From b66950bc26cfb3210e786c966141b20a5cc13a84 Mon Sep 17 00:00:00 2001
From: Aleric Inglewood
Date: Wed, 10 Nov 2010 15:19:13 +0100
Subject: IMP-590: Added a thread-safe and robust wrapper for APR pools.
See http://redmine.imprudenceviewer.org/issues/590
---
linden/indra/llcommon/aiaprpool.cpp | 198 ++++++++++++++++++++++++++++++++++++
1 file changed, 198 insertions(+)
create mode 100644 linden/indra/llcommon/aiaprpool.cpp
(limited to 'linden/indra/llcommon/aiaprpool.cpp')
diff --git a/linden/indra/llcommon/aiaprpool.cpp b/linden/indra/llcommon/aiaprpool.cpp
new file mode 100644
index 0000000..d3748e9
--- /dev/null
+++ b/linden/indra/llcommon/aiaprpool.cpp
@@ -0,0 +1,198 @@
+/**
+ * @file aiaprpool.cpp
+ *
+ * Copyright (c) 2010, Aleric Inglewood.
+ *
+ * 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.
+ *
+ * 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, see .
+ *
+ * There are special exceptions to the terms and conditions of the GPL as
+ * it is applied to this Source Code. View the full text of the exception
+ * in the file doc/FLOSS-exception.txt in this software distribution.
+ *
+ * CHANGELOG
+ * and additional copyright holders.
+ *
+ * 04/04/2010
+ * - Initial version, written by Aleric Inglewood @ SL
+ *
+ * 10/11/2010
+ * - Changed filename, class names and license to a more
+ * company-neutral format.
+ * - Added APR_HAS_THREADS #if's to allow creation and destruction
+ * of subpools by threads other than the parent pool owner.
+ */
+
+#include "linden_common.h"
+
+#include "llerror.h"
+#include "aiaprpool.h"
+#include "llthread.h"
+
+// Create a subpool from parent.
+void AIAPRPool::create(AIAPRPool& parent)
+{
+ llassert(!mPool); // Must be non-initialized.
+ mParent = &parent;
+ if (!mParent) // Using the default parameter?
+ {
+ // By default use the root pool of the current thread.
+ mParent = &AIThreadLocalData::tldata().mRootPool;
+ }
+ llassert(mParent->mPool); // Parent must be initialized.
+#if APR_HAS_THREADS
+ // As per the documentation of APR (ie http://apr.apache.org/docs/apr/1.4/apr__pools_8h.html):
+ //
+ // Note that most operations on pools are not thread-safe: a single pool should only be
+ // accessed by a single thread at any given time. The one exception to this rule is creating
+ // a subpool of a given pool: one or more threads can safely create subpools at the same
+ // time that another thread accesses the parent pool.
+ //
+ // In other words, it's safe for any thread to create a (sub)pool, independent of who
+ // owns the parent pool.
+ mOwner = apr_os_thread_current();
+#else
+ mOwner = mParent->mOwner;
+ llassert(apr_os_thread_equal(mOwner, apr_os_thread_current()));
+#endif
+ apr_status_t const apr_pool_create_status = apr_pool_create(&mPool, mParent->mPool);
+ llassert_always(apr_pool_create_status == APR_SUCCESS);
+ llassert(mPool); // Initialized.
+ apr_pool_cleanup_register(mPool, this, &s_plain_cleanup, &apr_pool_cleanup_null);
+}
+
+// Destroy the (sub)pool, if any.
+void AIAPRPool::destroy(void)
+{
+ // Only do anything if we are not already (being) destroyed.
+ if (mPool)
+ {
+#if !APR_HAS_THREADS
+ // If we are a root pool, then every thread may destruct us: in that case
+ // we have to assume that no other thread will use this pool concurrently,
+ // of course. Otherwise, if we are a subpool, only the thread that owns
+ // the parent may destruct us, since that is the pool that is still alive,
+ // possibly being used by others and being altered here.
