Reviewed-by: Benoît Canet <ben...@scylladb.com>
On Sun, Aug 28, 2016 at 3:02 PM, Nadav Har'El <n...@scylladb.com> wrote:
> Implement pthread_key_delete().
>
> Currently, it will not mark the key available for re-use.
> The danger in allowing re-use is that if we leave data with that key (the
> pthread_key_delete(3P) manpage explains why this happens), we can get a new
> destructor running on old unrelated data.
>
> The not-as-great side of not re-using keys is that our current
> implementation
> is limited to 128 keys so we can run out of them. But this patch doesn't
> make
> this any worse than before.
>
> Signed-off-by: Nadav Har'El <n...@scylladb.com>
> ---
> libc/pthread.cc | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/libc/pthread.cc b/libc/pthread.cc
> index 62db224..781ff3a 100644
> --- a/libc/pthread.cc
> +++ b/libc/pthread.cc
> @@ -275,8 +275,19 @@ extern "C" {
>
> int pthread_key_delete(pthread_key_t key)
> {
> - WARN_STUBBED();
> - return EINVAL;
> + std::lock_guard<mutex> guard(tsd_key_mutex);
> + if (key < 0 || key >= (int)tsd_used_keys.size() ||
> !tsd_used_keys[key]) {
> + return EINVAL;
> + }
> + tsd_dtor[key] = nullptr;
> + // TODO: Currently, we keep tsd_used_keys[key] at true so the key will
> + // not be reused. Since pthread_key_delete cannot get rid of existing
> + // data, reusing the key may causes us to later call a new destructor
> + // for old unrelated data. The cost of not reusing keys is that we can
> + // run out of them if many keys are created and deleted (e.g., a
> shared
> + // object is loaded and unloaded)..
> + //tsd_used_keys[key] = false;
> + return 0;
> }
>
> void* pthread_getspecific(pthread_key_t key)
> --
> 2.7.4
>
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