From 8d8dd8ae89eaa78b37fc85528e926029f5facbdf Mon Sep 17 00:00:00 2001 From: Tao Cui Date: Sat, 15 Aug 2026 10:20:17 +0800 Subject: sched_ext: Don't BUG_ON a destroyed DSQ in process_deferred_reenq_users scx_bpf_dsq_reenq() queues a deferred reenq (dru) that runs from run_deferred(), not ops.dispatch(). If the DSQ is destroyed before the dru runs, process_deferred_reenq_users() sees dsq->id == SCX_DSQ_INVALID and hits the BUG_ON. destroy_dsq() doesn't flush pending drus, so just skip. tj: Read dsq->id once with READ_ONCE(). Reading it separately in the INVALID check and the BUG_ON would leave a window where destroy_dsq() can invalidate the id between the two reads and still trigger the BUG_ON. Fixes: 84b1a0ea0b7c ("sched_ext: Implement scx_bpf_dsq_reenq() for user DSQs") Cc: stable@vger.kernel.org # v7.1+ Signed-off-by: Tao Cui Signed-off-by: Tejun Heo --- kernel/sched/ext/ext.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 0b31a9976e97..950d98508463 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -4613,7 +4613,7 @@ static void process_deferred_reenq_users(struct rq *rq) while (true) { struct scx_dispatch_q *dsq; - u64 reenq_flags; + u64 dsq_id, reenq_flags; scoped_guard (raw_spinlock, &rq->scx.deferred_reenq_lock) { struct scx_deferred_reenq_user *dru = @@ -4636,7 +4636,12 @@ static void process_deferred_reenq_users(struct rq *rq) /* see schedule_dsq_reenq() */ smp_mb(); - BUG_ON(dsq->id & SCX_DSQ_FLAG_BUILTIN); + /* destroy_dsq() may have raced and invalidated @dsq, nothing to reenq */ + dsq_id = READ_ONCE(dsq->id); + if (unlikely(dsq_id == SCX_DSQ_INVALID)) + continue; + + BUG_ON(dsq_id & SCX_DSQ_FLAG_BUILTIN); reenq_user(rq, dsq, reenq_flags); } } -- cgit v1.2.3