The Tor Browser: build/stlport/src/lock_free_slist.h@141e0f1194b1 (annotated)

build/stlport/src/lock_free_slist.h@141e0f1194b1 (annotated)

build/stlport/src/lock_free_slist.h

Wed, 31 Dec 2014 07:16:47 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 07:16:47 +0100
branch: TOR_BUG_9701
changeset 3: 141e0f1194b1
permissions: -rw-r--r--

Revert simplistic fix pending revisit of Mozilla integration attempt.

 /*
  * Copyright (c) 1997-1999
  * Silicon Graphics Computer Systems, Inc.
  *
  * Copyright (c) 1999
  * Boris Fomitchev
  *
  * This material is provided "as is", with absolutely no warranty expressed
  * or implied. Any use is at your own risk.
  *
  * Permission to use or copy this software for any purpose is hereby granted
  * without fee, provided the above notices are retained on all copies.
  * Permission to modify the code and to distribute modified code is granted,
  * provided the above notices are retained, and a notice that the code was
  * modified is included with the above copyright notice.
  *
  */
 #ifndef _STLP_LOCK_FREE_SLIST_H
 #define _STLP_LOCK_FREE_SLIST_H
 #if defined(_STLP_PTHREADS)
 #  include <pthread.h>
 #  if defined (__GNUC__) && defined (__i386__)
 #    define _STLP_HAS_ATOMIC_FREELIST
 /**
  * Class that implements a non-blocking and thread-safe freelist.
  * It is used for the lock-free node allocation engine.
  *
  * @author felixw@inin.com
  */
 class _STLP_atomic_freelist {
 public:
   /**
    * Type representing items of the freelist
    */
   struct item {
     item* _M_next;
   };
   _STLP_atomic_freelist() {
     // Statically assert layout of member is as expected by assembly code
     _STLP_STATIC_ASSERT(sizeof(_M) == 8)
     _M._M_data._M_top       = 0;
     _M._M_data._M_sequence  = 0;
   }
   /**
    * Atomically pushes the specified item onto the freelist.
    *
    * @param __item [in] Item to add to the front of the list
    */
   void push(item* __item) {
     // NOTE: GCC uses ebx as the PIC register for globals in shared libraries.
     //       The GCC version I'm using (3.4.1) won't temporarily spill it if it's
     //       used as input, output, or clobber.  Instead, it complains with a
     //       "can't find a register in class `BREG' while reloading `asm'" error.
     //       This is probably a compiler bug, but as the cmpxchg8b instruction
     //       requires ebx, I work around this here by using ecx for the '__item'
     //       input and spilling ebx into edi.  This also precludes us from using
     //       a "m" operand for the cmpxchg8b argument (GCC might think it can make
     //       it relative to ebx).  Instead, we're using esi for the address of _M_data.
     //
     int __tmp1;     // These dummy variables are used to tell GCC that the eax, ecx,
     int __tmp2;     // and edx registers will not have the same value as their input.
     int __tmp3;     // The optimizer will remove them as their values are not used.
     __asm__ __volatile__
       ("       movl       %%ebx, %%edi\n\t"
        "       movl       %%ecx, %%ebx\n\t"
        "L1_%=: movl       %%eax, (%%ebx)\n\t"     // __item._M_next = _M._M_data._M_top
        "       leal       1(%%edx),%%ecx\n\t"     // new sequence = _M._M_data._M_sequence + 1
        "lock;  cmpxchg8b  (%%esi)\n\t"
        "       jne        L1_%=\n\t"              // Failed, retry! (edx:eax now contain most recent _M_sequence:_M_top)
        "       movl       %%edi, %%ebx"
       :"=a" (__tmp1), "=d" (__tmp2), "=c" (__tmp3)
       :"a" (_M._M_data._M_top), "d" (_M._M_data._M_sequence), "c" (__item), "S" (&_M._M_data)
       :"edi", "memory", "cc");
   }
   /**
    * Atomically removes the topmost item from the freelist and returns a
    * pointer to it.  Returns NULL if the list is empty.
    *
    * @return Item that was removed from front of list; NULL if list empty
    */
   item* pop() {
     item*   __result;
     int     __tmp;
     __asm__ __volatile__
       ("       movl       %%ebx, %%edi\n\t"
        "L1_%=: testl      %%eax, %%eax\n\t"       // _M_top == NULL?
