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Merge pull request #361 from sched-ext/rustland-fix-stall

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scx_rustland_core: fix potential race in dispatch_task()
This commit is contained in:
Andrea Righi 2024-06-16 17:40:17 +02:00 committed by GitHub
commit 38141905eb
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1 changed files with 17 additions and 7 deletions
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24
rust/scx_rustland_core/assets/bpf/main.bpf.c
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@ -373,6 +373,20 @@ dispatch_task(struct task_struct *p, u64 dsq_id,
p->pid, p->comm, dsq_id, enq_flags, slice);
break;
default:
tctx = lookup_task_ctx(p);
if (!tctx) {
/*
* If the task doesn't have a context anymore, simply
* bounce it to the first CPU available.
*/
scx_bpf_dispatch(p, SHARED_DSQ, slice, enq_flags);
__sync_fetch_and_add(&nr_bounce_dispatches, 1);
dbg_msg("dispatch: pid=%d (%s) dsq=%llu enq_flags=%llx slice=%llu bounce",
p->pid, p->comm, dsq_id, enq_flags, slice);
return;
}
/*
* Dispatch a task to a specific per-CPU DSQ if the target CPU
* can be used (according to the cpumask), otherwise redirect
@ -391,10 +405,6 @@ dispatch_task(struct task_struct *p, u64 dsq_id,
*/
scx_bpf_dispatch(p, dsq_id, slice, enq_flags);
tctx = lookup_task_ctx(p);
if (!tctx)
return;
/* Read current cpumask generation counter */
curr_cpumask_cnt = tctx->cpumask_cnt;
@ -716,7 +726,7 @@ void BPF_STRUCT_OPS(rustland_dispatch, s32 cpu, struct task_struct *prev)
break;
}
/* Consume all tasks enqueued in the current CPU's DSQ first */
/* Consume all tasks enqueued in the current CPU's DSQ */
bpf_repeat(MAX_ENQUEUED_TASKS) {
if (!scx_bpf_consume(cpu_to_dsq(cpu)))
break;
@ -782,8 +792,8 @@ void BPF_STRUCT_OPS(rustland_update_idle, s32 cpu, bool idle)
if (usersched_has_pending_tasks()) {
set_usersched_needed();
/*
* Wake up the idle CPU, so that it can immediately accept
* dispatched tasks.
* Wake up the idle CPU and trigger a resched, so that it can
* immediately accept dispatched tasks.
*/
if (!low_power || !nr_running)
scx_bpf_kick_cpu(cpu, 0);