/*

 * Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "runtime/threadLocalStorage.hpp"

#ifdef AMD64

extern "C" Thread*  fs_load(ptrdiff_t tlsOffset);

extern "C" intptr_t fs_thread();

#else

// From solaris_i486.s

extern "C" Thread*  gs_load(ptrdiff_t tlsOffset);

extern "C" intptr_t gs_thread();

#endif // AMD64

// tlsMode encoding:

//

// pd_tlsAccessUndefined : uninitialized

// pd_tlsAccessSlow      : not available

// pd_tlsAccessIndirect  :

//   old-style indirect access - present in "T1" libthread.

//   use thr_slot_sync_allocate() to attempt to allocate a slot.

// pd_tlsAccessDirect    :

//   new-style direct access - present in late-model "T2" libthread.

//   Allocate the offset (slot) via _thr_slot_offset() or by

//   defining an IE- or LE-mode TLS/TSD slot in the launcher and then passing

//   that offset into libjvm.so.

//   See http://sac.eng/Archives/CaseLog/arc/PSARC/2003/159/.

//

// Note that we have a capability gap - some early model T2 forms

// (e.g., unpatched S9) have neither _thr_slot_sync_allocate() nor

// _thr_slot_offset().  In that case we revert to the usual

// thr_getspecific accessor.

//

static ThreadLocalStorage::pd_tlsAccessMode tlsMode = ThreadLocalStorage::pd_tlsAccessUndefined ;

static ptrdiff_t tlsOffset = 0 ;

static thread_key_t tlsKey ;

typedef int (*TSSA_Entry) (ptrdiff_t *, int, int) ;

typedef ptrdiff_t (*TSO_Entry) (int) ;

ThreadLocalStorage::pd_tlsAccessMode ThreadLocalStorage::pd_getTlsAccessMode ()

{

   guarantee (tlsMode != pd_tlsAccessUndefined, "tlsMode not set") ;

   return tlsMode ;

}

ptrdiff_t ThreadLocalStorage::pd_getTlsOffset () {

   guarantee (tlsMode != pd_tlsAccessUndefined, "tlsMode not set") ;

   return tlsOffset ;

}

// TODO: Consider the following improvements:

//

// 1.   Convert from thr_*specific* to pthread_*specific*.

//      The pthread_ forms are slightly faster.  Also, the

//      pthread_ forms have a pthread_key_delete() API which

//      would aid in clean JVM shutdown and the eventual goal

//      of permitting a JVM to reinstantiate itself withing a process.

//

// 2.   See ThreadLocalStorage::init().  We end up allocating

//      two TLS keys during VM startup.  That's benign, but we could collapse

//      down to one key without too much trouble.

//

// 3.   MacroAssembler::get_thread() currently emits calls to thr_getspecific().

//      Modify get_thread() to call Thread::current() instead.

//

// 4.   Thread::current() currently uses a cache keyed by %gs:[0].

//      (The JVM has PSARC permission to use %g7/%gs:[0]

//      as an opaque temporally unique thread identifier).

//      For C++ access to a thread's reflexive "self" pointer we

//      should consider using one of the following:

//      a. a radix tree keyed by %esp - as in EVM.

//         This requires two loads (the 2nd dependent on the 1st), but

//         is easily inlined and doesn't require a "miss" slow path.

//      b. a fast TLS/TSD slot allocated by _thr_slot_offset

//         or _thr_slot_sync_allocate.

//

// 5.   'generate_code_for_get_thread' is a misnomer.

//      We should change it to something more general like

//      pd_ThreadSelf_Init(), for instance.

//

static void AllocateTLSOffset ()

{

   int rslt ;

   TSSA_Entry tssa ;

   TSO_Entry  tso ;

   ptrdiff_t off ;

   guarantee (tlsMode == ThreadLocalStorage::pd_tlsAccessUndefined, "tlsMode not set") ;

   tlsMode = ThreadLocalStorage::pd_tlsAccessSlow ;

   tlsOffset = 0 ;

#ifndef AMD64

   tssa = (TSSA_Entry) dlsym (RTLD_DEFAULT, "thr_slot_sync_allocate") ;

   if (tssa != NULL) {

        off = -1 ;

        rslt = (*tssa)(&off, NULL, NULL) ;                // (off,dtor,darg)

        if (off != -1) {

           tlsOffset = off ;

           tlsMode = ThreadLocalStorage::pd_tlsAccessIndirect ;

           return ;

        }

    }

    rslt = thr_keycreate (&tlsKey, NULL) ;

    if (rslt != 0) {

        tlsMode = ThreadLocalStorage::pd_tlsAccessSlow ;   // revert to slow mode

        return ;

    }

    tso = (TSO_Entry) dlsym (RTLD_DEFAULT, "_thr_slot_offset") ;

    if (tso != NULL) {

        off = (*tso)(tlsKey) ;

        if (off >= 0) {

           tlsOffset = off ;

           tlsMode = ThreadLocalStorage::pd_tlsAccessDirect ;

           return ;

        }

    }

    // Failure: Too bad ... we've allocated a TLS slot we don't need and there's

    // no provision in the ABI for returning the slot.

    //

    // If we didn't find a slot then then:

    // 1. We might be on liblwp.

    // 2. We might be on T2 libthread, but all "fast" slots are already

    //    consumed

    // 3. We might be on T1, and all TSD (thr_slot_sync_allocate) slots are

    //    consumed.

    // 4. We might be on T2 libthread, but it's be re-architected

    //    so that fast slots are no longer g7-relative.

    //

    tlsMode = ThreadLocalStorage::pd_tlsAccessSlow ;

    return ;

#endif // AMD64

}

void ThreadLocalStorage::generate_code_for_get_thread() {

    AllocateTLSOffset() ;

}

void ThreadLocalStorage::set_thread_in_slot(Thread *thread) {

  guarantee (tlsMode != pd_tlsAccessUndefined, "tlsMode not set") ;

  if (tlsMode == pd_tlsAccessIndirect) {

#ifdef AMD64

        intptr_t tbase = fs_thread();

#else

        intptr_t tbase = gs_thread();

#endif // AMD64

        *((Thread**) (tbase + tlsOffset)) = thread ;

  } else

  if (tlsMode == pd_tlsAccessDirect) {

        thr_setspecific (tlsKey, (void *) thread) ;

        // set with thr_setspecific and then readback with gs_load to validate.

#ifdef AMD64

        guarantee (thread == fs_load(tlsOffset), "tls readback failure") ;

#else

        guarantee (thread == gs_load(tlsOffset), "tls readback failure") ;

#endif // AMD64

  }

}

extern "C" Thread* get_thread() {

  return ThreadLocalStorage::thread();

}