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* The rw_lock is now using a mutex to protect its reader/writer counts. This

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makes the reader case a lot less expensive, and should relieve the thread
  spinlock contention a bit.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33643 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2009-10-18 19:52:09 +00:00
parent b2a7fcb404
commit 22ea088498
2 changed files with 23 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
headers/private/kernel/lock.h
View File

@ -42,6 +42,7 @@ struct rw_lock_waiter;
typedef struct rw_lock {
const char* name;
mutex lock;
struct rw_lock_waiter* waiters;
thread_id holder;
int32 reader_count;
@ -85,7 +86,8 @@ typedef struct rw_lock {
# define RECURSIVE_LOCK_INITIALIZER(name) { MUTEX_INITIALIZER(name), -1, 0 }
#endif
#define RW_LOCK_INITIALIZER(name) { name, NULL, -1, 0, 0, 0 }
#define RW_LOCK_INITIALIZER(name) { name, MUTEX_INITIALIZER(name), \
NULL, -1, 0, 0, 0 }
#if KDEBUG

26
src/system/kernel/lock.cpp
View File

@ -164,6 +164,10 @@ rw_lock_wait(rw_lock* lock, bool writer)
lock->waiters->last = &waiter;
InterruptsSpinLocker locker(gThreadSpinlock);
_mutex_unlock(&lock->lock, true);
// block
thread_prepare_to_block(waiter.thread, 0, THREAD_BLOCK_TYPE_RW_LOCK, lock);
return thread_block_locked(waiter.thread);
@ -190,6 +194,7 @@ rw_lock_unblock(rw_lock* lock)
lock->holder = waiter->thread->id;
// unblock thread
InterruptsSpinLocker locker(gThreadSpinlock);
thread_unblock_locked(waiter->thread, B_OK);
}
return;
@ -205,6 +210,7 @@ rw_lock_unblock(rw_lock* lock)
lock->reader_count++;
// unblock thread
InterruptsSpinLocker locker(gThreadSpinlock);
thread_unblock_locked(waiter->thread, B_OK);
}
}
@ -221,6 +227,8 @@ rw_lock_init(rw_lock* lock, const char* name)
lock->owner_count = 0;
lock->flags = 0;
mutex_init(&lock->lock, name);
T_SCHEDULING_ANALYSIS(InitRWLock(lock, name));
NotifyWaitObjectListeners(&WaitObjectListener::RWLockInitialized, lock);
}
@ -237,6 +245,8 @@ rw_lock_init_etc(rw_lock* lock, const char* name, uint32 flags)
lock->owner_count = 0;
lock->flags = flags & RW_LOCK_FLAG_CLONE_NAME;
mutex_init(&lock->lock, lock->name);
T_SCHEDULING_ANALYSIS(InitRWLock(lock, name));
NotifyWaitObjectListeners(&WaitObjectListener::RWLockInitialized, lock);
}
@ -252,8 +262,8 @@ rw_lock_destroy(rw_lock* lock)
InterruptsSpinLocker locker(gThreadSpinlock);
#if KDEBUG
if (lock->waiters != NULL && thread_get_current_thread_id()
!= lock->holder) {
if (lock->waiters != NULL
&& thread_get_current_thread_id() != lock->holder) {
panic("rw_lock_destroy(): there are blocking threads, but the caller "
"doesn't hold the write lock (%p)", lock);
@ -275,6 +285,7 @@ rw_lock_destroy(rw_lock* lock)
lock->name = NULL;
locker.Unlock();
mutex_destroy(&lock->lock);
free(name);
}
@ -286,7 +297,7 @@ rw_lock_read_lock(rw_lock* lock)
#if KDEBUG_RW_LOCK_DEBUG
return rw_lock_write_lock(lock);
#else
InterruptsSpinLocker locker(gThreadSpinlock);
MutexLocker locker(lock->lock);
if (lock->writer_count == 0) {
lock->reader_count++;
@ -297,6 +308,8 @@ rw_lock_read_lock(rw_lock* lock)
return B_OK;
}
locker.Detach();
return rw_lock_wait(lock, false);
#endif
}
@ -308,7 +321,7 @@ rw_lock_read_unlock(rw_lock* lock)
#if KDEBUG_RW_LOCK_DEBUG
return rw_lock_write_unlock(lock);
#else
InterruptsSpinLocker locker(gThreadSpinlock);
MutexLocker locker(lock->lock);
if (lock->holder == thread_get_current_thread_id()) {
if (--lock->owner_count > 0)
@ -338,7 +351,7 @@ rw_lock_read_unlock(rw_lock* lock)
status_t
rw_lock_write_lock(rw_lock* lock)
{
InterruptsSpinLocker locker(gThreadSpinlock);
MutexLocker locker(lock->lock);
if (lock->reader_count == 0 && lock->writer_count == 0) {
lock->writer_count++;
@ -352,6 +365,7 @@ rw_lock_write_lock(rw_lock* lock)
}
lock->writer_count++;
locker.Detach();
status_t status = rw_lock_wait(lock, true);
if (status == B_OK) {
@ -365,7 +379,7 @@ rw_lock_write_lock(rw_lock* lock)
status_t
rw_lock_write_unlock(rw_lock* lock)
{
InterruptsSpinLocker locker(gThreadSpinlock);
MutexLocker locker(lock->lock);
if (thread_get_current_thread_id() != lock->holder) {
panic("rw_lock_write_unlock(): lock %p not write-locked by this thread",