From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-developers@cygwin.com
Subject: Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?
Date: Mon, 13 Sep 2021 08:54:31 +0900 [thread overview]
Message-ID: <20210913085431.8b13feaba276699fc3920a7b@nifty.ne.jp> (raw)
In-Reply-To: <dbf72463-dde5-f453-bf21-eb68c398a465@cornell.edu>
On Sun, 12 Sep 2021 17:46:47 -0400
Ken Brown wrote:
> On 9/12/2021 11:10 AM, Ken Brown wrote:
> > On 9/12/2021 7:04 AM, Takashi Yano wrote:
> >> On Sun, 12 Sep 2021 17:48:49 +0900
> >> Takashi Yano wrote:
> >>> On Sat, 11 Sep 2021 09:12:02 -0400
> >>> Ken Brown wrote:
> >>>> On 9/10/2021 10:35 PM, Takashi Yano wrote:
> >>>>> On Fri, 10 Sep 2021 22:17:21 -0400
> >>>>> Ken Brown wrote:
> >>>>>> On 9/10/2021 6:57 PM, Takashi Yano wrote:
> >>>>>>> On Fri, 10 Sep 2021 11:17:58 -0400
> >>>>>>> Ken Brown wrote:
> >>>>>>>> I've rerun your test with the latest version, and the test results are
> >>>>>>>> similar.
> >>>>>>>> I've also run a suite of fifo tests that I've accumulated, and they
> >>>>>>>> all pass
> >>>>>>>> also, so I pushed your patch.
> >>>>>>>>
> >>>>>>>> I think we're in pretty good shape now. The only detail remaining,
> >>>>>>>> AFAIK, is
> >>>>>>>> how to best avoid a deadlock if the pipe has been created by a non-Cygwin
> >>>>>>>> process. I've proposed a timeout, but maybe there's a better idea.
> >>>>>>>
> >>>>>>> I am not pretty sure what is the problem, but is not the following
> >>>>>>> patch enough?
> >>>>>>>
> >>>>>>> diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
> >>>>>>> index d309be2f7..13fba9a14 100644
> >>>>>>> --- a/winsup/cygwin/fhandler.h
> >>>>>>> +++ b/winsup/cygwin/fhandler.h
> >>>>>>> @@ -1205,6 +1205,7 @@ public:
> >>>>>>> select_record *select_except (select_stuff *);
> >>>>>>> char *get_proc_fd_name (char *buf);
> >>>>>>> int open (int flags, mode_t mode = 0);
> >>>>>>> + void open_setup (int flags);
> >>>>>>> void fixup_after_fork (HANDLE);
> >>>>>>> int dup (fhandler_base *child, int);
> >>>>>>> int close ();
> >>>>>>> diff --git a/winsup/cygwin/fhandler_pipe.cc b/winsup/cygwin/fhandler_pipe.cc
> >>>>>>> index 6994a5dce..d84e6ad84 100644
> >>>>>>> --- a/winsup/cygwin/fhandler_pipe.cc
> >>>>>>> +++ b/winsup/cygwin/fhandler_pipe.cc
> >>>>>>> @@ -191,6 +191,17 @@ out:
> >>>>>>> return 0;
> >>>>>>> }
> >>>>>>>
> >>>>>>> +void
> >>>>>>> +fhandler_pipe::open_setup (int flags)
> >>>>>>> +{
> >>>>>>> + fhandler_base::open_setup (flags);
> >>>>>>> + if (get_dev () == FH_PIPER && !read_mtx)
> >>>>>>> + {
> >>>>>>> + SECURITY_ATTRIBUTES *sa = sec_none_cloexec (flags);
> >>>>>>> + read_mtx = CreateMutexW (sa, FALSE, NULL);
> >>>>>>> + }
> >>>>>>> +}
> >>>>>>> +
> >>>>>>> off_t
> >>>>>>> fhandler_pipe::lseek (off_t offset, int whence)
> >>>>>>> {
> >>>>>>>
> >>>>>>>
> >>>>>>> AFAIK, another problem remaining is:
> >>>>>>>
> >>>>>>> On Mon, 6 Sep 2021 14:49:55 +0200
> >>>>>>> Corinna Vinschen wrote:
> >>>>>>>> - What about calling select for writing on pipes read by non-Cygwin
> >>>>>>>> processes? In that case, we still can't rely on WriteQuotaAvailable,
> >>>>>>>> just as before.
> >>>>>>
> >>>>>> This is the problem I was talking about. In this case the non-Cygwin process
> >>>>>> might have a large pending read, so that the Cygwin process calling select on
> >>>>>> the write side will see WriteQuotaAvailable == 0. This could lead to a
> >>>>>> deadlock
> >>>>>> with the Cygwin process waiting for write ready while the non-Cygwin
> >>>>>> process is
> >>>>>> blocked trying to read.
> >>>>>
> >>>>> Then, the above patch is for another issue.
> >>>>> The problem happes when:
> >>>>> 1) Start command prompt.
> >>>>> 2) Run 'echo AAAAAAAAAAAA | \cygwin64\bin\cat
> >>>>> This causes hang up in cat. In this case, pipe is created by cmd.exe.
> >>>>> Therefore, read_mtx is not created.
> >>>>
> >>>> Confirmed, and your patch fixes it. Maybe you should check for error in the
> >>>> call to CreateMutexW and print a debug message in that case.
> >>>>
> >>>>>> My suggestion is that we impose a timeout in this situation, after which
> >>>>>> select
> >>>>>> reports write ready.
> >>>>>
> >>>>> Keeping read handle in write pipe (Corinna's query_hdl) causes problem
> >>>>> that write side cannot detect close on read side.
> >>>>> Is it possible to open read handle temporally when pipe_data_available()
> >>>>> is called?
> >>>>
> >>>> That would be nice, but I have no idea how you could do that.
> >>>
> >>> Hmm. Then, what about PoC code attached? This returns to Corinna's
> >>> query_hdl, and counts read/write handles to detect closing reader side.
> >>>
> >>> If the number of read handles is equal to number of write handles,
> >>> only the pairs of write handle and query_hdl are alive. So, read pipe
> >>> supposed to be closed.
> >>>
> >>> This patch depends another patch I posted a few hours ago.
> >>
> >> Revised a bit.
> >
> > I don't see how this solves the problem. In the case we were worried about
> > where we have a non-Cygwin reader, the writer has no query_hdl, and you're just
> > always reporting write ready, aren't you? Or am I missing something?
>
> BTW, we could just decide that always reporting write ready in this corner case
> is acceptable. But then we could just do that without going back to query_hdl.
The various combination of cygwin and non-cygwin cases resuts in:
W P R: current, query_hdl
c c c: OK , OK
c c n: NG , OK
c n c: OK , OK
c n n: NG , select() always report write ready
where
W: Writer
P: Pipe
R: Reder
c: cygwin
n: non-cygwin
* Reder requests larger block than pipe size.
* Writer cannot be non-cygwin because we assume the case
that writer uses select().
--
Takashi Yano <takashi.yano@nifty.ne.jp>
next prev parent reply other threads:[~2021-09-12 23:54 UTC|newest]
Thread overview: 250+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <41A583E1-C8E7-42AB-9F24-EEC33A41EC60@house.org>
[not found] ` <20210825201845.07b6400b79dc5558a7761efe@nifty.ne.jp>
[not found] ` <f8106fe7-a2b8-d106-3061-4d888124f4b0@cornell.edu>
[not found] ` <20210826062934.54f2f2216021c095bb7ba13b@nifty.ne.jp>
[not found] ` <d0a8c57d-1ed1-6b4f-c6e7-cbe0e2ec8a1c@cornell.edu>
[not found] ` <3b560051-ab27-f392-ca4b-d1fd9b5733b0@cornell.edu>
[not found] ` <20210827202440.47706fc2fc07c5e9a1bc0047@nifty.ne.jp>
[not found] ` <4f2cb5f3-ce9c-c617-f65f-841a5eca096e@cornell.edu>
[not found] ` <20210828022111.91ef5b4ff24f6da9fadb489e@nifty.ne.jp>
[not found] ` <YSn3L0W1M527utK0@calimero.vinschen.de>
[not found] ` <20210828184102.f2206a8a9e5fe5cf24bf5e45@nifty.ne.jp>
[not found] ` <YSok0PoCQn2TPPrn@calimero.vinschen.de>
[not found] ` <20210829004346.c2f80469abc3a07fd4b2918d@nifty.ne.jp>
[not found] ` <e8caa02f-be85-33bc-3f09-347c1cdb0923@cornell.edu>
[not found] ` <20210829174124.0c1ae6c16a3e8da1f490abc7@nifty.ne.jp>
[not found] ` <6e9bb35e-6f4f-cf78-e515-549da487b5ef@cornell.edu>
2021-08-30 7:57 ` Corinna Vinschen
[not found] ` <20210829180729.48b4e877f773cb3980c5766d@nifty.ne.jp>
[not found] ` <789f056a-f164-d71d-1dc9-230f5a41846d@cornell.edu>
2021-08-30 8:27 ` Corinna Vinschen
2021-08-30 13:00 ` Corinna Vinschen
2021-08-30 13:20 ` Corinna Vinschen
2021-08-30 13:41 ` Ken Brown
2021-08-30 14:12 ` Corinna Vinschen
2021-08-30 14:52 ` Ken Brown
2021-08-30 15:15 ` Corinna Vinschen
[not found] ` <20210830043756.8aa0ada77db0bfbbe3889f62@nifty.ne.jp>
[not found] ` <47e5dd74-b940-f305-fd5a-c6c9d8f41305@cornell.edu>
2021-08-30 8:48 ` Corinna Vinschen
[not found] ` <c62d18df-ab7a-7233-62ee-29a8eced5353@cornell.edu>
[not found] ` <20210830091314.f9a2cb71794d0f68cdb5eba7@nifty.ne.jp>
[not found] ` <20210830092259.52f7d54fc3fa340738373af4@nifty.ne.jp>
[not found] ` <d217ef03-7858-5e22-0aa6-f0507eedd9da@cornell.edu>
[not found] ` <20210830170204.fa91eaf110f310f13b67abc3@nifty.ne.jp>
2021-08-30 10:20 ` Corinna Vinschen
2021-08-30 10:38 ` Corinna Vinschen
2021-08-30 12:04 ` Takashi Yano
2021-08-30 12:55 ` Corinna Vinschen
2021-08-30 13:31 ` Corinna Vinschen
2021-08-31 8:50 ` Takashi Yano
2021-08-30 13:51 ` Ken Brown
2021-08-30 15:00 ` Ken Brown
2021-08-30 15:19 ` Corinna Vinschen
2021-08-30 15:43 ` Ken Brown
2021-08-31 9:43 ` Corinna Vinschen
2021-08-31 8:52 ` Takashi Yano
2021-08-31 9:04 ` Corinna Vinschen
2021-08-31 11:05 ` Takashi Yano
2021-08-31 15:20 ` Corinna Vinschen
2021-09-01 2:39 ` Takashi Yano
2021-09-01 8:03 ` Corinna Vinschen
2021-09-01 8:13 ` Corinna Vinschen
2021-08-30 13:36 ` Ken Brown
2021-08-30 14:05 ` Corinna Vinschen
2021-08-30 15:53 ` Corinna Vinschen
2021-08-30 17:00 ` Corinna Vinschen
2021-08-30 17:11 ` Corinna Vinschen
2021-08-30 18:59 ` Ken Brown
2021-08-30 19:12 ` Ken Brown
2021-08-30 20:21 ` Corinna Vinschen
2021-08-30 20:14 ` Corinna Vinschen
2021-08-30 20:47 ` Ken Brown
2021-08-31 8:55 ` Takashi Yano
2021-08-31 9:08 ` Corinna Vinschen
2021-08-31 9:25 ` Takashi Yano
2021-08-31 10:05 ` Corinna Vinschen
2021-08-31 10:18 ` Corinna Vinschen
2021-08-31 11:45 ` Takashi Yano
2021-08-31 12:31 ` Takashi Yano
2021-08-31 15:08 ` Corinna Vinschen
2021-08-31 12:33 ` Ken Brown
2021-08-31 15:18 ` Corinna Vinschen
2021-08-31 15:27 ` Corinna Vinschen
2021-08-31 15:50 ` Corinna Vinschen
2021-08-31 16:19 ` Ken Brown
2021-08-31 16:38 ` Ken Brown
2021-08-31 17:30 ` Corinna Vinschen
2021-08-31 18:54 ` Ken Brown
2021-08-31 19:51 ` Corinna Vinschen
2021-08-31 23:02 ` Takashi Yano
2021-09-01 0:16 ` Takashi Yano
2021-09-01 8:07 ` Corinna Vinschen
2021-09-01 8:23 ` Takashi Yano
2021-09-01 8:46 ` Corinna Vinschen
2021-09-01 12:56 ` Ken Brown
2021-09-01 13:52 ` Corinna Vinschen
2021-09-01 23:02 ` Ken Brown
2021-09-02 8:17 ` Corinna Vinschen
2021-09-02 13:01 ` Ken Brown
2021-09-02 19:00 ` Corinna Vinschen
2021-09-02 19:34 ` Ken Brown
2021-09-02 19:35 ` Corinna Vinschen
2021-09-02 20:19 ` Ken Brown
2021-09-03 9:12 ` Corinna Vinschen
2021-09-03 19:00 ` Ken Brown
2021-09-03 19:53 ` Ken Brown
2021-09-03 19:54 ` Corinna Vinschen
2021-09-03 20:05 ` Ken Brown
2021-09-03 10:00 ` Takashi Yano
2021-09-03 10:13 ` Takashi Yano
2021-09-03 11:31 ` Corinna Vinschen
2021-09-03 11:41 ` Corinna Vinschen
2021-09-03 12:13 ` Ken Brown
2021-09-03 15:00 ` Corinna Vinschen
2021-09-03 15:14 ` Ken Brown
2021-09-03 15:17 ` Corinna Vinschen
2021-09-03 12:22 ` Takashi Yano
2021-09-03 13:27 ` Ken Brown
2021-09-03 15:37 ` Corinna Vinschen
2021-09-04 12:02 ` Takashi Yano
2021-09-04 12:37 ` Takashi Yano
2021-09-04 14:04 ` Ken Brown
2021-09-04 23:15 ` Takashi Yano
2021-09-05 13:40 ` Takashi Yano
2021-09-05 13:50 ` Takashi Yano
2021-09-05 18:47 ` Ken Brown
2021-09-05 19:42 ` Takashi Yano
2021-09-05 20:09 ` Takashi Yano
2021-09-05 20:27 ` Ken Brown
2021-09-06 8:13 ` Corinna Vinschen
2021-09-06 11:16 ` Takashi Yano
2021-09-06 12:49 ` Corinna Vinschen
2021-09-06 13:16 ` Takashi Yano
2021-09-06 16:08 ` Corinna Vinschen
2021-09-06 23:39 ` Takashi Yano
2021-09-07 9:14 ` Corinna Vinschen
2021-09-07 11:03 ` Takashi Yano
2021-09-07 16:14 ` Ken Brown
2021-09-07 18:26 ` Corinna Vinschen
2021-09-03 10:38 ` Takashi Yano
2021-09-08 11:32 ` Takashi Yano
2021-09-08 11:55 ` Corinna Vinschen
2021-09-08 12:33 ` Takashi Yano
2021-09-08 17:43 ` Ken Brown
2021-09-08 18:28 ` Corinna Vinschen
2021-09-02 8:15 ` Takashi Yano
2021-09-02 18:54 ` Corinna Vinschen
2021-09-07 3:26 ` Takashi Yano
2021-09-07 10:50 ` Takashi Yano
2021-09-08 0:07 ` Takashi Yano
2021-09-08 4:11 ` Takashi Yano
2021-09-08 9:01 ` Takashi Yano
2021-09-08 9:01 ` Corinna Vinschen
2021-09-08 9:26 ` Corinna Vinschen
2021-09-08 9:45 ` Takashi Yano
2021-09-08 10:04 ` Corinna Vinschen
2021-09-08 10:45 ` Takashi Yano
2021-09-08 10:51 ` Corinna Vinschen
2021-09-09 3:21 ` Takashi Yano
2021-09-09 9:37 ` Corinna Vinschen
2021-09-09 10:55 ` Takashi Yano
2021-09-09 11:41 ` Corinna Vinschen
2021-09-08 9:37 ` Takashi Yano
2021-09-09 3:41 ` Takashi Yano
2021-09-09 8:05 ` Takashi Yano
2021-09-09 12:19 ` Takashi Yano
2021-09-09 12:42 ` Takashi Yano
2021-09-09 21:53 ` Takashi Yano
2021-09-10 3:41 ` Takashi Yano
2021-09-10 10:57 ` Ken Brown
2021-09-10 15:17 ` Ken Brown
2021-09-10 15:26 ` Corinna Vinschen
2021-09-10 22:57 ` Takashi Yano
2021-09-11 2:17 ` Ken Brown
2021-09-11 2:35 ` Takashi Yano
2021-09-11 13:12 ` Ken Brown
2021-09-12 6:23 ` Takashi Yano
2021-09-12 14:39 ` Ken Brown
2021-09-13 9:11 ` Corinna Vinschen
2021-09-13 12:30 ` Ken Brown
2021-09-12 8:48 ` Takashi Yano
2021-09-12 11:04 ` Takashi Yano
2021-09-12 15:10 ` Ken Brown
2021-09-12 21:46 ` Ken Brown
2021-09-12 23:54 ` Takashi Yano [this message]
2021-09-13 2:19 ` Ken Brown
2021-09-13 8:40 ` Takashi Yano
2021-09-13 12:51 ` Ken Brown
2021-09-13 17:05 ` Ken Brown
2021-09-13 9:42 ` Corinna Vinschen
2021-09-13 13:03 ` Ken Brown
2021-09-13 18:39 ` Takashi Yano
2021-09-12 23:41 ` Takashi Yano
2021-09-13 17:42 ` Ken Brown
2021-09-13 18:54 ` Takashi Yano
2021-09-13 18:32 ` Corinna Vinschen
2021-09-13 19:37 ` Takashi Yano
2021-09-13 20:15 ` Corinna Vinschen
2021-09-14 8:07 ` Takashi Yano
2021-09-14 8:47 ` Corinna Vinschen
2021-09-14 12:38 ` Ken Brown
2021-09-14 14:15 ` Corinna Vinschen
2021-09-14 8:08 ` Takashi Yano
2021-09-14 9:03 ` Corinna Vinschen
2021-09-14 9:56 ` Takashi Yano
2021-09-14 10:19 ` Takashi Yano
2021-09-14 11:03 ` Corinna Vinschen
