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From: Sergey Fedorov <serge.fdrv@gmail.com>
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Date: Fri, 3 Jun 2016 18:34:34 +0300
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Subject: Re: [Qemu-devel] [PATCH v6 10/15] qht: QEMU's fast,
 resizable and scalable Hash Table
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To: "Emilio G. Cota" <cota@braap.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>, MTTCG Devel <mttcg@listserver.greensocs.com>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On 03/06/16 14:01, Emilio G. Cota wrote:
> On Sun, May 29, 2016 at 22:52:27 +0300, Sergey Fedorov wrote:
>>> +/*
>>> + * Find the last valid entry in @head, and swap it with @orig[pos], which has
>>> + * just been invalidated.
>>> + */
>>> +static inline void qht_bucket_fill_hole(struct qht_bucket *orig, int pos)
>>> +{
>>> +    struct qht_bucket *b = orig;
>>> +    struct qht_bucket *prev = NULL;
>>> +    int i;
>>> +
>>> +    if (qht_entry_is_last(orig, pos)) {
>>> +        orig->hashes[pos] = 0;
>>> +        atomic_set(&orig->pointers[pos], NULL);
>>> +        return;
>>> +    }
>>> +    do {
>>> +        for (i = 0; i < QHT_BUCKET_ENTRIES; i++) {
>>> +            if (b->pointers[i]) {
>>> +                continue;
>>> +            }
>>> +            if (i > 0) {
>>> +                return qht_entry_move(orig, pos, b, i - 1);
>>> +            }
>>> +            qht_debug_assert(prev);
>> 'prev' can be NULL if this is the first iteration.
> How can prev be NULL here and that not be a bug? NULL here would
> mean there was a hole before orig[pos]. Or orig[pos] was
> NULL, which is also a bug.

Yeah, you're right.

Kind regards,
Sergey