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author | Peter Zijlstra <peterz@infradead.org> | 2020-05-11 14:13:00 +0200 |
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committer | Peter Zijlstra <peterz@infradead.org> | 2020-11-10 18:38:57 +0100 |
commit | 565790d28b1e33ee2f77bad5348b99f6dfc366fd (patch) | |
tree | 179b55e6e483c0daf2975f95ccf57401fad0e7d6 /kernel/sched/sched.h | |
parent | a8b62fd0850503cf1e557d7e5a98d3f1f5c25eef (diff) | |
download | linux-565790d28b1e33ee2f77bad5348b99f6dfc366fd.tar.bz2 |
sched: Fix balance_callback()
The intent of balance_callback() has always been to delay executing
balancing operations until the end of the current rq->lock section.
This is because balance operations must often drop rq->lock, and that
isn't safe in general.
However, as noted by Scott, there were a few holes in that scheme;
balance_callback() was called after rq->lock was dropped, which means
another CPU can interleave and touch the callback list.
Rework code to call the balance callbacks before dropping rq->lock
where possible, and otherwise splice the balance list onto a local
stack.
This guarantees that the balance list must be empty when we take
rq->lock. IOW, we'll only ever run our own balance callbacks.
Reported-by: Scott Wood <swood@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201023102346.203901269@infradead.org
Diffstat (limited to 'kernel/sched/sched.h')
-rw-r--r-- | kernel/sched/sched.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index df80bfcea92e..738a00b9237a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1221,6 +1221,9 @@ static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf) rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); rf->clock_update_flags = 0; #endif +#ifdef CONFIG_SMP + SCHED_WARN_ON(rq->balance_callback); +#endif } static inline void rq_unpin_lock(struct rq *rq, struct rq_flags *rf) |