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SubjectRe: [patch 11/17] Implement immediate update via stop_machine_run
Hi

> -Updating immediate values, cannot rely on smp_call_function() b/c synchronizing
> cpus using IPIs leads to deadlocks. Process A held a read lock on
> tasklist_lock, then process B called apply_imv_update(). Process A received the
> IPI and begins executing ipi_busy_loop(). Then process C takes a write lock
> irq on the task list lock, before receiving the IPI. Thus, process A holds up
> process C, and C can't get an IPI b/c interrupts are disabled. Solve this
> problem by using a new 'ALL_CPUS' parameter to stop_machine_run(). Which
> runs a function on all cpus after they are busy looping and have disabled
> irqs. Since this is done in a new process context, we don't have to worry
> about interrupted spin_locks. Also, less lines of code. Has survived 24 hours+
> of testing...

it seems this patch is must, Why do you separate patch [10/17] and [11/17]?
this patch remove almost portion of [10/17].
IMHO these patch merge into 1 patch is better.


> +static int stop_machine_imv_update(void *imv_ptr)
> +{
> + struct __imv *imv = imv_ptr;
> +
> + if (!wrote_text) {

it seems racy.
Why don't need test_and_set?

I think your stop_machine_run(ALL_CPUS) call fn concurrency...


> + text_poke((void *)imv->imv, (void *)imv->var, imv->size);
> + wrote_text = 1;
> + smp_wmb(); /* make sure other cpus see that this has run */
> + } else
> + sync_core();
> +
> + flush_icache_range(imv->imv, imv->imv + imv->size);
> +
> + return 0;
> +}
> +




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