On Thu, 3 Apr 2025 at 22:23, Bernd Schubert <bschubert@xxxxxxx> wrote:
> +/**
> + * Get the next unique ID for a request
> + */
> +static inline u64 fuse_get_unique(struct fuse_iqueue *fiq)
> +{
> + int step = FUSE_REQ_ID_STEP * (task_cpu(current));
> + u64 cntr = this_cpu_inc_return(*fiq->reqctr);
> +
> + return cntr * FUSE_REQ_ID_STEP * NR_CPUS + step;
Thinking a bit... this looks wrong.
The reason is that the task could be migrated to a different CPU
between the task_cpu() and the this_cpu_inc_return(), resulting in a
possibly duplicated value.
This could be fixed with a preempt_disable()/preempt_enable() pair,
but I think it would be cleaner to go with my original idea and
initialize the percpu counters to CPUID and increment by NR_CPU *
FUSE_REQ_ID_STEP when fetching a new value.
Thanks,
Miklos
