Re: Anti-critical-section assertion failure in mcxt.c reached by walsender

On Sat, May 8, 2021 at 2:30 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> May 07 03:31:39 gcc202 kernel: sunvdc: vdc_tx_trigger() failure, err=-11

That's -EAGAIN (assuming errnos match x86) and I guess it indicates
that VDC_MAX_RETRIES is exceeded here:

https://github.com/torvalds/linux/blob/master/drivers/block/sunvdc.c#L451
https://github.com/torvalds/linux/blob/master/drivers/block/sunvdc.c#L526

One theory is that the hypervisor/host is occasionally too swamped to
service the request queue fast enough over a ~10ms period, given that
vio_ldc_send() itself retries 1000 times with a 1us sleep, the outer
loop tries ten times, and ldc.c's write_nonraw() reports -EAGAIN when
there is no space for the message.  (Alternatively, it's trying to
send a message that's too big for the channel, the channel is
corrupted by bugs, or my fly-by of this code I'd never heard of before
now is just way off...)