Re: [PATCH 1/2] run-command: Remove set_nonblocking

From: Stefan Beller <sbeller@google.com>
Date: Nov 5, 2015, 19:22 UTC
Message-ID: <CAGZ79kZgEtKoYqxa8+wj0PCJedW140CQAPX6XwEYib1W3fPhXw@mail.gmail.com>
In-Reply-To: <xmqqpozo5lqg.fsf@gitster.mtv.corp.google.com>

On Thu, Nov 5, 2015 at 10:45 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 11 quoted lines

> Stefan Beller <sbeller@google.com> writes:
>
>> strbuf_read_once can also operate on blocking file descriptors if we are
>> sure they are ready. The poll (2) command however makes sure this is the
>> case.
>>
>> Reading the manual for poll (2), there may be spurious returns indicating
>> readiness but that is for network sockets only. Pipes should be unaffected.
>
> Given the presence of "for example" in that bug section, I wouldn't
> say "only" or "should be unaffected".

Reading the documentation we are in agreement, that we expect no spurious returns, no?

Show 6 quoted lines

>
>> By having this patch, we rely on the correctness of poll to return
>> only pipes ready to read.
>
> We rely on two things.  One is for poll to return only pipes that are
> non-empty.  The other is for read from a non-empty pipe not to block.

That's what I meant with 'pipe being ready'.

Show 9 quoted lines

>
>>
>> This fixes compilation in Windows.
>>
>> Signed-off-by: Stefan Beller <sbeller@google.com>
>> ---
>
> Thanks.  Let's apply these fixes on sb/submodule-parallel-fetch,
> merge the result to 'next' and have people play with it.

Maybe the commit message was weakly crafted. Do you want me to resend?

Show 35 quoted lines

>
>>  run-command.c | 13 -------------
>>  1 file changed, 13 deletions(-)
>>
>> diff --git a/run-command.c b/run-command.c
>> index 0a3c24e..51d078c 100644
>> --- a/run-command.c
>> +++ b/run-command.c
>> @@ -1006,17 +1006,6 @@ static void pp_cleanup(struct parallel_processes *pp)
>>       sigchain_pop_common();
>>  }
>>
>> -static void set_nonblocking(int fd)
>> -{
>> -     int flags = fcntl(fd, F_GETFL);
>> -     if (flags < 0)
>> -             warning("Could not get file status flags, "
>> -                     "output will be degraded");
>> -     else if (fcntl(fd, F_SETFL, flags | O_NONBLOCK))
>> -             warning("Could not set file status flags, "
>> -                     "output will be degraded");
>> -}
>> -
>>  /* returns
>>   *  0 if a new task was started.
>>   *  1 if no new jobs was started (get_next_task ran out of work, non critical
>> @@ -1052,8 +1041,6 @@ static int pp_start_one(struct parallel_processes *pp)
>>               return code ? -1 : 1;
>>       }
>>
>> -     set_nonblocking(pp->children[i].process.err);
>> -
>>       pp->nr_processes++;
>>       pp->children[i].in_use = 1;
>>       pp->pfd[i].fd = pp->children[i].process.err;