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| author | Vincent Donnefort <vincent.donnefort@arm.com> | 2021-11-04 17:51:20 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-11-26 11:58:43 +0100 |
| commit | 26efb10b1e2224af9b40f2a6917fbb53e4bd1387 (patch) | |
| tree | 086eddcd0173297c4fdbcab27cdc1fc3de093ebf | |
| parent | 9b4fb12db85c0031f858b5f57bacf8ad49470de6 (diff) | |
| download | linux-stable-26efb10b1e2224af9b40f2a6917fbb53e4bd1387.tar.gz linux-stable-26efb10b1e2224af9b40f2a6917fbb53e4bd1387.tar.bz2 linux-stable-26efb10b1e2224af9b40f2a6917fbb53e4bd1387.zip | |
sched/core: Mitigate race cpus_share_cache()/update_top_cache_domain()
[ Upstream commit 42dc938a590c96eeb429e1830123fef2366d9c80 ]
Nothing protects the access to the per_cpu variable sd_llc_id. When testing
the same CPU (i.e. this_cpu == that_cpu), a race condition exists with
update_top_cache_domain(). One scenario being:
CPU1 CPU2
==================================================================
per_cpu(sd_llc_id, CPUX) => 0
partition_sched_domains_locked()
detach_destroy_domains()
cpus_share_cache(CPUX, CPUX) update_top_cache_domain(CPUX)
per_cpu(sd_llc_id, CPUX) => 0
per_cpu(sd_llc_id, CPUX) = CPUX
per_cpu(sd_llc_id, CPUX) => CPUX
return false
ttwu_queue_cond() wouldn't catch smp_processor_id() == cpu and the result
is a warning triggered from ttwu_queue_wakelist().
Avoid a such race in cpus_share_cache() by always returning true when
this_cpu == that_cpu.
Fixes: 518cd6234178 ("sched: Only queue remote wakeups when crossing cache boundaries")
Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211104175120.857087-1-vincent.donnefort@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/sched/core.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4a0a754f24c8..69c6c740da11 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1885,6 +1885,9 @@ out: bool cpus_share_cache(int this_cpu, int that_cpu) { + if (this_cpu == that_cpu) + return true; + return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); } #endif /* CONFIG_SMP */ |