linux-kernel - Re: [PATCH] tools: hv: ignore ENOBUFS in the KVP daemon

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Message-ID: <87lhn7forv.fsf@vitty.brq.redhat.com>
Date:	Wed, 19 Nov 2014 11:49:56 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	Dexuan Cui <decui@...rosoft.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	driverdev-devel@...uxdriverproject.org, olaf@...fle.de,
	apw@...onical.com, jasowang@...hat.com, haiyangz@...rosoft.com
Subject: Re: [PATCH] tools: hv: ignore ENOBUFS in the KVP daemon

Dexuan Cui <decui@...rosoft.com> writes:

> Under high memory pressure and very high KVP R/W test pressure, the netlink
> recvfrom() may transiently return ENOBUFS to the daemon -- we found this
> during a 2-week stress test.
>
> We'd better not terminate the daemon on this failure, because a typical KVP
> user can re-try the R/W and hopefully it will succeed next time.
>
> Cc: K. Y. Srinivasan <kys@...rosoft.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>  tools/hv/hv_kvp_daemon.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
> index 22b0764..9f4b303 100644
> --- a/tools/hv/hv_kvp_daemon.c
> +++ b/tools/hv/hv_kvp_daemon.c
> @@ -1559,8 +1559,15 @@ int main(int argc, char *argv[])
>  				addr_p, &addr_l);
>
>  		if (len < 0) {
> +			int saved_errno = errno;
>  			syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s",
>  					addr.nl_pid, errno, strerror(errno));
> +
> +			if (saved_errno == ENOBUFS) {

is it possible to meet EAGAIN (or EWOULDBLOCK) here as well? I'd suggest
we ignore these as well in such case. Ignoring ENOMEM here is doubtful,
I think. But possible.

> +				syslog(LOG_ERR, "error = ENOBUFS: ignored");
> +				continue;
> +			}
> +
>  			close(fd);
>  			return -1;
>  		}

-- 
  Vitaly
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