Messages in this thread | | | Date | Thu, 16 Feb 2023 19:02:59 +0800 | Subject | Re: [PATCH] iommu: Avoid softlockup and rcu stall in fq_flush_timeout(). | From | Peng Zhang <> |
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在 2023/2/16 16:49, Hillf Danton 写道: > On Thu, 16 Feb 2023 15:11:48 +0800 Peng Zhang <zhangpeng.00@bytedance.com> >> There is softlockup under fio pressure test with smmu enabled: >> watchdog: BUG: soft lockup - CPU#81 stuck for 22s! [swapper/81:0] > > What is your kernel version? Rcu stall occurs in kernel version 5.4. The test where the softlockup happened was not done by me, so I don't know the kernel version. However, it is the same as the code logic of fq_flush_timeout in the mainline kernel.
>> This is because the timer callback fq_flush_timeout may run more than >> 10ms, and timer may be processed continuously in the softirq so trigger >> softlockup and rcu stall. We can use work to deal with fq_ring_free for >> each cpu which may take long time, that to avoid triggering softlockup >> and rcu stall. >> >> This patch is modified from the patch[1] of openEuler. > > Because of a timer hog observed on your system with 128 CPUs for instance > does it make any sense to ask Peter to apply the patch for his 2-CPU box? What is 2-CPU box?
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