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Comment:Avoid a mutex in-and-out in unixShmBarrier() on this branch. Use __sync_synchronize() instead.
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SHA3-256: 280d1a72dc269b4402853159949d7a905d414786074f5d80e951c9341ebbd1b5
User & Date: dan 2018-12-10 09:36:34
Context
2018-12-10
15:58
Merge the latest version of mutexfree-shmlock with this branch. check-in: 6007abfe user: dan tags: begin-concurrent-pnu-mutexfree-shmlock
09:45
Avoid a mutex in-and-out in unixShmBarrier() on this branch. Use __sync_synchronize() instead. check-in: a8c5fd86 user: dan tags: mutexfree-shmlock
09:36
Avoid a mutex in-and-out in unixShmBarrier() on this branch. Use __sync_synchronize() instead. check-in: 280d1a72 user: dan tags: begin-concurrent-pnu-mutexfree-shmlock
2018-12-06
20:26
Add the mutexfree-shmlock experiment to the begin-concurrent-pnu branch. check-in: 3aead209 user: dan tags: begin-concurrent-pnu-mutexfree-shmlock
Changes
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Changes to src/os_unix.c.

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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);



  sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
  assert( fd->pMethods->xLock==nolockLock 
       || unixFileMutexNotheld((unixFile*)fd) 
  );
  unixEnterMutex();               /* Also mutex, for redundancy */
  unixLeaveMutex();

}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**
** If there is no shared memory associated with the connection then this







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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);
#ifdef SQLITE_MUTEXFREE_SHMLOCK
  __sync_synchronize();
#else
  sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
  assert( fd->pMethods->xLock==nolockLock 
       || unixFileMutexNotheld((unixFile*)fd) 
  );
  unixEnterMutex();               /* Also mutex, for redundancy */
  unixLeaveMutex();
#endif
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**
** If there is no shared memory associated with the connection then this