From 44a3eaeba04ef78835ca741592c376428ada5f71 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Sat, 2 Dec 2017 10:30:25 +0100 Subject: New upstream version 0.9.8 --- lib/glthread/lock.c | 186 ++++++++++++++++++++++++++++++++++++++++++++--- lib/glthread/lock.h | 66 +++++++++++++++-- lib/glthread/threadlib.c | 4 +- 3 files changed, 236 insertions(+), 20 deletions(-) (limited to 'lib/glthread') diff --git a/lib/glthread/lock.c b/lib/glthread/lock.c index 459955dd..df05dbc0 100644 --- a/lib/glthread/lock.c +++ b/lib/glthread/lock.c @@ -1,5 +1,5 @@ /* Locking in multithreaded situations. - Copyright (C) 2005-2016 Free Software Foundation, Inc. + Copyright (C) 2005-2017 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of either: @@ -21,7 +21,7 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License - along with this program; if not, see . */ + along with this program; if not, see . */ /* Written by Bruno Haible , 2005. Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h, @@ -39,9 +39,38 @@ /* ------------------------- gl_rwlock_t datatype ------------------------- */ -# if HAVE_PTHREAD_RWLOCK +# if HAVE_PTHREAD_RWLOCK && (HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER || (defined PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP && (__GNU_LIBRARY__ > 1))) -# if !defined PTHREAD_RWLOCK_INITIALIZER +# ifdef PTHREAD_RWLOCK_INITIALIZER + +# if !HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER + /* glibc with bug https://sourceware.org/bugzilla/show_bug.cgi?id=13701 */ + +int +glthread_rwlock_init_for_glibc (pthread_rwlock_t *lock) +{ + pthread_rwlockattr_t attributes; + int err; + + err = pthread_rwlockattr_init (&attributes); + if (err != 0) + return err; + /* Note: PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP is the only value that + causes the writer to be preferred. PTHREAD_RWLOCK_PREFER_WRITER_NP does not + do this; see + http://man7.org/linux/man-pages/man3/pthread_rwlockattr_setkind_np.3.html */ + err = pthread_rwlockattr_setkind_np (&attributes, + PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP); + if (err == 0) + err = pthread_rwlock_init(lock, &attributes); + /* pthread_rwlockattr_destroy always returns 0. It cannot influence the + return value. */ + pthread_rwlockattr_destroy (&attributes); + return err; +} + +# endif +# else int glthread_rwlock_init_multithreaded (gl_rwlock_t *lock) @@ -161,11 +190,9 @@ glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock) if (err != 0) return err; /* Test whether only readers are currently running, and whether the runcount - field will not overflow. */ - /* POSIX says: "It is implementation-defined whether the calling thread - acquires the lock when a writer does not hold the lock and there are - writers blocked on the lock." Let's say, no: give the writers a higher - priority. */ + field will not overflow, and whether no writer is waiting. The latter + condition is because POSIX recommends that "write locks shall take + precedence over read locks", to avoid "writer starvation". */ while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0)) { /* This thread has to wait for a while. Enqueue it among the @@ -490,6 +517,141 @@ glthread_once_singlethreaded (pthread_once_t *once_control) /* ------------------------- gl_rwlock_t datatype ------------------------- */ +# if !HAVE_PTH_RWLOCK_ACQUIRE_PREFER_WRITER + +int +glthread_rwlock_init_multithreaded (gl_rwlock_t *lock) +{ + if (!pth_mutex_init (&lock->lock)) + return errno; + if (!pth_cond_init (&lock->waiting_readers)) + return errno; + if (!pth_cond_init (&lock->waiting_writers)) + return errno; + lock->waiting_writers_count = 0; + lock->runcount = 0; + lock->initialized = 1; + return 0; +} + +int +glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock) +{ + if (!lock->initialized) + glthread_rwlock_init_multithreaded (lock); + if (!pth_mutex_acquire (&lock->lock, 0, NULL)) + return errno; + /* Test whether only readers are currently running, and whether the runcount + field will not overflow, and whether no writer is waiting. The latter + condition is because POSIX recommends that "write locks shall take + precedence over read locks", to