From d4ed8eac96348fdf65c285a1b756808581a80a69 Mon Sep 17 00:00:00 2001 From: Fernand Sieber Date: Thu, 6 Nov 2025 12:40:10 +0200 Subject: [PATCH] sched/proxy: Yield the donor task When executing a task in proxy context, handle yields as if they were requested by the donor task. This matches the traditional PI semantics of yield() as well. This avoids scenario like proxy task yielding, pick next task selecting the same previous blocked donor, running the proxy task again, etc. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202510211205.1e0f5223-lkp@intel.com Suggested-by: Peter Zijlstra Signed-off-by: Fernand Sieber Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20251106104022.195157-1-sieberf@amazon.com Signed-off-by: Brahmajit Das --- kernel/sched/deadline.c | 2 +- kernel/sched/ext.c | 4 ++-- kernel/sched/fair.c | 2 +- kernel/sched/rt.c | 2 +- kernel/sched/syscalls.c | 5 +++-- 5 files changed, 8 insertions(+), 7 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 19b1a8b81c76..d3be71d5a9cc 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2143,7 +2143,7 @@ static void yield_task_dl(struct rq *rq) * it and the bandwidth timer will wake it up and will give it * new scheduling parameters (thanks to dl_yielded=1). */ - rq->curr->dl.dl_yielded = 1; + rq->donor->dl.dl_yielded = 1; update_rq_clock(rq); update_curr_dl(rq); diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index b959a70471c1..907eea83294c 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -1493,7 +1493,7 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags static void yield_task_scx(struct rq *rq) { struct scx_sched *sch = scx_root; - struct task_struct *p = rq->curr; + struct task_struct *p = rq->donor; if (SCX_HAS_OP(sch, yield)) SCX_CALL_OP_2TASKS_RET(sch, SCX_KF_REST, yield, rq, p, NULL); @@ -1504,7 +1504,7 @@ static void yield_task_scx(struct rq *rq) static bool yield_to_task_scx(struct rq *rq, struct task_struct *to) { struct scx_sched *sch = scx_root; - struct task_struct *from = rq->curr; + struct task_struct *from = rq->donor; if (SCX_HAS_OP(sch, yield)) return SCX_CALL_OP_2TASKS_RET(sch, SCX_KF_REST, yield, rq, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d30dfd6f18b7..99a10815ca17 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9006,7 +9006,7 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, struct t */ static void yield_task_fair(struct rq *rq) { - struct task_struct *curr = rq->curr; + struct task_struct *curr = rq->donor; struct cfs_rq *cfs_rq = task_cfs_rq(curr); struct sched_entity *se = &curr->se; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 7936d4333731..fb07dcfc60a2 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1490,7 +1490,7 @@ static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head) static void yield_task_rt(struct rq *rq) { - requeue_task_rt(rq, rq->curr, 0); + requeue_task_rt(rq, rq->donor, 0); } static int find_lowest_rq(struct task_struct *task); diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c index a2b06eba44e7..417eb6a63015 100644 --- a/kernel/sched/syscalls.c +++ b/kernel/sched/syscalls.c @@ -1607,7 +1607,7 @@ static void do_sched_yield(void) rq = this_rq_lock_irq(&rf); schedstat_inc(rq->yld_count); - current->sched_class->yield_task(rq); + rq->donor->sched_class->yield_task(rq); #endif /* !CONFIG_SCHED_ALT */ preempt_disable(); @@ -1680,12 +1680,13 @@ int __sched yield_to(struct task_struct *p, bool preempt) #ifdef CONFIG_SCHED_ALT return 0; #else /* !CONFIG_SCHED_ALT */ - struct task_struct *curr = current; + struct task_struct *curr; struct rq *rq, *p_rq; int yielded = 0; scoped_guard (raw_spinlock_irqsave, &p->pi_lock) { rq = this_rq(); + curr = rq->donor; again: p_rq = task_rq(p); -- 2.52.0