2021-09-14 12:05 ` Takashi Yano
2021-09-14 14:17 ` Corinna Vinschen
2021-09-14 22:14 ` Ken Brown
2021-09-15 0:21 ` Takashi Yano
2021-09-15 0:44 ` Takashi Yano
2021-09-15 0:59 ` Takashi Yano
2021-09-15 9:57 ` Corinna Vinschen
2021-09-15 10:48 ` Takashi Yano
2021-09-15 10:58 ` Takashi Yano
2021-09-15 11:34 ` Corinna Vinschen
2021-09-15 11:40 ` Corinna Vinschen
2021-09-15 11:13 ` Corinna Vinschen
2021-09-15 11:41 ` Ken Brown
2021-09-15 11:49 ` Corinna Vinschen
2021-09-15 11:54 ` Takashi Yano
2021-09-15 12:20 ` Corinna Vinschen
2021-09-15 13:04 ` Takashi Yano
2021-09-15 13:42 ` Corinna Vinschen
2021-09-15 16:22 ` Ken Brown
2021-09-15 17:09 ` Ken Brown
2021-09-16 0:22 ` Takashi Yano
2021-09-16 2:28 ` Ken Brown
2021-09-16 9:09 ` Takashi Yano
2021-09-16 13:02 ` Takashi Yano
2021-09-16 13:25 ` Corinna Vinschen
2021-09-16 14:27 ` Takashi Yano
2021-09-16 15:01 ` Corinna Vinschen
2021-09-16 15:46 ` Ken Brown
2021-09-16 16:02 ` Ken Brown
2021-09-16 19:42 ` Takashi Yano
2021-09-16 20:28 ` Ken Brown
2021-09-16 19:48 ` Ken Brown
2021-09-16 20:01 ` Takashi Yano
2021-09-17 2:25 ` Ken Brown
2021-09-17 8:31 ` Takashi Yano
2021-09-17 11:16 ` Ken Brown
2021-09-17 16:23 ` Takashi Yano
2021-09-17 17:08 ` Ken Brown
2021-09-17 17:39 ` Jon Turney
2021-09-17 17:43 ` Takashi Yano
2021-09-17 19:53 ` Ken Brown
2021-09-18 1:30 ` Takashi Yano
2021-09-18 2:07 ` Ken Brown
2021-09-18 2:10 ` Ken Brown
2021-09-18 8:03 ` Takashi Yano
2021-09-18 11:12 ` Ken Brown
2021-09-18 11:35 ` Takashi Yano
2021-09-18 14:11 ` Jon Turney
2021-09-18 13:44 ` Ken Brown
2021-09-19 1:31 ` Takashi Yano
2021-09-19 14:35 ` Ken Brown
2021-09-20 9:29 ` Takashi Yano
2021-09-16 0:13 ` Takashi Yano
2021-09-16 2:26 ` Ken Brown
2021-09-13 9:07 ` Corinna Vinschen
2021-09-20 12:52 ` Takashi Yano
2021-09-20 19:14 ` Ken Brown
2021-09-20 21:09 ` Ken Brown
2021-09-20 21:21 ` Ken Brown
2021-09-20 21:27 ` Takashi Yano
2021-09-20 21:39 ` Ken Brown
2021-09-20 22:16 ` Takashi Yano
2021-09-20 22:46 ` Ken Brown
2021-09-20 22:50 ` Ken Brown
2021-09-20 23:22 ` Takashi Yano
2021-09-21 8:30 ` Takashi Yano
2021-09-21 9:26 ` Mark Geisert
2021-09-21 10:10 ` Takashi Yano
2021-09-21 21:10 ` Mark Geisert
2021-09-21 13:31 ` Ken Brown
2021-09-21 15:36 ` Takashi Yano
2021-09-21 18:51 ` Ken Brown
2021-09-23 8:26 ` Takashi Yano
2021-09-23 13:03 ` Ken Brown
2021-09-23 15:03 ` Takashi Yano
2021-09-23 16:29 ` Ken Brown
2021-10-18 10:51 ` Corinna Vinschen
2021-10-18 12:02 ` Takashi Yano
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