Hi Cédric,
>-----Original Message-----
>From: Cédric Le Goater <c...@redhat.com>
>Sent: Friday, December 22, 2023 12:01 AM
>Subject: Re: [PULL 20/47] backends/iommufd: Introduce the iommufd object
>
>[ ... ]
>
>
>> +static void iommufd_backend_init(Object *obj)
>> +{
>> + IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
>> +
>> + be->fd = -1;
>> + be->users = 0;
>> + be->owned = true;
>> + qemu_mutex_init(&be->lock);> +}
>> +
>> +static void iommufd_backend_finalize(Object *obj)
>> +{
>> + IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
>> +
>> + if (be->owned) {
>> + close(be->fd);
>> + be->fd = -1;
>> + }
>> +}
>> +
>> +static void iommufd_backend_set_fd(Object *obj, const char *str, Error
>**errp)
>> +{
>> + IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
>> + int fd = -1;
>> +
>> + fd = monitor_fd_param(monitor_cur(), str, errp);
>> + if (fd == -1) {
>> + error_prepend(errp, "Could not parse remote object fd %s:", str);
>> + return;
>> + }
>> + qemu_mutex_lock(&be->lock);
>> + be->fd = fd;
>> + be->owned = false;
>> + qemu_mutex_unlock(&be->lock);
>> + trace_iommu_backend_set_fd(be->fd);
>> +}
>> +
>> +static bool iommufd_backend_can_be_deleted(UserCreatable *uc)
>> +{
>> + IOMMUFDBackend *be = IOMMUFD_BACKEND(uc);
>> +
>> + return !be->users;
>
>Coverity CID 1531549 reports a concurrent data access violation because
>be->users is being accessed without holding the mutex.
>
>I wonder how useful is this mutex anyhow, since the code paths should
>be protected by the BQL lock. If you agree, I will send an update to
>simply drop be->lock and solve this report.
Make sense on my side, thanks for help fixing.
BRs.
Zhenzhong
