[PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka@siemens.com>

This is in line with Linux behavior.

We likely still miss an equivalent to sk_err in recvmmsg, though.

Reported-by: Lange Norbert <norbert.lange@andritz.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 kernel/cobalt/rtdm/fd.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/kernel/cobalt/rtdm/fd.c b/kernel/cobalt/rtdm/fd.c
index 0a1c6e44ed..5b2c3834da 100644
--- a/kernel/cobalt/rtdm/fd.c
+++ b/kernel/cobalt/rtdm/fd.c
@@ -734,14 +734,12 @@ int __rtdm_fd_recvmmsg(int ufd, void __user *u_msgvec, unsigned int vlen,
 		xnlock_put_irqrestore(&nklock, s);
 	}
 
-	if (datagrams > 0 &&
-	    (ret == 0 || ret == -ETIMEDOUT || ret == -EWOULDBLOCK)) {
-		/* NOTE: SO_ERROR should be honored for other errors. */
-		rtdm_fd_put(fd);
-		return datagrams;
-	}
 fail:
 	rtdm_fd_put(fd);
+
+	if (datagrams > 0)
+		ret = datagrams;
+
 out:
 	trace_cobalt_fd_recvmmsg_status(current, fd, ufd, ret);
 
@@ -826,13 +824,11 @@ int __rtdm_fd_sendmmsg(int ufd, void __user *u_msgvec, unsigned int vlen,
 		datagrams++;
 	}
 
-	if (datagrams > 0 && (ret == 0 || ret == -EWOULDBLOCK)) {
-		/* NOTE: SO_ERROR should be honored for other errors. */
-		rtdm_fd_put(fd);
-		return datagrams;
-	}
-
 	rtdm_fd_put(fd);
+
+	if (datagrams > 0)
+		ret = datagrams;
+
 out:
 	trace_cobalt_fd_sendmmsg_status(current, fd, ufd, ret);
 
-- 
2.16.4


-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

Re: [PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[Philippe Gerum]

On 11/14/19 7:59 PM, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@siemens.com>
> 
> This is in line with Linux behavior.
> 
> We likely still miss an equivalent to sk_err in recvmmsg, though.

Ack. Tracing on early exit due to null vlen in sendmmsg() is still missing; having this might help in debugging issue(s) at call site.

-- 
Philippe.

Re: [PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[Philippe Gerum]

On 11/15/19 10:37 AM, Philippe Gerum via Xenomai wrote:
> On 11/14/19 7:59 PM, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> This is in line with Linux behavior.
>>
>> We likely still miss an equivalent to sk_err in recvmmsg, though.
> 
> Ack. Tracing on early exit due to null vlen in sendmmsg() is still missing; having this might help in debugging issue(s) at call site.
> 

Likewise in recvmmsg().

-- 
Philippe.

Re: [PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[Jan Kiszka]

On 15.11.19 10:39, Philippe Gerum wrote:
> On 11/15/19 10:37 AM, Philippe Gerum via Xenomai wrote:
>> On 11/14/19 7:59 PM, Jan Kiszka wrote:
>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>
>>> This is in line with Linux behavior.
>>>
>>> We likely still miss an equivalent to sk_err in recvmmsg, though.
>>
>> Ack. Tracing on early exit due to null vlen in sendmmsg() is still missing; having this might help in debugging issue(s) at call site.
>>
> 
> Likewise in recvmmsg().
> 

Yes, I'll simply remove the "vlan == 0" optimization.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

RE: [PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[Lange Norbert]

Hello,

Just for consideration, If you can pass both error value and # of successfully sent packets out of the kernel function,
perhaps you could return the # (if > 0) and still set errno in case of an (real) error?

It would be somewhat different to Linux, but that would not be the only difference (like theres no way to block until all msgs are sent/received).

Norbert

> -----Original Message-----
> From: Xenomai <xenomai-bounces@xenomai.org> On Behalf Of Jan Kiszka
> via Xenomai
> Sent: Freitag, 15. November 2019 10:43
> To: Philippe Gerum <rpm@xenomai.org>; Xenomai
> <xenomai@xenomai.org>
> Subject: Re: [PATCH] rtdm: Do not return an error from send/recvmmsg if
> there are packets
>
> NON-ANDRITZ SOURCE: BE CAUTIOUS WITH CONTENT, LINKS OR
> ATTACHMENTS.
>
>
> On 15.11.19 10:39, Philippe Gerum wrote:
> > On 11/15/19 10:37 AM, Philippe Gerum via Xenomai wrote:
> >> On 11/14/19 7:59 PM, Jan Kiszka wrote:
> >>> From: Jan Kiszka <jan.kiszka@siemens.com>
> >>>
> >>> This is in line with Linux behavior.
> >>>
> >>> We likely still miss an equivalent to sk_err in recvmmsg, though.
> >>
> >> Ack. Tracing on early exit due to null vlen in sendmmsg() is still missing;
> having this might help in debugging issue(s) at call site.
> >>
> >
> > Likewise in recvmmsg().
> >
>
> Yes, I'll simply remove the "vlan == 0" optimization.
>
> Jan
>
> --
> Siemens AG, Corporate Technology, CT RDA IOT SES-DE Corporate
> Competence Center Embedded Linux

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Re: [PATCH] rtdm: Do not return an error from send/recvmmsg if there are packets

[Jan Kiszka]

On 15.11.19 13:42, Lange Norbert wrote:
> Hello,
> 
> Just for consideration, If you can pass both error value and # of successfully sent packets out of the kernel function,
> perhaps you could return the # (if > 0) and still set errno in case of an (real) error?
> 
> It would be somewhat different to Linux, but that would not be the only difference (like theres no way to block until all msgs are sent/received).

I rather prefer finding and fixing what differentiates us from the kernel.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux