On 27 Feb 2026, at 22:54, Ilya Maximets wrote:
> On 2/26/26 11:40 AM, Eelco Chaudron via dev wrote:
>> Coverity reports a data race where pmd_alloc_static_tx_qid() accesses
>> pmd->static_tx_qid in the VLOG_DBG() call without holding the
>> tx_qid_pool_mutex, while id_pool_alloc_id() writes to static_tx_qid
>> with the mutex held.
>>
>> The race occurs because the VLOG_DBG() call is placed after the mutex
>> unlock. While this is a debug-only log with minimal practical impact,
>> it violates proper locking discipline and could theoretically read a
>> stale or inconsistent value.
>>
>> Fix by moving the VLOG_DBG() call before the mutex unlock, ensuring
>> the read of static_tx_qid is protected by the same lock that protects
>> the write.
>>
>> Fixes: 140dd699463a ("dpif-netdev: Incremental addition/deletion of PMD
>> threads.")
>> Signed-off-by: Eelco Chaudron <[email protected]>
>> ---
>> lib/dpif-netdev.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>> index 9df05c4c2..54f3c8c56 100644
>> --- a/lib/dpif-netdev.c
>> +++ b/lib/dpif-netdev.c
>> @@ -6466,10 +6466,10 @@ pmd_alloc_static_tx_qid(struct dp_netdev_pmd_thread
>> *pmd)
>> VLOG_ABORT("static_tx_qid allocation failed for PMD on core %2d"
>> ", numa_id %d.", pmd->core_id, pmd->numa_id);
>> }
>> - ovs_mutex_unlock(&pmd->dp->tx_qid_pool_mutex);
>>
>> VLOG_DBG("static_tx_qid = %d allocated for PMD thread on core %2d"
>> ", numa_id %d.", pmd->static_tx_qid, pmd->core_id,
>> pmd->numa_id);
>> + ovs_mutex_unlock(&pmd->dp->tx_qid_pool_mutex);
>> }
>>
>> static void
>
> This doesn't look right. The mutex is protecting the pool,
> not the variable. THe variable is also only ever accessed
> from the PMD thread itself, so doesn't need locking.
Thanks for the review Ilya,
You are right, I thought I removed all patches for thread local variables,
but it looks I missed one. Will remove it from v2.
//Eelco
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