Re: [PATCH 1/2] sched_ext: Prevent SCX_KICK_WAIT deadlock by serialization

[Christian Loehle <christian.loehle@arm.com>]

On 3/16/26 17:46, Tejun Heo wrote:
> Hello,
> 
> On Mon, Mar 16, 2026 at 10:02:48AM +0000, Christian Loehle wrote:
>> @@ -5686,11 +5718,20 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
>>  		 * task is picked subsequently. The latter is necessary to break
>>  		 * the wait when $cpu is taken by a higher sched class.
>>  		 */
>> -		if (cpu != cpu_of(this_rq))
>> +		if (cpu != this_cpu)
>>  			smp_cond_load_acquire(wait_kick_sync, VAL != ksyncs[cpu]);
> 
> Given that irq_work is executed at the end of IRQ handling, we can just
> reschedule the irq work when the condition is not met (or separate that out
> into its own irq_work). That way, I think we can avoid the global lock.
> 
I'll go poke at it some more, but I think it's not guaranteed that B actually
advances kick_sync if A keeps kicking. At least not if the handling is in HARD irqwork?
Or what would the separated out irq work do differently?