Messages in this thread | | | Date | Fri, 10 Dec 2021 18:13:09 +0000 | Subject | Re: [PATCH v2 01/11] iommu/iova: Fix race between FQ timeout and teardown | From | Robin Murphy <> |
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On 2021-12-10 18:04, John Garry via iommu wrote: > On 10/12/2021 17:54, Robin Murphy wrote: >> From: Xiongfeng Wang<wangxiongfeng2@huawei.com> >> >> It turns out to be possible for hotplugging out a device to reach the >> stage of tearing down the device's group and default domain before the >> domain's flush queue has drained naturally. At this point, it is then >> possible for the timeout to expire just*before* the del_timer() call > > super nit: "just*before* the" - needs a whitespace before "before" :)
Weird... the original patch file here and the copy received by lore via linux-iommu look fine, gremlins in your MUA or delivery path perhaps?
>> from free_iova_flush_queue(), such that we then proceed to free the FQ >> resources while fq_flush_timeout() is still accessing them on another >> CPU. Crashes due to this have been observed in the wild while removing >> NVMe devices. >> >> Close the race window by using del_timer_sync() to safely wait for any >> active timeout handler to finish before we start to free things. We >> already avoid any locking in free_iova_flush_queue() since the FQ is >> supposed to be inactive anyway, so the potential deadlock scenario does >> not apply. >> >> Fixes: 9a005a800ae8 ("iommu/iova: Add flush timer") >> Signed-off-by: Xiongfeng Wang<wangxiongfeng2@huawei.com> >> [ rm: rewrite commit message ] >> Signed-off-by: Robin Murphy<robin.murphy@arm.com> > > FWIW, > > Reviewed-by: John Garry <john.garry@huawei.com>
Thanks John!
Robin.
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