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Subject: Re: [PATCH 3/3] Refactor atfork handlers
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
References: <1518008967-8310-1-git-send-email-adhemerval.zanella@linaro.org>
 <1518008967-8310-3-git-send-email-adhemerval.zanella@linaro.org>
 <c37a9fdc-08ea-af29-d8aa-2f96339d0df9@redhat.com>
 <d74735fd-bcd3-18b0-433b-14958ac29c05@linaro.org>
From: Florian Weimer <fweimer@redhat.com>
Message-ID: <88a58530-092d-4daa-1096-97a1bf8e08ff@redhat.com>
Date: Thu, 08 Feb 2018 11:26:00 -0000
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On 02/07/2018 06:16 PM, Adhemerval Zanella wrote:
> +  for (size_t i = 0; i < fork_handler_list_size (&fork_handlers);)
> +    {
> +      /* dynarray remove maintains element order, so update index iff there is
> +	 no removal.  */
> +      if (fork_handler_list_at (&fork_handlers, i)->dso_handle == dso_handle)
> +        fork_handler_list_remove (&fork_handlers, i);
> +      else
> +        i++;
> +    }

I thought a bit more about this.  Doesn't this lead to cubic run-time as 
DSOs are unloaded (quadratic run-time locally here, multiplied by the 
outer loop for unloading the DSOs)?

I think fork_handler_list_remove is the wrong abstraction here. 
Something like std::remove_if would be better, which moves each array 
element at most once even if multiple elements are removed during the 
scan.  Writing this generically in C is probably not worth the effort, 
so perhaps open-code that here?

Thanks,
Florian