+ llassert(!mParent || apr_os_thread_equal(mParent->mOwner, apr_os_thread_current()));
+#endif
+ apr_pool_t* pool = mPool;
+ mPool = NULL; // Mark that we are BEING destructed.
+ apr_pool_cleanup_kill(pool, this, &s_plain_cleanup);
+ apr_pool_destroy(pool);
+ }
+}
+
+bool AIAPRPool::parent_is_being_destructed(void)
+{
+ return mParent && (!mParent->mPool || mParent->parent_is_being_destructed());
+}
+
+AIAPRInitialization::AIAPRInitialization(void)
+{
+ static bool apr_initialized = false;
+
+ if (!apr_initialized)
+ {
+ apr_initialize();
+ }
+
+ apr_initialized = true;
+}
+
+bool AIAPRRootPool::sCountInitialized = false;
+apr_uint32_t volatile AIAPRRootPool::sCount;
+
+extern apr_thread_mutex_t* gLogMutexp;
+extern apr_thread_mutex_t* gCallStacksLogMutexp;
+
+AIAPRRootPool::AIAPRRootPool(void) : AIAPRInitialization(), AIAPRPool(0)
+{
+ // sCountInitialized don't need locking because when we get here there is still only a single thread.
+ if (!sCountInitialized)
+ {
+ // Initialize the logging mutex
+ apr_thread_mutex_create(&gLogMutexp, APR_THREAD_MUTEX_UNNESTED, mPool);
+ apr_thread_mutex_create(&gCallStacksLogMutexp, APR_THREAD_MUTEX_UNNESTED, mPool);
+
+ apr_status_t status = apr_atomic_init(mPool);
+ llassert_always(status == APR_SUCCESS);
+ apr_atomic_set32(&sCount, 1); // Set to 1 to account for the global root pool.
+ sCountInitialized = true;
+
+ // Initialize thread-local APR pool support.
+ // Because this recursively calls AIAPRRootPool::AIAPRRootPool(void)
+ // it must be done last, so that sCount is already initialized.
+ AIThreadLocalData::init();
+ }
+ apr_atomic_inc32(&sCount);
+}
+
+AIAPRRootPool::~AIAPRRootPool()
+{
+ if (!apr_atomic_dec32(&sCount))
+ {
+ // The last pool was destructed. Cleanup remainder of APR.
+ LL_INFOS("APR") << "Cleaning up APR" << LL_ENDL;
+
+ if (gLogMutexp)
+ {
+ // Clean up the logging mutex
+
+ // All other threads NEED to be done before we clean up APR, so this is okay.
+ apr_thread_mutex_destroy(gLogMutexp);
+ gLogMutexp = NULL;
+ }
+ if (gCallStacksLogMutexp)
+ {
+ // Clean up the logging mutex
+
+ // All other threads NEED to be done before we clean up APR, so this is okay.
+ apr_thread_mutex_destroy(gCallStacksLogMutexp);
+ gCallStacksLogMutexp = NULL;
+ }
+
+ // Must destroy ALL, and therefore this last AIAPRRootPool, before terminating APR.
+ static_cast(this)->destroy();
+
+ apr_terminate();
+ }
+}
+
+//static
+AIAPRRootPool& AIAPRRootPool::get(void)
+{
+ static AIAPRRootPool global_APRpool(0); // This is what used to be gAPRPoolp.
+ return global_APRpool;
+}
+
+void AIVolatileAPRPool::clearVolatileAPRPool()
+{
+ llassert_always(mNumActiveRef > 0);
+ if (--mNumActiveRef == 0)
+ {
+ if (isOld())
+ {
+ destroy();
+ mNumTotalRef = 0 ;
+ }
+ else
+ {
+ // This does not actually free the memory,
+ // it just allows the pool to re-use this memory for the next allocation.
+ clear();
+ }
+ }
+
+ // Paranoia check if the pool is jammed.
+ llassert(mNumTotalRef < (FULL_VOLATILE_APR_POOL << 2)) ;
+}
--
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