        "       je         L2_%=\n\t"              // If yes, we're done
        "       movl       (%%eax), %%ebx\n\t"     // new top = _M._M_data._M_top->_M_next
        "       leal       1(%%edx),%%ecx\n\t"     // new sequence = _M._M_data._M_sequence + 1
        "lock;  cmpxchg8b  (%%esi)\n\t"
        "       jne        L1_%=\n\t"              // We failed, retry! (edx:eax now contain most recent _M_sequence:_M_top)
        "L2_%=: movl       %%edi, %%ebx"
       :"=a" (__result), "=d" (__tmp)
       :"a" (_M._M_data._M_top), "d" (_M._M_data._M_sequence), "S" (&_M._M_data)
       :"edi", "ecx", "memory", "cc");
     return __result;
   }
   /**
    * Atomically detaches all items from the list and returns a pointer to the
    * topmost item.  The items are still chained and may be traversed safely as
    * they're now "owned" by the calling thread.
    *
    * @return Pointer to topmost item in the list; NULL if list empty
    */
   item* clear() {
     item*   __result;
     int     __tmp;
     __asm__ __volatile__
       ("       movl       %%ebx, %%edi\n\t"
        "L1_%=: testl      %%eax, %%eax\n\t"       // _M_top == NULL?
        "       je         L2_%=\n\t"              // If yes, we're done
        "       xorl       %%ebx, %%ebx\n\t"       // We're attempting to set _M_top to NULL
        "       leal       1(%%edx),%%ecx\n\t"     // new sequence = _M._M_data._M_sequence + 1
        "lock;  cmpxchg8b  (%%esi)\n\t"
        "       jne        L1_%=\n\t"              // Failed, retry! (edx:eax now contain most recent _M_sequence:_M_top)
        "L2_%=: movl       %%edi, %%ebx"
       :"=a" (__result), "=d" (__tmp)
       :"a" (_M._M_data._M_top), "d" (_M._M_data._M_sequence), "S" (&_M._M_data)
       :"edi", "ecx", "memory", "cc");
     return __result;
   }
 private:
     union {
       long long   _M_align;
       struct {
         item*           _M_top;         // Topmost element in the freelist
         unsigned int    _M_sequence;    // Sequence counter to prevent "ABA problem"
       } _M_data;
     } _M;
   _STLP_atomic_freelist(const _STLP_atomic_freelist&);
   _STLP_atomic_freelist& operator=(const _STLP_atomic_freelist&);
 };
 #  endif /* if defined(__GNUC__) && defined(__i386__) */
 #elif defined (_STLP_WIN32THREADS)
 #  if !defined (_WIN64)
 #    define _STLP_USE_ASM_IMPLEMENTATION
 #  endif
 // Here are the compiler/platform requirements for the thread safe and
 // lock free singly linked list implementation:
 #  if defined (_STLP_USE_ASM_IMPLEMENTATION)
 // For the asm version:
 #    if defined (_STLP_MSVC) && defined (_M_IX86) && (_M_IX86 >= 500)
 #      define _STLP_HAS_ATOMIC_FREELIST
 #    endif
 #  else
 // For the API based version:
 #    if defined (_STLP_NEW_PLATFORM_SDK) && (!defined (WINVER) || (WINVER >= 0x0501)) && \
                                             (!defined (_WIN32_WINNT) || (_WIN32_WINNT >= 0x0501))
 #      define _STLP_HAS_ATOMIC_FREELIST
 #    endif
 #  endif
 #  if defined (_STLP_HAS_ATOMIC_FREELIST)
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
 #      if defined (_STLP_MSVC) && (_STLP_MSVC < 1300) || defined (__ICL)
 #        pragma warning (push)
 #        pragma warning (disable : 4035) //function has no return value
 #      endif
 #    endif
 /**
  * Class that implements a non-blocking and thread-safe freelist.
  * It is used for the lock-free node allocation engine.
  *
  * @author felixw@inin.com
  */
 class _STLP_atomic_freelist {
 public:
   /**
    * Type representing items of the freelist
    */
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
   struct item {
       item*   _M_next;
   };
 #    else
   typedef SLIST_ENTRY item;
 #    endif
   _STLP_atomic_freelist() {
     // Statically assert layout of member is as expected by assembly code
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
     _STLP_STATIC_ASSERT((sizeof(item) == sizeof(item*)) && (sizeof(_M) == 8))
     _M._M_data._M_top       = 0;
     _M._M_data._M_sequence  = 0;
