Re: SR standby hangs

On 04/26/2011 04:28 PM, Tom Lane wrote:
> Andrew Dunstan<andrew@dunslane.net>  writes:
>> This has happened again. This time we have some debug info available,
>> and can possible get more, if people tell me what will be helpful:
>>      (gdb) f 2
>>      #2  0x00000000005de735 in LockBufferForCleanup (buffer=310163) at
>>      bufmgr.c:2432
>>      2432                ProcWaitForSignal();
>>      (gdb) p *bufHdr
>>      $2 = {tag = {rnode = {spcNode = 16393, dbNode = 40475, relNode =
>>      41880}, forkNum = MAIN_FORKNUM, blockNum = 18913}, flags = 6,
>>      usage_count = 1, refcount = 1, wait_backend_pid = 9111,
>>         buf_hdr_lock = 0 '\000', buf_id = 310162, freeNext = -2,
>>      io_in_progress_lock = 620448, content_lock = 620449}
> Well, that's pretty interesting: refcount is only 1, and the
> BM_PIN_COUNT_WAITER flag is not set.

I noticed that.

> AFAICS this *must* mean that the
> buffer had been pinned and whoever had it (presumably bgwriter) did
> UnpinBuffer().  So it appears that the signal just plain got lost :-(,
> which suggests a kernel bug.  What platform is this on, again?



CentOS 5.5, x86_64, kernel 2.6.18-194.32.1.el5

cheers

andrew