From: Ken Brown <kbrown@cornell.edu>
To: cygwin@cygwin.com
Subject: Re: mmap failure [was: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?]
Date: Tue, 7 Sep 2021 12:28:30 -0400 [thread overview]
Message-ID: <3bb3814c-0584-c918-6710-f71c7abfbcc5@cornell.edu> (raw)
In-Reply-To: <742331ee-4d9f-e86f-9314-c85b5f0cbfa8@SystematicSw.ab.ca>
On 9/6/2021 11:34 PM, Brian Inglis wrote:
> On 2021-09-06 15:24, Ken Brown via Cygwin wrote:
>> On 9/6/2021 4:54 PM, Peter Dons Tychsen wrote:
>>> Hi there,
>>>
>>> On Mon, 2021-09-06 at 14:40 -0400, Ken Brown via Cygwin wrote:
>>>>> No, wait. I get what you say. The optimzation settings of the test
>>>>> case should have no influence on the code inside the DLL. That
>>>>> doesn't
>>>>> make sense for sure. However, I ran the testcase under GDB, I could
>>>>> reproduce the issue, and I could fix it by setting mmap_ext.Reserved
>>>>> = 0;
>>>>> Go figure!
>>>>
>>>> I don't get it, but I can confirm that the problem is fixed.
>>>
>>> That sounds a bit like a voodoo fix, that could quickly regress again.
>>>
>>> Here is my 2 cents:
>>>
>>> Currently the mmap_ext structure is setup like this:
>>>
>>> 215 MEM_EXTENDED_PARAMETER mmap_ext = {
>>> 216 .Type = MemExtendedParameterAddressRequirements,
>>> 217 .Pointer = (PVOID) &mmap_req
>>> 218 };
>>>
>>> This means that all other entries in the struct are zero at
>>> initialization as described here:
>>> https://en.cppreference.com/w/c/language/struct_initialization
>>>
>>> So if you set "mmap_ext.Reserved = 0" again after that its a double
>>> failure.
>>
>> You're looking at the wrong source code. The bug didn't occur until the code
>> was changed to do the following:
>>
>> /* g++ 11.2 workaround: don't use initializer */
>> MEM_EXTENDED_PARAMETER mmap_ext;
>> mmap_ext.Type = MemExtendedParameterAddressRequirements;
>> mmap_ext.Pointer = (PVOID) &mmap_req;
>>
>> This left mmap_ext.Reserved uninitialized, which Corinna has now fixed.
>
> With undocumented structure member initialization an issue, maybe better to
> future proof using e.g.
>
> MEM_EXTENDED_PARAMETER mmap_ext = { 0 }; // or memset or bzero
I don't see what this would accomplish. We're already initializing every member
after Corinna's last patch.
Ken
next prev parent reply other threads:[~2021-09-07 16:28 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 19:49 cygrunsrv + sshd + rsync = 20 times too slow -- throttled? Chris Roehrig
2021-08-24 23:43 ` Mark Geisert
2021-08-25 0:35 ` Chris Roehrig
2021-08-25 2:12 ` Chris Roehrig
2021-08-25 2:02 ` NightStrike
2021-08-25 3:20 ` Mark Geisert
2021-08-25 17:24 ` Chris Roehrig
2021-08-25 11:18 ` Takashi Yano
2021-08-25 17:31 ` Chris Roehrig
2021-08-25 17:52 ` Ken Brown
2021-08-25 18:18 ` Chris Roehrig
2021-08-25 18:51 ` Chris Roehrig
2021-08-26 15:44 ` Ken Brown
2021-08-25 20:33 ` Mario Emmenlauer
2021-08-26 15:47 ` Ken Brown
2021-08-25 21:29 ` Takashi Yano
2021-08-26 15:56 ` Ken Brown
2021-08-26 22:18 ` Ken Brown
2021-08-27 11:24 ` Takashi Yano
2021-08-27 16:00 ` Ken Brown
2021-08-27 17:21 ` Takashi Yano
2021-08-28 2:00 ` Takashi Yano
2021-08-28 3:03 ` Takashi Yano
2021-08-28 8:43 ` Corinna Vinschen
2021-08-28 9:41 ` Takashi Yano
2021-08-28 11:58 ` Corinna Vinschen
2021-08-28 15:43 ` Takashi Yano
2021-08-28 20:55 ` Ken Brown
2021-08-29 8:41 ` Takashi Yano
2021-08-29 22:42 ` Ken Brown
2021-08-29 10:27 ` Corinna Vinschen
2021-08-29 9:07 ` Takashi Yano
2021-08-29 15:57 ` Ken Brown
2021-08-29 19:24 ` Chris Roehrig
2021-08-29 22:24 ` Ken Brown
2021-08-30 23:58 ` Chris Roehrig
2021-08-31 19:05 ` Ken Brown
2021-08-31 19:53 ` Chris Roehrig
2021-08-31 20:23 ` Chris Roehrig
2021-08-31 21:29 ` Brian Inglis
2021-09-01 21:11 ` Chris Roehrig
2021-09-02 15:25 ` Ken Brown
2021-09-02 19:03 ` Chris Roehrig
2021-09-03 17:26 ` Ken Brown
2021-09-03 19:55 ` Corinna Vinschen
2021-09-03 20:59 ` Chris Roehrig
2021-09-04 8:32 ` Achim Gratz
2021-09-04 16:45 ` Brian Inglis
2021-09-05 8:18 ` Achim Gratz
2021-09-05 15:11 ` Brian Inglis
2021-09-06 10:42 ` Achim Gratz
2021-09-04 22:37 ` mmap failure [was: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?] Ken Brown
2021-09-04 22:54 ` Ken Brown
2021-09-04 22:58 ` Ken Brown
2021-09-05 0:04 ` Ken Brown
2021-09-05 13:24 ` Ken Brown
2021-09-06 15:32 ` Corinna Vinschen
2021-09-06 17:12 ` Ken Brown
2021-09-06 17:38 ` Ken Brown
2021-09-06 17:43 ` Eliot Moss
2021-09-06 17:59 ` Corinna Vinschen
2021-09-06 18:07 ` Corinna Vinschen
2021-09-06 18:40 ` Ken Brown
2021-09-06 20:52 ` Peter Dons Tychsen
2021-09-06 20:54 ` Peter Dons Tychsen
2021-09-06 21:24 ` Ken Brown
2021-09-06 21:31 ` Ken Brown
2021-09-07 3:34 ` Brian Inglis
2021-09-07 16:28 ` Ken Brown [this message]
2021-09-07 21:52 ` Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2021-09-07 22:44 ` Ken Brown
2021-09-08 6:14 ` Sam Edge
2021-09-08 8:18 ` Corinna Vinschen
2021-09-07 21:41 ` Peter Dons Tychsen
2021-09-04 23:18 ` Brian Inglis
2021-08-29 19:37 ` cygrunsrv + sshd + rsync = 20 times too slow -- throttled? Takashi Yano
2021-08-29 21:09 ` Ken Brown
2021-08-29 21:04 ` Ken Brown
2021-08-30 0:13 ` Takashi Yano
2021-08-30 0:22 ` Takashi Yano
2021-08-30 2:15 ` Ken Brown
2021-08-30 8:02 ` Takashi Yano
2021-08-28 15:17 ` Ken Brown
2021-09-16 22:00 ` Keith Christian
2021-09-16 22:48 ` Ken Brown
2021-09-16 22:58 ` Keith Christian
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