Re: [PATCH] hashmap: add API to disable item counting when threaded

[Jonathan Nieder <jrnieder@gmail.com>]

Hi,

Johannes Schindelin wrote:
> On Wed, 30 Aug 2017, Jeff Hostetler wrote:

>> This is to address concerns raised by ThreadSanitizer on the mailing
>> list about threaded unprotected R/W access to map.size with my previous
>> "disallow rehash" change (0607e10009ee4e37cb49b4cec8d28a9dda1656a4).

Nice!

What does the message from TSan look like?  (The full message doesn't
need to go in the commit message, but a snippet can help.)  How can I
reproduce it?


>> See:
>> https://public-inbox.org/git/adb37b70139fd1e2bac18bfd22c8b96683ae18eb.1502780344.git.martin.agren@gmail.com/
>>
>> Add API to hashmap to disable item counting and to disable automatic
>> rehashing.  Also include APIs to re-enable item counting and automatica
>> rehashing.
>>
>> When item counting is disabled, the map.size field is invalid.  So to
>> prevent accidents, the field has been renamed and an accessor function
>> hashmap_get_size() has been added.  All direct references to this field
>> have been been updated.  And the name of the field changed to
>> map.private_size to communicate thie.
>>
>> Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
>> ---
>
> The Git contribution process forces me to point out lines longer than 80
> columns. I wish there was already an automated tool to fix that, but we
> (as in "the core Git developers") have not yet managed to agree on one. So
> I'll have to ask you to identify and fix them manually.

I *think* (but am not sure) that there is an implied bug report in this
comment, but I am not sure what that bug report is and how I can help
with it!  If you have a link to an issue tracker, thread, wiki page, or
other pointer where I can learn more, then that might help me.

Have you experimented with the patches in Junio's branch
bw/git-clang-format?

[...]
>> +	/* TODO Consider counting them and returning that. */
>
> I'd rather not. If counting is disabled, it is disabled.
>
>> +	die("hashmap_get_size: size not set");
>
> Before anybody can ask for this message to be wrapped in _(...) to be
> translateable, let me suggest instead to add the prefix "BUG: ".

Nowadays (since v2.13.2~26^2~3, 2017-05-12), there is a BUG() function
that you can use in place of die():

	BUG("hashmap_get_size: size not set");

Thanks and hope that helps,
Jonathan