blob: 39ff7e8288db241da85c6e10c22e56b338007b49 [file] [log] [blame]
/*
* functions about threads.
*
* Copyright (C) 2017 Christopher Fauet - cfaulet@haproxy.com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <common/cfgparse.h>
#include <common/hathreads.h>
#include <common/standard.h>
#include <types/global.h>
#include <proto/fd.h>
#ifdef USE_THREAD
volatile unsigned long threads_want_rdv_mask = 0;
volatile unsigned long threads_harmless_mask = 0;
volatile unsigned long all_threads_mask = 1; // nbthread 1 assumed by default
THREAD_LOCAL unsigned int tid = 0;
THREAD_LOCAL unsigned long tid_bit = (1UL << 0);
#if defined(DEBUG_THREAD) || defined(DEBUG_FULL)
struct lock_stat lock_stats[LOCK_LABELS];
#endif
/* Marks the thread as harmless until the last thread using the rendez-vous
* point quits. Given that we can wait for a long time, sched_yield() is used
* when available to offer the CPU resources to competing threads if needed.
*/
void thread_harmless_till_end()
{
HA_ATOMIC_OR(&threads_harmless_mask, tid_bit);
while (threads_want_rdv_mask & all_threads_mask) {
#if _POSIX_PRIORITY_SCHEDULING
sched_yield();
#else
pl_cpu_relax();
#endif
}
}
/* Isolates the current thread : request the ability to work while all other
* threads are harmless. Only returns once all of them are harmless, with the
* current thread's bit in threads_harmless_mask cleared. Needs to be completed
* using thread_release().
*/
void thread_isolate()
{
unsigned long old;
HA_ATOMIC_OR(&threads_harmless_mask, tid_bit);
__ha_barrier_store();
HA_ATOMIC_OR(&threads_want_rdv_mask, tid_bit);
/* wait for all threads to become harmless */
old = threads_harmless_mask;
while (1) {
if (unlikely((old & all_threads_mask) != all_threads_mask))
old = threads_harmless_mask;
else if (HA_ATOMIC_CAS(&threads_harmless_mask, &old, old & ~tid_bit))
break;
#if _POSIX_PRIORITY_SCHEDULING
sched_yield();
#else
pl_cpu_relax();
#endif
}
/* one thread gets released at a time here, with its harmess bit off.
* The loss of this bit makes the other one continue to spin while the
* thread is working alone.
*/
}
/* Cancels the effect of thread_isolate() by releasing the current thread's bit
* in threads_want_rdv_mask and by marking this thread as harmless until the
* last worker finishes.
*/
void thread_release()
{
HA_ATOMIC_AND(&threads_want_rdv_mask, ~tid_bit);
thread_harmless_end();
}
/* these calls are used as callbacks at init time */
void ha_spin_init(HA_SPINLOCK_T *l)
{
HA_SPIN_INIT(l);
}
/* these calls are used as callbacks at init time */
void ha_rwlock_init(HA_RWLOCK_T *l)
{
HA_RWLOCK_INIT(l);
}
__attribute__((constructor))
static void __hathreads_init(void)
{
#if defined(DEBUG_THREAD) || defined(DEBUG_FULL)
memset(lock_stats, 0, sizeof(lock_stats));
#endif
}
REGISTER_BUILD_OPTS("Built with multi-threading support.");
#else
REGISTER_BUILD_OPTS("Built without multi-threading support (USE_THREAD not set).");
#endif // USE_THREAD
/* Parse the number of threads in argument <arg>, returns it and adjusts a few
* internal variables accordingly, or fails and returns zero with an error
* reason in <errmsg>. May be called multiple times while parsing.
*/
int parse_nbthread(const char *arg, char **err)
{
long nbthread;
char *errptr;
nbthread = strtol(arg, &errptr, 10);
if (!*arg || *errptr) {
memprintf(err, "passed a missing or unparsable integer value in '%s'", arg);
return 0;
}
#ifndef USE_THREAD
if (nbthread != 1) {
memprintf(err, "specified with a value other than 1 while HAProxy is not compiled with threads support. Please check build options for USE_THREAD");
return 0;
}
#else
if (nbthread < 1 || nbthread > MAX_THREADS) {
memprintf(err, "value must be between 1 and %d (was %ld)", MAX_THREADS, nbthread);
return 0;
}
/* we proceed like this to be sure never to overflow the left shift */
all_threads_mask = 1UL << (nbthread - 1);
all_threads_mask |= all_threads_mask - 1;
#endif
return nbthread;
}