avoid "writer starvation". */ + while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0)) + { + /* This thread has to wait for a while. Enqueue it among the + waiting_readers. */ + if (!pth_cond_await (&lock->waiting_readers, &lock->lock, NULL)) + { + int err = errno; + pth_mutex_release (&lock->lock); + return err; + } + } + lock->runcount++; + return (!pth_mutex_release (&lock->lock) ? errno : 0); +} + +int +glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock) +{ + if (!lock->initialized) + glthread_rwlock_init_multithreaded (lock); + if (!pth_mutex_acquire (&lock->lock, 0, NULL)) + return errno; + /* Test whether no readers or writers are currently running. */ + while (!(lock->runcount == 0)) + { + /* This thread has to wait for a while. Enqueue it among the + waiting_writers. */ + lock->waiting_writers_count++; + if (!pth_cond_await (&lock->waiting_writers, &lock->lock, NULL)) + { + int err = errno; + lock->waiting_writers_count--; + pth_mutex_release (&lock->lock); + return err; + } + lock->waiting_writers_count--; + } + lock->runcount--; /* runcount becomes -1 */ + return (!pth_mutex_release (&lock->lock) ? errno : 0); +} + +int +glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock) +{ + int err; + + if (!lock->initialized) + return EINVAL; + if (!pth_mutex_acquire (&lock->lock, 0, NULL)) + return errno; + if (lock->runcount < 0) + { + /* Drop a writer lock. */ + if (!(lock->runcount == -1)) + { + pth_mutex_release (&lock->lock); + return EINVAL; + } + lock->runcount = 0; + } + else + { + /* Drop a reader lock. */ + if (!(lock->runcount > 0)) + { + pth_mutex_release (&lock->lock); + return EINVAL; + } + lock->runcount--; + } + if (lock->runcount == 0) + { + /* POSIX recommends that "write locks shall take precedence over read + locks", to avoid "writer starvation". */ + if (lock->waiting_writers_count > 0) + { + /* Wake up one of the waiting writers. */ + if (!pth_cond_notify (&lock->waiting_writers, FALSE)) + { + int err = errno; + pth_mutex_release (&lock->lock); + return err; + } + } + else + { + /* Wake up all waiting readers. */ + if (!pth_cond_notify (&lock->waiting_readers, TRUE)) + { + int err = errno; + pth_mutex_release (&lock->lock); + return err; + } + } + } + return (!pth_mutex_release (&lock->lock) ? errno : 0); +} + +int +glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock) +{ + lock->initialized = 0; + return 0; +} + +# endif + /* --------------------- gl_recursive_lock_t datatype --------------------- */ /* -------------------------- gl_once_t datatype -------------------------- */ @@ -805,8 +967,10 @@ glthread_rwlock_rdlock_func (gl_rwlock_t *lock) } EnterCriticalSection (&lock->lock); /* Test whether only readers are currently running, and whether the runcount - field will not overflow. */ - if (!(lock->runcount + 1 > 0)) + field will not overflow, and whether no writer is waiting. The latter + condition is because POSIX recommends that "write locks shall take + precedence over read locks", to avoid "writer starvation". */ + if (!(lock->runcount + 1 > 0 && lock->waiting_writers.count == 0)) { /* This thread has to wait for a while. Enqueue it among the waiting_readers. */ diff --git a/lib/glthread/lock.h b/lib/glthread/lock.h index 2e001689..06285558 100644 --- a/lib/glthread/lock.h +++ b/lib/glthread/lock.h @@ -1,5 +1,5 @@ /* Locking in multithreaded situations. - Copyright (C) 2005-2016 Free Software Foundation, Inc. + Copyright (C) 2005-2017 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of either: @@ -21,7 +21,7 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License - along with this program; if not, see . */ + along with this program; if not, see . */ /* Written by Bruno Haible , 2005. Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h, @@ -148,6 +148,11 @@ extern int glthread_in_use (void); # pragma weak pthread_mutexattr_init # pragma weak pthread_mutexattr_settype # pragma weak pthread_mutexattr_destroy +# pragma weak pthread_rwlockattr_init +# if __GNU_LIBRARY__ > 1 +# pragma weak pthread_rwlockattr_setkind_np +# endif +# pragma weak pthread_rwlockattr_destroy # ifndef pthread_self # pragma weak pthread_self # endif @@ -185,7 +190,7 @@ typedef pthread_mutex_t gl_lock_t; /* ------------------------- gl_rwlock_t datatype ------------------------- */ -# if HAVE_PTHREAD_RWLOCK +# if HAVE_PTHREAD_RWLOCK && (HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER || (defined PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP && (__GNU_LIBRARY__ > 1))) # ifdef PTHREAD_RWLOCK_INITIALIZER @@ -194,10 +199,18 @@ typedef pthread_rwlock_t gl_rwlock_t; STORAGECLASS pthread_rwlock_t NAME; # define gl_rwlock_define_initialized(STORAGECLASS, NAME) \ STORAGECLASS pthread_rwlock_t NAME = gl_rwlock_initializer; -# define gl_rwlock_initializer \ - PTHREAD_RWLOCK_INITIALIZER -# define glthread_rwlock_init(LOCK) \ - (pthread_in_use () ? pthread_rwlock_init (LOCK, NULL) : 0) +# if HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER +# define gl_rwlock_initializer \ + PTHREAD_RWLOCK_INITIALIZER +# define glthread_rwlock_init(LOCK) \ + (pthread_in_use () ? pthread_rwlock_init (LOCK, NULL) : 0) +# else /* glibc with bug https://sourceware.org/bugzilla/show_bug.cgi?id=13701 */ +# define gl_rwlock_initializer \ + PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP +# define glthread_rwlock_init(LOCK) \ + (pthread_in_use () ? glthread_rwlock_init_for_glibc (LOCK) : 0) +extern int glthread_rwlock_init_for_glibc (pthread_rwlock_t *lock); +# endif # define glthread_rwlock_rdlock(LOCK) \ (pthread_in_use () ? pthread_rwlock_rdlock (LOCK) : 0) # define glthread_rwlock_wrlock(LOCK) \ @@ -436,6 +449,9 @@ typedef pth_mutex_t gl_lock_t; /* ------------------------- gl_rwlock_t datatype ------------------------- */ +/* Pth pth_rwlock_acquire always prefers readers. No autoconf test so far. */ +# if HAVE_PTH_RWLOCK_ACQUIRE_PREFER_WRITER + typedef pth_rwlock_t gl_rwlock_t; # define gl_rwlock_define(STORAGECLASS, NAME) \ STORAGECLASS pth_rwlock_t NAME; @@ -454,6 +470,42 @@ typedef pth_rwlock_t gl_rwlock_t; # define glthread_rwlock_destroy(LOCK) \ ((void)(LOCK), 0) +# else + +typedef struct + { + int initialized; + pth_mutex_t lock; /* protects the remaining fields */ + pth_cond_t waiting_readers; /* waiting readers */ + pth_cond_t waiting_writers; /* waiting writers */ + unsigned int waiting_writers_count; /* number of waiting writers */ + int runcount; /* number of readers running, or -1 when a writer runs */ + } + gl_rwlock_t; +# define gl_rwlock_define(STORAGECLASS, NAME) \ + STORAGECLASS gl_rwlock_t NAME; +# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \ + STORAGECLASS gl_rwlock_t NAME = gl_rwlock_initializer; +# define gl_rwlock_initializer \ + { 0 } +# define glthread_rwlock_init(LOCK) \ + (pth_in_use () ? glthread_rwlock_init_multithreaded (LOCK) : 0) +# define glthread_rwlock_rdlock(LOCK) \ + (pth_in_use () ? glthread_rwlock_rdlock_multithreaded (LOCK) : 0) +# define glthread_rwlock_wrlock(LOCK) \ + (pth_in_use () ? glthread_rwlock_wrlock_multithreaded (LOCK) : 0) +# define glthread_rwlock_unlock(LOCK) \ + (pth_in_use () ? glthread_rwlock_unlock_multithreaded (LOCK) : 0) +# define glthread_rwlock_destroy(LOCK) \ + (pth_in_use () ? glthread_rwlock_destroy_multithreaded (LOCK) : 0) +extern int glthread_rwlock_init_multithreaded (gl_rwlock_t *lock); +extern int glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock); +extern int glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock); +extern int glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock); +extern int glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock); + +# endif + /* --------------------- gl_recursive_lock_t datatype --------------------- */ /* In Pth, mutexes are recursive by default. */ diff --git a/lib/glthread/threadlib.c b/lib/glthread/threadlib.c index 70d4eef4..82b8861b 100644 --- a/lib/glthread/threadlib.c +++ b/lib/glthread/threadlib.c @@ -1,5 +1,5 @@ /* Multithreading primitives. - Copyright (C) 2005-2016 Free Software Foundation, Inc. + Copyright (C) 2005-2017 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of either: @@ -21,7 +21,7 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License - along with this program; if not, see . */ + along with this program; if not, see . */ /* Written by Bruno Haible , 2005. */ -- cgit v1.2.3