170 lines
3.9 KiB
C++
170 lines
3.9 KiB
C++
// natThreadLocal.cc - Native part of ThreadLocal class.
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// Fast thread local storage for systems that support the __thread
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// variable attribute.
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/* Copyright (C) 2006 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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#include <config.h>
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#include <stdlib.h>
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#include <gcj/cni.h>
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#include <jvm.h>
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#include <java-threads.h>
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#include <gnu/gcj/RawDataManaged.h>
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#include <java/lang/ThreadLocal.h>
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#include <java/lang/IllegalArgumentException.h>
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#include <java/lang/IllegalThreadStateException.h>
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#include <java/lang/InterruptedException.h>
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#include <java/util/Map.h>
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#include <jni.h>
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/* We would like to have fast thread local variables that behave in
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the same way as C and C++ thread local variables. This would mean
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having an field attribute "thread" (like static, final, etc.).
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However, this is not compatible with java semantics, which we wish
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to support transparently. The problems we must overcome are:
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* In Java, ThreadLocal variables are not statically allocated: they
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are objects, created at runtime.
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* Class ThreadLocal is not final and neither are its methods, so it
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is possible to create a subclass of ThreadLocal that overrides
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any method.
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* __thread variables in DSOs are not visible to the garbage
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collector, so we must ensure that we keep a copy of every thread
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local variable somewhere on the heap.
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* Once a ThreadLocal instance has been created and assigned to a
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static field, that field may be reassigned to a different
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ThreadLocal instance or null.
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So, we can't simply replace get() and set() with accesses of a
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__thread variable.
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So, we create a pthread_key in each ThreadLocal object and use that
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as a kind of "look-aside cache". When a ThreadLocal is set, we
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also set the corresponding thread-specific value. When the
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ThreadLocal is collected, we delete the key.
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This scheme is biased towards efficiency when get() is called much
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more frequently than set(). It is slightly internaler than the
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all-Java solution using the underlying map in the set() case.
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However, get() is very much more frequently invoked than set().
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*/
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#ifdef _POSIX_PTHREAD_SEMANTICS
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class tls_t
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{
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public:
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pthread_key_t key;
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};
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void
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java::lang::ThreadLocal::constructNative (void)
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{
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tls_t *tls = (tls_t *)_Jv_Malloc (sizeof (tls_t));
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if (pthread_key_create (&tls->key, NULL) == 0)
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TLSPointer = (::gnu::gcj::RawData *)tls;
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else
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_Jv_Free (tls);
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}
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void
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java::lang::ThreadLocal::set (::java::lang::Object *value)
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{
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if (TLSPointer != NULL)
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{
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tls_t* tls = (tls_t*)TLSPointer;
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pthread_setspecific (tls->key, value);
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}
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internalSet (value);
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}
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::java::lang::Object *
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java::lang::ThreadLocal::get (void)
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{
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if (TLSPointer == NULL)
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return internalGet ();
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tls_t* tls = (tls_t*)TLSPointer;
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void *obj = pthread_getspecific(tls->key);
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if (obj)
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return (::java::lang::Object *)obj;
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::java::lang::Object *value = internalGet ();
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pthread_setspecific (tls->key, value);
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return value;
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}
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void
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java::lang::ThreadLocal::remove (void)
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{
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if (TLSPointer != NULL)
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{
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tls_t* tls = (tls_t*)TLSPointer;
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pthread_setspecific (tls->key, NULL);
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}
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internalRemove ();
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}
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void
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java::lang::ThreadLocal::finalize (void)
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{
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if (TLSPointer != NULL)
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{
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tls_t* tls = (tls_t*)TLSPointer;
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pthread_key_delete (tls->key);
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_Jv_Free (tls);
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}
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}
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#else
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void
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java::lang::ThreadLocal::constructNative (void)
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{
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}
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void
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java::lang::ThreadLocal::set (::java::lang::Object *value)
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{
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internalSet (value);
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}
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::java::lang::Object *
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java::lang::ThreadLocal::get (void)
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{
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return internalGet ();
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}
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void
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java::lang::ThreadLocal::remove (void)
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{
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internalRemove ();
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}
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void
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java::lang::ThreadLocal::finalize (void)
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{
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}
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#endif
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