Re: [PATCH 1/6] maintenance: add get_random_minute()

On 8/7/2023 5:20 PM, Taylor Blau wrote:

On Mon, Aug 07, 2023 at 06:51:35PM +0000, Derrick Stolee via GitGitGadget wrote:

quoted

+	if (!random_initialized) {
+		srand((unsigned int)getpid());
+		random_initialized = 1;
+	}

I was wondering where else we call srand() within Git, and it looks like
the only other spot is in `lock_file_timeout()`.

I doubt it, but is there a chance that that code depends on only calling
srand() once? I think the answer is "no", since we only use rand()
within that function to generate a random-ish backoff period, so I think
the repeatability of it doesn't matter all that much.

The main point would be to avoid the cost of spinning up the number
generator, but there is potential for a bug if we run both initializers:
the lockfile would re-use the same filenames after the generator is
reset.

So I think this is kind of outside the scope of your series, but I
wonder if we should have a git_rand() that automatically initializes the
PRNG with the value of getpid()? Then multiple callers can grab random
values at will without reinitializing the PRNG.

I see you're moving ahead with removing the srand() from the lockfile code,
so I'll focus on creating a `git_rand()` that centralizes the use of
srand(), but won't touch the code in the lockfile so your patch applies
independently.

Thanks,
-Stolee