sosend returning ERESTART

[Colin Percival]

On 01/17/17 02:06, Konstantin Belousov wrote:
> On Tue, Jan 17, 2017 at 04:57:23AM +0000, Colin Percival wrote:
>> I think I've tracked an NFS problem down to sosend returning ERESTART; it
>> looks like it's easy to work around this, but I'm not sure *why* sosend is
>> returning ERESTART... or for that matter *how* since I can't find anywhere
>> in relevant code where that gets returned.
> ERESTART is most likely returned by msleep(9) or similar call down the
> path when unblocked signal is pending with the restart disposition.

Thanks, looks like that was exactly it -- if the TCP send buffer was full
we would call sbwait, and if a signal arrived it would return ERESTART.
It looks like setting the SB_NOINTR flag will prevent this; I'm testing a
patch right now.

(Google bait in case anyone else trips over this: FreeBSD 11.0 NFS client
dropping TCP connections under concurrent I/O load.)

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid