| Message ID | 76e7698d-890b-d14d-fa34-da5dd7dd13d8@sberdevices.ru (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [RFC,v1] vsock: check error queue to set EPOLLERR | expand |
On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote: >EPOLLERR must be set not only when there is error on the socket, but also >when error queue of it is not empty (may be it contains some control >messages). Without this patch 'poll()' won't detect data in error queue. Do you have a reproducer? >This patch is based on 'tcp_poll()'. LGTM but we should add a Fixes tag. It's not clear to me whether the problem depends on when we switched to using sk_buff or was pre-existing. Do you have any idea when we introduced this issue? Thanks, Stefano > >Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >--- > net/vmw_vsock/af_vsock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >index 19aea7cba26e..b5e51ef4a74c 100644 >--- a/net/vmw_vsock/af_vsock.c >+++ b/net/vmw_vsock/af_vsock.c >@@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, > poll_wait(file, sk_sleep(sk), wait); > mask = 0; > >- if (sk->sk_err) >+ if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) > /* Signify that there has been an error on this socket. */ > mask |= EPOLLERR; > >-- >2.25.1 >
Hello! On 02.03.2023 13:06, Stefano Garzarella wrote: > On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote: >> EPOLLERR must be set not only when there is error on the socket, but also >> when error queue of it is not empty (may be it contains some control >> messages). Without this patch 'poll()' won't detect data in error queue. > > Do you have a reproducer? > Dedicated reproducer - no:) To reproduce this issue, i used last MSG_ZEROCOPY patches. Completion was inserted to error queue, and 'poll()' didn't report about it. That was the reason, why this patch was included to MSG_ZEROCOPY patchset. But also i think it is better to reduce number of patches in it(i'm working on v2), so it is good to handle this patch separately. May be one way to reproduce it is use SO_TIMESTAMP(time info about skbuff will be queued to the error queue). IIUC this feature is implemented at socket layer and may work in vsock (but i'm not sure). Ok, i'll check it and try to implement reproducer. IIUC, for future, policy for fixes is "for each fix implement reproducer in vsock_test"? >> This patch is based on 'tcp_poll()'. > > LGTM but we should add a Fixes tag. > It's not clear to me whether the problem depends on when we switched to using sk_buff or was pre-existing. > > Do you have any idea when we introduced this issue? git blame shows, that this code exists since first commit to vsock: commit d021c344051af91f42c5ba9fdedc176740cbd238 Author: Andy King <acking@vmware.com> Date: Wed Feb 6 14:23:56 2013 +0000 VSOCK: Introduce VM Sockets For TCP same logic was added by: commit 4ed2d765dfaccff5ebdac68e2064b59125033a3b Author: Willem de Bruijn <willemb@google.com> Date: Mon Aug 4 22:11:49 2014 -0400 net-timestamp: TCP timestamping > > Thanks, > Stefano > Thanks Arseniy >> >> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >> --- >> net/vmw_vsock/af_vsock.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >> index 19aea7cba26e..b5e51ef4a74c 100644 >> --- a/net/vmw_vsock/af_vsock.c >> +++ b/net/vmw_vsock/af_vsock.c >> @@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, >> poll_wait(file, sk_sleep(sk), wait); >> mask = 0; >> >> - if (sk->sk_err) >> + if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) >> /* Signify that there has been an error on this socket. */ >> mask |= EPOLLERR; >> >> -- >> 2.25.1 >> >
On Thu, Mar 02, 2023 at 02:41:29PM +0300, Arseniy Krasnov wrote: >Hello! > >On 02.03.2023 13:06, Stefano Garzarella wrote: >> On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote: >>> EPOLLERR must be set not only when there is error on the socket, but also >>> when error queue of it is not empty (may be it contains some control >>> messages). Without this patch 'poll()' won't detect data in error queue. >> >> Do you have a reproducer? >> >Dedicated reproducer - no:) >To reproduce this issue, i used last MSG_ZEROCOPY patches. Completion was inserted to >error queue, and 'poll()' didn't report about it. That was the reason, why this patch >was included to MSG_ZEROCOPY patchset. But also i think it is better to reduce number >of patches in it(i'm working on v2), so it is good to handle this patch separately. Yep, absolutely! >May be one way to reproduce it is use SO_TIMESTAMP(time info about skbuff will be queued >to the error queue). IIUC this feature is implemented at socket layer and may work in >vsock (but i'm not sure). Ok, i'll check it and try to implement reproducer. > >IIUC, for future, policy for fixes is "for each fix implement reproducer in vsock_test"? Nope, but for each fix we should have a Fixes tag. Usually we use vsock_test to check regressions on features and also the behaviour of different transports. My question was more about whether this problem was there before supporting sk_buff or not, to figure out which Fixes tag to use. > >>> This patch is based on 'tcp_poll()'. >> >> LGTM but we should add a Fixes tag. >> It's not clear to me whether the problem depends on when we switched to using sk_buff or was pre-existing. >> >> Do you have any idea when we introduced this issue? >git blame shows, that this code exists since first commit to vsock: Okay, but did we use sk_error_queue before supporting sk_buff? Anyway, if we are not sure I think we can use the following Fixes tag, I don't see any issue if we backport this patch also before supporting sk_buff. Thanks, Stefano > >commit d021c344051af91f42c5ba9fdedc176740cbd238 >Author: Andy King <acking@vmware.com> >Date: Wed Feb 6 14:23:56 2013 +0000 > > VSOCK: Introduce VM Sockets > >For TCP same logic was added by: > >commit 4ed2d765dfaccff5ebdac68e2064b59125033a3b >Author: Willem de Bruijn <willemb@google.com> >Date: Mon Aug 4 22:11:49 2014 -0400 > > net-timestamp: TCP timestamping > > >> >> Thanks, >> Stefano >> > >Thanks Arseniy > >>> >>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >>> --- >>> net/vmw_vsock/af_vsock.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >>> index 19aea7cba26e..b5e51ef4a74c 100644 >>> --- a/net/vmw_vsock/af_vsock.c >>> +++ b/net/vmw_vsock/af_vsock.c >>> @@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, >>> poll_wait(file, sk_sleep(sk), wait); >>> mask = 0; >>> >>> - if (sk->sk_err) >>> + if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) >>> /* Signify that there has been an error on this socket. */ >>> mask |= EPOLLERR; >>> >>> -- >>> 2.25.1 >>> >> >
On 02.03.2023 16:38, Stefano Garzarella wrote: > On Thu, Mar 02, 2023 at 02:41:29PM +0300, Arseniy Krasnov wrote: >> Hello! >> >> On 02.03.2023 13:06, Stefano Garzarella wrote: >>> On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote: >>>> EPOLLERR must be set not only when there is error on the socket, but also >>>> when error queue of it is not empty (may be it contains some control >>>> messages). Without this patch 'poll()' won't detect data in error queue. >>> >>> Do you have a reproducer? >>> >> Dedicated reproducer - no:) >> To reproduce this issue, i used last MSG_ZEROCOPY patches. Completion was inserted to >> error queue, and 'poll()' didn't report about it. That was the reason, why this patch >> was included to MSG_ZEROCOPY patchset. But also i think it is better to reduce number >> of patches in it(i'm working on v2), so it is good to handle this patch separately. > > Yep, absolutely! > >> May be one way to reproduce it is use SO_TIMESTAMP(time info about skbuff will be queued >> to the error queue). IIUC this feature is implemented at socket layer and may work in >> vsock (but i'm not sure). Ok, i'll check it and try to implement reproducer. >> >> IIUC, for future, policy for fixes is "for each fix implement reproducer in vsock_test"? > > Nope, but for each fix we should have a Fixes tag. > > Usually we use vsock_test to check regressions on features and also the > behaviour of different transports. > My question was more about whether this problem was there before > supporting sk_buff or not, to figure out which Fixes tag to use. > Ok i see >> >>>> This patch is based on 'tcp_poll()'. >>> >>> LGTM but we should add a Fixes tag. >>> It's not clear to me whether the problem depends on when we switched to using sk_buff or was pre-existing. >>> >>> Do you have any idea when we introduced this issue? >> git blame shows, that this code exists since first commit to vsock: > > Okay, but did we use sk_error_queue before supporting sk_buff? > No I think, sk_error_queue was unavailable to user(and still unavailable today), because we don't have check for MSG_ERRQUEUE flag in recv logic in af_vsock.c (i've added it in MSG_ZEROCOPY). So even if some subsystem of the kernel inserts skb to sk_error_queue in AF_VSOCK case, user won't dequeue it. > Anyway, if we are not sure I think we can use the following Fixes tag, > I don't see any issue if we backport this patch also before supporting > sk_buff. > Ok, i'll try to prepare reproducer(may be in vsock_test) and add Fixes tag with the commit "VSOCK: Introduce VM Sockets." Thanks, Arseniy > Thanks, > Stefano > >> >> commit d021c344051af91f42c5ba9fdedc176740cbd238 >> Author: Andy King <acking@vmware.com> >> Date: Wed Feb 6 14:23:56 2013 +0000 >> >> VSOCK: Introduce VM Sockets >> >> For TCP same logic was added by: >> >> commit 4ed2d765dfaccff5ebdac68e2064b59125033a3b >> Author: Willem de Bruijn <willemb@google.com> >> Date: Mon Aug 4 22:11:49 2014 -0400 >> >> net-timestamp: TCP timestamping >> >> >>> >>> Thanks, >>> Stefano >>> >> >> Thanks Arseniy >> >>>> >>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >>>> --- >>>> net/vmw_vsock/af_vsock.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >>>> index 19aea7cba26e..b5e51ef4a74c 100644 >>>> --- a/net/vmw_vsock/af_vsock.c >>>> +++ b/net/vmw_vsock/af_vsock.c >>>> @@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, >>>> poll_wait(file, sk_sleep(sk), wait); >>>> mask = 0; >>>> >>>> - if (sk->sk_err) >>>> + if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) >>>> /* Signify that there has been an error on this socket. */ >>>> mask |= EPOLLERR; >>>> >>>> -- >>>> 2.25.1 >>>> >>> >> >
On 02.03.2023 18:06, Arseniy Krasnov wrote: > > > On 02.03.2023 16:38, Stefano Garzarella wrote: >> On Thu, Mar 02, 2023 at 02:41:29PM +0300, Arseniy Krasnov wrote: >>> Hello! >>> >>> On 02.03.2023 13:06, Stefano Garzarella wrote: >>>> On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote: >>>>> EPOLLERR must be set not only when there is error on the socket, but also >>>>> when error queue of it is not empty (may be it contains some control >>>>> messages). Without this patch 'poll()' won't detect data in error queue. >>>> >>>> Do you have a reproducer? >>>> >>> Dedicated reproducer - no:) >>> To reproduce this issue, i used last MSG_ZEROCOPY patches. Completion was inserted to >>> error queue, and 'poll()' didn't report about it. That was the reason, why this patch >>> was included to MSG_ZEROCOPY patchset. But also i think it is better to reduce number >>> of patches in it(i'm working on v2), so it is good to handle this patch separately. >> >> Yep, absolutely! >> >>> May be one way to reproduce it is use SO_TIMESTAMP(time info about skbuff will be queued >>> to the error queue). IIUC this feature is implemented at socket layer and may work in >>> vsock (but i'm not sure). Ok, i'll check it and try to implement reproducer. >>> >>> IIUC, for