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Diffstat (limited to '')
| -rw-r--r-- | mysys/wqueue.c | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/mysys/wqueue.c b/mysys/wqueue.c new file mode 100644 index 00000000..84fac01f --- /dev/null +++ b/mysys/wqueue.c @@ -0,0 +1,242 @@ +/* + Copyright (c) 2007, 2008, Sun Microsystems, Inc, + Copyright (c) 2011, 2012, Monty Program Ab + + 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; version 2 of the License. + + 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 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 Street, Fifth Floor, Boston, MA 02110-1335 USA */ + +#include <my_global.h> +#include <wqueue.h> + +#define STRUCT_PTR(TYPE, MEMBER, a) \ + (TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER)) +/* + Link a thread into double-linked queue of waiting threads. + + SYNOPSIS + wqueue_link_into_queue() + wqueue pointer to the queue structure + thread pointer to the thread to be added to the queue + + RETURN VALUE + none + + NOTES. + Queue is represented by a circular list of the thread structures + The list is double-linked of the type (**prev,*next), accessed by + a pointer to the last element. +*/ + +void wqueue_link_into_queue(WQUEUE *wqueue, struct st_my_thread_var *thread) +{ + struct st_my_thread_var *last; + if (!(last= wqueue->last_thread)) + { + /* Queue is empty */ + thread->next= thread; + thread->prev= &thread->next; + } + else + { + thread->prev= last->next->prev; + last->next->prev= &thread->next; + thread->next= last->next; + last->next= thread; + } + wqueue->last_thread= thread; +} + + +/* + Add a thread to single-linked queue of waiting threads + + SYNOPSIS + wqueue_add_to_queue() + wqueue pointer to the queue structure + thread pointer to the thread to be added to the queue + + RETURN VALUE + none + + NOTES. + Queue is represented by a circular list of the thread structures + The list is single-linked of the type (*next), accessed by a pointer + to the last element. +*/ + +void wqueue_add_to_queue(WQUEUE *wqueue, struct st_my_thread_var *thread) +{ + struct st_my_thread_var *last; + if (!(last= wqueue->last_thread)) + thread->next= thread; + else + { + thread->next= last->next; + last->next= thread; + } +#ifndef DBUG_OFF + thread->prev= NULL; /* force segfault if used */ +#endif + wqueue->last_thread= thread; +} + +/* + Unlink a thread from double-linked queue of waiting threads + + SYNOPSIS + wqueue_unlink_from_queue() + wqueue pointer to the queue structure + thread pointer to the thread to be removed from the queue + + RETURN VALUE + none + + NOTES. + See NOTES for link_into_queue +*/ + +void wqueue_unlink_from_queue(WQUEUE *wqueue, struct st_my_thread_var *thread) +{ + if (thread->next == thread) + /* The queue contains only one member */ + wqueue->last_thread= NULL; + else + { + thread->next->prev= thread->prev; + *thread->prev= thread->next; + if (wqueue->last_thread == thread) + wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next, + thread->prev); + } + thread->next= NULL; +} + + +/* + Remove all threads from queue signaling them to proceed + + SYNOPSIS + wqueue_realease_queue() + wqueue pointer to the queue structure + thread pointer to the thread to be added to the queue + + RETURN VALUE + none + + NOTES. + See notes for add_to_queue + When removed from the queue each thread is signaled via condition + variable thread->suspend. +*/ + +void wqueue_release_queue(WQUEUE *wqueue) +{ + struct st_my_thread_var *last= wqueue->last_thread; + struct st_my_thread_var *next= last->next; + struct st_my_thread_var *thread; + do + { + thread= next; + mysql_cond_signal(&thread->suspend); + next= thread->next; + thread->next= NULL; + } + while (thread != last); + wqueue->last_thread= NULL; +} + + +/** + @brief Removes all threads waiting for read or first one waiting for write. + + @param wqueue pointer to the queue structure + @param thread pointer to the thread to be added to the queue + + @note This function is applicable only to single linked lists. +*/ + +void wqueue_release_one_locktype_from_queue(WQUEUE *wqueue) +{ + struct st_my_thread_var *last= wqueue->last_thread; + struct st_my_thread_var *next= last->next; + struct st_my_thread_var *thread; + struct st_my_thread_var *new_list= NULL; + uint first_type= next->lock_type; + if (first_type == MY_PTHREAD_LOCK_WRITE) + { + /* release first waiting for write lock */ + mysql_cond_signal(&next->suspend); + if (next == last) + wqueue->last_thread= NULL; + else + last->next= next->next; + next->next= NULL; + return; + } + do + { + thread= next; + next= thread->next; + if (thread->lock_type == MY_PTHREAD_LOCK_WRITE) + { + /* skip waiting for write lock */ + if (new_list) + { + thread->next= new_list->next; + new_list= new_list->next= thread; + } + else + new_list= thread->next= thread; + } + else + { + /* release waiting for read lock */ + mysql_cond_signal(&thread->suspend); + thread->next= NULL; + } + } while (thread != last); + wqueue->last_thread= new_list; +} + + +/* + Add thread and wait + + SYNOPSIS + wqueue_add_and_wait() + wqueue queue to add to + thread thread which is waiting + lock mutex need for the operation +*/ + +void wqueue_add_and_wait(WQUEUE *wqueue, + struct st_my_thread_var *thread, + mysql_mutex_t *lock) +{ + DBUG_ENTER("wqueue_add_and_wait"); + DBUG_PRINT("enter", + ("thread: %p cond: %p mutex: %p", + thread, &thread->suspend, lock)); + wqueue_add_to_queue(wqueue, thread); + do + { + DBUG_PRINT("info", ("wait... cond: %p mutex: %p", + &thread->suspend, lock)); + mysql_cond_wait(&thread->suspend, lock); + DBUG_PRINT("info", ("wait done cond: %p mutex: %p next: %p", + &thread->suspend, lock, + thread->next)); + } + while (thread->next); + DBUG_VOID_RETURN; +} |