Looking at the Linux stack trace, the culprit seems the next-to-last line:
-------------
fcntl(3, F_SETFL, O_RDONLY) = 0
read(3, <hangs here>
-------------
i.e. at least on Linux the O_NONBLOCK bit gets cleared immediately before
the read()
On Thursday, January 25, 2018 at 12:00:01 PM UTC+1, Max wrote:
>
> I tried on Linux/amd64 (debian testing, kernel 4.14.0-2-amd64) and it's
> broken too:
>
> * go 1.9.3 + syscall.SetNonblock : hangs in syscall.Read()
> * go 1.9.3 + unix.SetNonblock : hangs in syscall.Read()
> * go 1.9.2 + syscall.SetNonblock : hangs in syscall.Read()
> * go 1.9.2 + unix.SetNonblock : hangs in syscall.Read()
>
> the relevant strace(1) fragment is:
>
> -----------------------------------
> pipe2([3, 4], O_CLOEXEC) = 0
> epoll_create1(EPOLL_CLOEXEC) = 5
> epoll_ctl(5, EPOLL_CTL_ADD, 3, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET,
> {u32=2231488256, u64=140400417427200}}) = 0
> fcntl(3, F_GETFL) = 0 (flags O_RDONLY)
> fcntl(3, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
> epoll_ctl(5, EPOLL_CTL_ADD, 4, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET,
> {u32=2231488064, u64=140400417427008}}) = 0
> fcntl(4, F_GETFL) = 0x1 (flags O_WRONLY)
> fcntl(4, F_SETFL, O_WRONLY|O_NONBLOCK) = 0
> fcntl(3, F_GETFL) = 0x800 (flags O_RDONLY|O_NONBLOCK)
> fcntl(3, F_SETFL, O_RDONLY) = 0
> fcntl(3, F_GETFL) = 0 (flags O_RDONLY)
> fcntl(3, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
> write(1, "Read START\n", 11Read START
> ) = 11
> fcntl(3, F_GETFL) = 0x800 (flags O_RDONLY|O_NONBLOCK)
> fcntl(3, F_SETFL, O_RDONLY) = 0
> read(3,
> <hangs here>
> -----------------------------------
>
> I hope this helps.
>
> David, did you already report the bug on
> https://github.com/golang/go/issues ?
> I can add the details above on the bug report too.
>
> Regards,
>
> Max
>
> On Thursday, January 25, 2018 at 11:03:47 AM UTC+1, Steven Hartland wrote:
>>
>> I checked this on FreeBSD and it still works, so seems like it could be a
>> macOS specific issue.
>>
>> You should raise a bug here:
>> https://github.com/golang/go/issues
>>
>> It would be good to try and identify the go version which it first broke
>> in too, as that will be helpful in identifying the change which cause the
>> regression.
>>
>> Regards
>> Steve
>>
>> On 25/01/2018 04:06, Dave Keck wrote:
>>
>> Hey all, this program exits (as expected) when run with macOS 10.12.6 +
>> Go 1.8.6, but it deadlocks when run with Go 1.9.3:
>>
>> https://play.golang.org/p/Dw_ND9gkgPm
>>
>> The same behavior is observed when using unix.SetNonblock instead of
>> syscall.SetNonblock.
>>
>> It appears that the SetNonblock() functions don't have an effect in Go
>> 1.9.3. Is this a known issue?
>>
>> Thanks!
>> David
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