future, policy for fixes is "for each fix implement reproducer in vsock_test"? >> >> Nope, but for each fix we should have a Fixes tag. >> >> Usually we use vsock_test to check regressions on features and also the >> behaviour of different transports. >> My question was more about whether this problem was there before >> supporting sk_buff or not, to figure out which Fixes tag to use. >> > Ok i see >>> >>>>> This patch is based on 'tcp_poll()'. >>>> >>>> LGTM but we should add a Fixes tag. >>>> It's not clear to me whether the problem depends on when we switched to using sk_buff or was pre-existing. >>>> >>>> Do you have any idea when we introduced this issue? >>> git blame shows, that this code exists since first commit to vsock: >> >> Okay, but did we use sk_error_queue before supporting sk_buff? >> > No I think, sk_error_queue was unavailable to user(and still unavailable today), > because we don't have check for MSG_ERRQUEUE flag in recv logic in af_vsock.c > (i've added it in MSG_ZEROCOPY). So even if some subsystem of the kernel inserts > skb to sk_error_queue in AF_VSOCK case, user won't dequeue it. > >> Anyway, if we are not sure I think we can use the following Fixes tag, >> I don't see any issue if we backport this patch also before supporting >> sk_buff. >> > Ok, i'll try to prepare reproducer(may be in vsock_test) and add Fixes tag with the > commit "VSOCK: Introduce VM Sockets." Hm, seems there is no way to reproduce it with AF_VSOCK in the current kernel: 1) I can't find test case how to use sk_error_queue(SO_TIMESTAMPXXX doesn't work on vsock - web says that it depends on NIC driver). And i don't see any generic socket layer features which uses sk_error_queue. 2) Anyway, as i mentioned above - user can't read data from sk_error_queue, because MSG_ERRQUEUE flag is not handled in af_vsock.c. So i'll resend this patch in MSG_ZEROCOPY v2 patchset - in this case, new MSG_ZEROCOPY logic will use this patch: it will be the "reproducer" Thanks, Arseniy > > Thanks, Arseniy >> Thanks, >> Stefano >> >>> >>> commit d021c344051af91f42c5ba9fdedc176740cbd238 >>> Author: Andy King <acking@vmware.com> >>> Date: Wed Feb 6 14:23:56 2013 +0000 >>> >>> VSOCK: Introduce VM Sockets >>> >>> For TCP same logic was added by: >>> >>> commit 4ed2d765dfaccff5ebdac68e2064b59125033a3b >>> Author: Willem de Bruijn <willemb@google.com> >>> Date: Mon Aug 4 22:11:49 2014 -0400 >>> >>> net-timestamp: TCP timestamping >>> >>> >>>> >>>> Thanks, >>>> Stefano >>>> >>> >>> Thanks Arseniy >>> >>>>> >>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >>>>> --- >>>>> net/vmw_vsock/af_vsock.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >>>>> index 19aea7cba26e..b5e51ef4a74c 100644 >>>>> --- a/net/vmw_vsock/af_vsock.c >>>>> +++ b/net/vmw_vsock/af_vsock.c >>>>> @@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, >>>>> poll_wait(file, sk_sleep(sk), wait); >>>>> mask = 0; >>>>> >>>>> - if (sk->sk_err) >>>>> + if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) >>>>> /* Signify that there has been an error on this socket. */ >>>>> mask |= EPOLLERR; >>>>> >>>>> -- >>>>> 2.25.1 >>>>> >>>> >>> >>
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 19aea7cba26e..b5e51ef4a74c 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, poll_wait(file, sk_sleep(sk), wait); mask = 0; - if (sk->sk_err) + if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) /* Signify that there has been an error on this socket. */ mask |= EPOLLERR;
EPOLLERR must be set not only when there is error on the socket, but also when error queue of it is not empty (may be it contains some control messages). Without this patch 'poll()' won't detect data in error queue. This patch is based on 'tcp_poll()'. Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> --- net/vmw_vsock/af_vsock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)