the threadmaster in the 'master' field of the returned
* frr_pthread will cause them to run on that pthread.
*
* @param attr - the thread attributes
* @return the created frr_pthread upon success, or NULL upon failure
*/
struct frr_pthread *frr_pthread_new(const char *name, unsigned int id,
void *(*start_routine)(void *),
int (*stop_routine)(void **,
struct frr_pthread *));
struct frr_pthread *frr_pthread_new(struct frr_pthread_attr *attr);
/* Destroys an frr_pthread.
/*
* Destroys an frr_pthread.
*
* Assumes that the associated pthread, if any, has already terminated.
*
@ -97,38 +120,66 @@ struct frr_pthread *frr_pthread_new(const char *name, unsigned int id,
*/
void frr_pthread_destroy(struct frr_pthread *fpt);
/* Gets an existing frr_pthread by its id.
/*
* Gets an existing frr_pthread by its id.
*
* @return frr_thread associated with the provided id, or NULL on error
*/
struct frr_pthread *frr_pthread_get(unsigned int id);
/* Creates a new pthread and binds it to a frr_pthread.
/*
* Creates a new pthread and binds it to a frr_pthread.
*
* This function is a wrapper for pthread_create. The first parameter is the
* frr_pthread to bind the created pthread to. All subsequent arguments are
* passed unmodified to pthread_create().
* passed unmodified to pthread_create(). The frr_pthread * provided will be
* used as the argument to the pthread entry function. If it is necessary to
* pass additional data, the 'data' field in the frr_pthread may be used.
*
* This function returns the same code as pthread_create(). If the value is
* zero, the provided frr_pthread is bound to a running POSIX thread. If the
* value is less than zero, the provided frr_pthread is guaranteed to be a
* clean instance that may be susbsequently passed to frr_pthread_run().
*
* @param id - frr_pthread to bind the created pthread to
* @param fpt - frr_pthread * to run
* @param attr - see pthread_create(3)
* @param arg - see pthread_create(3)
*
* @return see pthread_create(3)
*/
int frr_pthread_run(unsigned int id, const pthread_attr_t *attr, void *arg);
int frr_pthread_run(struct frr_pthread *fpt, const pthread_attr_t *attr);
/* Stops an frr_pthread with a result.
/*
* Waits until the specified pthread has finished setting up and is ready to
* begin work.
*
* @param id - frr_pthread to stop
* If the pthread's code makes use of the startup synchronization mechanism,
* this function should be called before attempting to use the functionality
* exposed by the pthread. It waits until the 'running' condition is satisfied
* (see struct definition of frr_pthread).
*
* @param fpt - the frr_pthread * to wait on
*/
void frr_pthread_wait_running(struct frr_pthread *fpt);
/*
* Notifies other pthreads that the calling thread has finished setting up and
* is ready to begin work.
*
* This will allow any other pthreads waiting in 'frr_pthread_wait_running' to
* proceed.
*
* @param fpt - the frr_pthread * that has finished setting up
*/
void frr_pthread_notify_running(struct frr_pthread *fpt);
/*
* Stops a frr_pthread with a result.
*
* @param fpt - frr_pthread * to stop
* @param result - where to store the thread's result, if any. May be NULL if a
* result is not needed.
*/
int frr_pthread_stop(unsigned int id, void **result);
int frr_pthread_stop(struct frr_pthread *fpt, void **result);
/* Stops all frr_pthread's. */
void frr_pthread_stop_all(void);
@ -136,7 +187,8 @@ void frr_pthread_stop_all(void);
/* Yields the current thread of execution */
void frr_pthread_yield(void);
/* Returns a unique identifier for use with frr_pthread_new().
/*
* Returns a unique identifier for use with frr_pthread_new().
*
* Internally, this is an integer that increments after each call to this
* function. Because the number of pthreads created should never exceed INT_MAX