Re: [PATCH 2/2] sched_ext: Dump the stall CPU first in watchdog exit

[Tejun Heo]

On Wed, Apr 08, 2026 at 12:11:13PM +0900, Changwoo Min wrote:
> When a watchdog timeout fires, the CPU where the stalled task was
> running is the most relevant piece of information for diagnosing the
> hang. However, if there are many CPUs, the dump can get truncated and
> the stall CPU's information may not appear in the output.
> 
> Add a stall_cpu field to scx_exit_info, thread it through scx_vexit()
> and __scx_exit(), and populate it from cpu_of(rq) in
> check_rq_for_timeouts(). In scx_dump_state(), dump the stall CPU
> before iterating the rest so it always appears at the top of the output.
> 
> Introduce a scx_exit() macro that wraps __scx_exit() with stall_cpu=0
> for all non-stall exit paths, keeping call sites unchanged.

Would it make sense to generalize this so that the exit record the CPU the
exit is triggered on and always dump that CPU first? That should include
stall case, is likely useful for different cases too and we don't have to
add @stall_cpu to the exit functions.

Thanks.

-- 
tejun