 #    else
     InitializeSListHead(&_M_head);
 #    endif
   }
   /**
    * Atomically pushes the specified item onto the freelist.
    *
    * @param __item [in] Item to add to the front of the list
    */
   void push(item* __item) {
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
     __asm
     {
         mov             esi, this
         mov             ebx, __item
         mov             eax, [esi]              // _M._M_data._M_top
         mov             edx, [esi+4]            // _M._M_data._M_sequence
     L1: mov             [ebx], eax              // __item._M_next = _M._M_data._M_top
         lea             ecx, [edx+1]            // new sequence = _M._M_data._M_sequence + 1
         lock cmpxchg8b  qword ptr [esi]
         jne             L1                      // Failed, retry! (edx:eax now contain most recent _M_sequence:_M_top)
     }
 #    else
     InterlockedPushEntrySList(&_M_head, __item);
 #    endif
   }
   /**
    * Atomically removes the topmost item from the freelist and returns a
    * pointer to it.  Returns NULL if the list is empty.
    *
    * @return Item that was removed from front of list; NULL if list empty
    */
   item* pop() {
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
     __asm
     {
         mov             esi, this
         mov             eax, [esi]              // _M._M_data._M_top
         mov             edx, [esi+4]            // _M._M_data._M_sequence
     L1: test            eax, eax                // _M_top == NULL?
         je              L2                      // Yes, we're done
         mov             ebx, [eax]              // new top = _M._M_data._M_top->_M_next
         lea             ecx, [edx+1]            // new sequence = _M._M_data._M_sequence + 1
         lock cmpxchg8b  qword ptr [esi]
         jne             L1                      // Failed, retry! (edx:eax now contain most recent _M_sequence:_M_top)
     L2:
     }
 #    else
     return InterlockedPopEntrySList(&_M_head);
 #    endif
   }
   /**
    * Atomically detaches all items from the list and returns pointer to the
    * topmost.  The items are still chained and may be traversed safely as
    * they're now "owned" by the calling thread.
    *
    * @return Pointer to topmost item in the list; NULL if list empty
    */
   item* clear() {
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
     __asm
     {
         mov             esi, this
         mov             eax, [esi]              // _M._M_data._M_top
         mov             edx, [esi+4]            // _M._M_data._M_sequence
     L1: test            eax, eax                // _M_top == NULL?
         je              L2                      // Yes, we're done
         xor             ebx,ebx                 // We're attempting to set _M._M_data._M_top to NULL
         lea             ecx, [edx+1]            // new sequence = _M._M_data._M_sequence + 1
         lock cmpxchg8b  qword ptr [esi]
         jne             L1                      // Failed, retry! (edx:eax now contain most recent _M_sequence:_M_top)
     L2:
     }
 #    else
     return InterlockedFlushSList(&_M_head);
 #    endif
   }
 private:
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
   union {
     __int64     _M_align;
     struct {
       item*           _M_top;         // Topmost element in the freelist
       unsigned int    _M_sequence;    // Sequence counter to prevent "ABA problem"
     } _M_data;
   } _M;
 #    else
   SLIST_HEADER _M_head;
 #    endif
   _STLP_atomic_freelist(const _STLP_atomic_freelist&);
   _STLP_atomic_freelist& operator = (const _STLP_atomic_freelist&);
 };
 #    if defined (_STLP_USE_ASM_IMPLEMENTATION)
 #      if defined (_STLP_MSVC) && (_STLP_MSVC < 1300) || defined (__ICL)
 #        pragma warning (pop)
 #      endif
 #    endif
 #  endif /* _STLP_HAS_ATOMIC_FREELIST */
 #endif
 #endif /* _STLP_LOCK_FREE_SLIST_H */

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build/stlport/src/lock_free_slist.h@141e0f1194b1 (annotated)

build/stlport/src/lock_free_slist.h