The following commit has been merged into the sched/core branch of tip: Commit-ID: 5ebde09d91707a4a9bec1e3d213e3c12ffde348f Gitweb: https://git.kernel.org/tip/5ebde09d91707a4a9bec1e3d213e3c12ffde348f Author: Hao Jia <jiahao.os@xxxxxxxxxxxxx> AuthorDate: Thu, 12 Oct 2023 17:00:03 +08:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 24 Oct 2023 10:38:42 +02:00 sched/core: Fix RQCF_ACT_SKIP leak Igor Raits and Bagas Sanjaya report a RQCF_ACT_SKIP leak warning. This warning may be triggered in the following situations: CPU0 CPU1 __schedule() *rq->clock_update_flags <<= 1;* unregister_fair_sched_group() pick_next_task_fair+0x4a/0x410 destroy_cfs_bandwidth() newidle_balance+0x115/0x3e0 for_each_possible_cpu(i) *i=0* rq_unpin_lock(this_rq, rf) __cfsb_csd_unthrottle() raw_spin_rq_unlock(this_rq) rq_lock(*CPU0_rq*, &rf) rq_clock_start_loop_update() rq->clock_update_flags & RQCF_ACT_SKIP <-- raw_spin_rq_lock(this_rq) The purpose of RQCF_ACT_SKIP is to skip the update rq clock, but the update is very early in __schedule(), but we clear RQCF_*_SKIP very late, causing it to span that gap above and triggering this warning. In __schedule() we can clear the RQCF_*_SKIP flag immediately after update_rq_clock() to avoid this RQCF_ACT_SKIP leak warning. And set rq->clock_update_flags to RQCF_UPDATED to avoid rq->clock_update_flags < RQCF_ACT_SKIP warning that may be triggered later. Fixes: ebb83d84e49b ("sched/core: Avoid multiple calling update_rq_clock() in __cfsb_csd_unthrottle()") Closes: https://lore.kernel.org/all/20230913082424.73252-1-jiahao.os@xxxxxxxxxxxxx Reported-by: Igor Raits <igor.raits@xxxxxxxxx> Reported-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> Suggested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Hao Jia <jiahao.os@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/a5dd536d-041a-2ce9-f4b7-64d8d85c86dc@xxxxxxxxx --- kernel/sched/core.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 264c2eb..dc724f5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5361,8 +5361,6 @@ context_switch(struct rq *rq, struct task_struct *prev, /* switch_mm_cid() requires the memory barriers above. */ switch_mm_cid(rq, prev, next); - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - prepare_lock_switch(rq, next, rf); /* Here we just switch the register state and the stack. */ @@ -6600,6 +6598,7 @@ static void __sched notrace __schedule(unsigned int sched_mode) /* Promote REQ to ACT */ rq->clock_update_flags <<= 1; update_rq_clock(rq); + rq->clock_update_flags = RQCF_UPDATED; switch_count = &prev->nivcsw; @@ -6679,8 +6678,6 @@ static void __sched notrace __schedule(unsigned int sched_mode) /* Also unlocks the rq: */ rq = context_switch(rq, prev, next, &rf); } else { - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - rq_unpin_lock(rq, &rf); __balance_callbacks(rq); raw_spin_rq_unlock_irq(rq);
