Re: What's cooking in git.git (Apr 2014, #03; Fri, 11)

> Ramsay Jones <ramsay@ramsay1.demon.co.uk> writes:
>
>> On 11/04/14 23:22, Junio C Hamano wrote:
>> [...]
>>> [New Topics]
>>>
>>> * nd/index-pack-one-fd-per-thread (2014-04-09) 1 commit
>>>  - index-pack: work around thread-unsafe pread()
>>>
>>>  Enable threaded index-pack on platforms without thread-unsafe
>>>  pread() emulation.
>>>
>>>  Will merge to 'next' and keep it there for the remainder of the cycle.
>>
>> The commit message for commit 512ebe5d ("index-pack: work around
>> thread-unsafe pread()", 25-03-2014) is a little misleading.
>
> OK.  Can we have a concrete alternative?
>
>     Multi-threaing of index-pack was disabled with c0f8654
>     (index-pack: Disable threading on cygwin - 2012-06-26), because
>     pread() implementations for Cygwin and MSYS were not thread
>     safe.  Recent Cygwin does offer usable pread() and we enabled
>     multi-threading with 103d530f (Cygwin 1.7 has thread-safe pread,
>     2013-07-19).
>
>     Work around this problem on platforms with a thread-unsafe
>     pread() emulation by opening one file handle per thread; it
>     would prevent parallel pread() on different file handles from
>     stepping on each other.
>
>     Also remove NO_THREAD_SAFE_PREAD that was introduced in c0f8654
>     because it's no longer used anywhere.
>
>     This workaround is unconditional, even for platforms with
>     thread-safe pread() because the overhead is small (a couple file
>     handles more) and not worth fragmenting the code.
>