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| author | Hao Jia <jiahao.os@bytedance.com> | 2023-10-12 11:00:03 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-10-24 10:38:42 +0200 |
| commit | 5ebde09d91707a4a9bec1e3d213e3c12ffde348f (patch) | |
| tree | 087ef04fdf040fe223a2014a208dbf76680658bc /kernel/sched/core.c | |
| parent | Merge tag 'v6.6-rc7' into sched/core, to pick up fixes (diff) | |
| download | linux-5ebde09d91707a4a9bec1e3d213e3c12ffde348f.tar.xz linux-5ebde09d91707a4a9bec1e3d213e3c12ffde348f.zip | |
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@bytedance.com
Reported-by: Igor Raits <igor.raits@gmail.com>
Reported-by: Bagas Sanjaya <bagasdotme@gmail.com>
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/a5dd536d-041a-2ce9-f4b7-64d8d85c86dc@gmail.com
Diffstat (limited to 'kernel/sched/core.c')
| -rw-r--r-- | kernel/sched/core.c | 5 |
1 files changed, 1 insertions, 4 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 264c2eb380d7..dc724f59e495 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); |