6.18-stable review patch. If anyone has any objections, please let me know.
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From: Fernand Sieber sieberf@amazon.com
commit 127b90315ca07ccad2618db7ba950a63e3b32d22 upstream.
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 oliver.sang@intel.com Closes: https://lore.kernel.org/oe-lkp/202510211205.1e0f5223-lkp@intel.com Suggested-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Fernand Sieber sieberf@amazon.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://patch.msgid.link/20251106104022.195157-1-sieberf@amazon.com Cc: Holger Hoffstätte holger@applied-asynchrony.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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(-)
--- 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); --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -1493,7 +1493,7 @@ static bool dequeue_task_scx(struct rq * 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, --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8993,7 +8993,7 @@ static void put_prev_task_fair(struct rq */ 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;
--- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1490,7 +1490,7 @@ static void requeue_task_rt(struct rq *r
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); --- a/kernel/sched/syscalls.c +++ b/kernel/sched/syscalls.c @@ -1351,7 +1351,7 @@ 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);
preempt_disable(); rq_unlock_irq(rq, &rf); @@ -1420,12 +1420,13 @@ EXPORT_SYMBOL(yield); */ int __sched yield_to(struct task_struct *p, bool preempt) { - 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);