Re: SR standby hangs

On 04/26/2011 04:28 PM, Tom Lane wrote:
> Andrew Dunstan<andrew(at)dunslane(dot)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