Thread: ? potential bug in LockBuffer ?

Folks: As I study the source of LockBuffer in bufmgr.c I came across
the following code snippet for the case of releasing a
shared (read) lock:

       if (mode == BUFFER_LOCK_UNLOCK)       {               if (*buflock & BL_R_LOCK)               {
    Assert(buf->r_locks > 0);                       Assert(!(buf->w_lock));                       Assert(!(*buflock &
(BL_W_LOCK| BL_RI_LOCK)));                       (buf->r_locks)--;                        *buflock &= ~BL_R_LOCK;
 

This code resets BL_R_LOCK on the first release of a shared lock.
I think it should check that the count of readers be zero:
( something like
       if (mode == BUFFER_LOCK_UNLOCK)       {               if (*buflock & BL_R_LOCK)               {
    Assert(buf->r_locks > 0);                       Assert(!(buf->w_lock));                       Assert(!(*buflock &
(BL_W_LOCK| BL_RI_LOCK)));                       (buf->r_locks)--;                       if (!buf->r_locks)
                 *buflock &= ~BL_R_LOCK;
 


Or I am missing something...
      thanks           regards                  Mauricio
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>                         (buf->r_locks)--;
>                         if (!buf->r_locks)
>                                 *buflock &= ~BL_R_LOCK;
> 
> 
> Or I am missing something...

buflock is per-backend flag, it's not in shmem. Backend is
allowed only single lock per buffer.

Vadim