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Sashiko AI review found 1 potential > > issue(s) to consider: > > > > - ## [High] Infinite timeslice and preemption bypass during SCX proxy > > execution due to a mismatch between slice decrement (execution context) > > and slice checking (scheduling context). > > > > commit ff57ff4a11692a1b0d98a6cd57257eb58a1bd864 > > Author: Hui Su > > > > Does this cause an infinite timeslice for SCX tasks during proxy execution? > > > > When an SCX task acts as a donor in proxy execution, task_tick_scx() sets > > curr to rq->donor. However, update_curr_scx() applies the slice decrement > > to the execution context (rq->curr): > > > > static void update_curr_scx(struct rq *rq) > > { > > struct task_struct *curr = rq->curr; > > ... > > if (curr->scx.slice != SCX_SLICE_INF) > > curr->scx.slice -= min_t(u64, curr->scx.slice, delta_exec); > > ... > > } > > > > Later in task_tick_scx(), the slice check is performed against the donor > > task which was never decremented: > > > > if (!curr->scx.slice) > > resched_curr(rq); > > > > Since the donor's slice doesn't decrease, it will never hit zero, meaning > > resched_curr(rq) is bypassed indefinitely. > > > > Additionally, if the proxy task is SCX but the donor is not, > > task_tick_scx() returns early here because the donor is not an SCX task, > > skipping the SCX tick processing completely. Should the slice management > > be explicitly tied to the execution context rather than the donor? > > > > -- > > Sashiko AI review > > Thanks for the report. > > This configuration is currently unreachable. CONFIG_SCHED_PROXY_EXEC > depends on !SCHED_CLASS_EXT, so sched_ext and proxy execution cannot be > enabled together. > > When CONFIG_SCHED_CLASS_EXT=y, proxy execution is disabled and rq->donor > and rq->curr alias the same task. Therefore task_tick_scx() using > rq->donor and update_curr_scx() using rq->curr still operate on the same > task, and the slice decrement and check cannot diverge. > > The sched_ext change in this patch only adapts it to the new task_tick() > interface for the currently supported configuration. > > If sched_ext and proxy execution are made compatible in the future, the > SCX donor/execution-context ownership will need to be handled as part of > that integration. They should be compatible soon: https://lore.kernel.org/r/20260831134338.1531664-1-arighi@nvidia.com/ It'd be good to handle SCX donor/execution context ownership in this serie as well, or we can coordinate to figure out the required changes. I haven't looked at the whole patch series yet (will do soon), this is JFYI. :) Thanks, -Andrea