thr_cond.h

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#ifndef THR_COND_INCLUDED
#define THR_COND_INCLUDED
 
/* Copyright (c) 2014, 2025, Oracle and/or its affiliates.
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have either included with
   the program or referenced in the documentation.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
/**
  @file include/thr_cond.h
  MySQL condition variable implementation.
 
  There are three "layers":
  1) native_cond_*()
       Functions that map directly down to OS primitives.
       Windows    - ConditionVariable
       Other OSes - pthread
  2) my_cond_*()
       Functions that use SAFE_MUTEX (default for debug).
       Otherwise native_cond_*() is used.
  3) mysql_cond*()
       Functions that include Performance Schema instrumentation.
       See include/mysql/psi/mysql_thread.h
*/
 
#include <sys/types.h>
#ifdef _WIN32
#include <time.h>
#include "my_inttypes.h"
#include "my_systime.h"
#endif
 
#include "mysql/components/services/bits/thr_cond_bits.h"
#include "mysql/components/services/bits/thr_mutex_bits.h"
 
#ifdef _WIN32
/**
  Convert abstime to milliseconds
*/
 
static DWORD get_milliseconds(const struct timespec *abstime) {
  /*
    Convert timespec to millis and subtract current time.
    my_getsystime() returns time in 100 ns units.
  */
  const ulonglong future = abstime->tv_sec * 1000 + abstime->tv_nsec / 1000000;
  const ulonglong now = my_getsystime() / 10000;
  /* Don't allow the timeout to be negative. */
  if (future < now) return 0;
  return (DWORD)(future - now);
}
#endif /* _WIN32 */
 
static inline int native_cond_init(native_cond_t *cond) {
#ifdef _WIN32
  InitializeConditionVariable(cond);
  return 0;
#else
  /* pthread_condattr_t is not used in MySQL */
  return pthread_cond_init(cond, nullptr);
#endif
}
 
static inline int native_cond_destroy(native_cond_t *cond [[maybe_unused]]) {
#ifdef _WIN32
  return 0; /* no destroy function */
#else
  return pthread_cond_destroy(cond);
#endif
}
 
static inline int native_cond_timedwait(native_cond_t *cond,
                                        native_mutex_t *mutex,
                                        const struct timespec *abstime) {
#ifdef _WIN32
  const DWORD timeout = get_milliseconds(abstime);
  if (!SleepConditionVariableCS(cond, mutex, timeout)) return ETIMEDOUT;
  return 0;
#else
  return pthread_cond_timedwait(cond, mutex, abstime);
#endif
}
 
static inline int native_cond_wait(native_cond_t *cond, native_mutex_t *mutex) {
#ifdef _WIN32
  if (!SleepConditionVariableCS(cond, mutex, INFINITE)) return ETIMEDOUT;
  return 0;
#else
  return pthread_cond_wait(cond, mutex);
#endif
}
 
static inline int native_cond_signal(native_cond_t *cond) {
#ifdef _WIN32
  WakeConditionVariable(cond);
  return 0;
#else
  return pthread_cond_signal(cond);
#endif
}
 
static inline int native_cond_broadcast(native_cond_t *cond) {
#ifdef _WIN32
  WakeAllConditionVariable(cond);
  return 0;
#else
  return pthread_cond_broadcast(cond);
#endif
}
 
#ifdef SAFE_MUTEX
struct safe_mutex_t;
int safe_cond_wait(native_cond_t *cond, safe_mutex_t *mp, const char *file,
                   uint line);
int safe_cond_timedwait(native_cond_t *cond, safe_mutex_t *mp,
                        const struct timespec *abstime, const char *file,
                        uint line);
#endif
 
static inline int my_cond_timedwait(native_cond_t *cond, my_mutex_t *mp,
                                    const struct timespec *abstime
#ifdef SAFE_MUTEX
                                    ,
                                    const char *file, uint line
#endif
) {
#ifdef SAFE_MUTEX
  return safe_cond_timedwait(cond, mp->m_u.m_safe_ptr, abstime, file, line);
#else
  return native_cond_timedwait(cond, &mp->m_u.m_native, abstime);
#endif
}
 
static inline int my_cond_wait(native_cond_t *cond, my_mutex_t *mp
#ifdef SAFE_MUTEX
                               ,
                               const char *file, uint line
#endif
) {
#ifdef SAFE_MUTEX
  return safe_cond_wait(cond, mp->m_u.m_safe_ptr, file, line);
#else
  return native_cond_wait(cond, &mp->m_u.m_native);
#endif
}
 
#endif /* THR_COND_INCLUDED */