On 12/12/19 3:52 PM, Waiman Long wrote: > On 12/12/19 2:22 PM, Mike Kravetz wrote: >> On 12/12/19 11:04 AM, Davidlohr Bueso wrote: >>> There have been deadlock reports[1, 2] where put_page is called >>> from softirq context and this causes trouble with the hugetlb_lock, >>> as well as potentially the subpool lock. >>> >>> For such an unlikely scenario, lets not add irq dancing overhead >>> to the lock+unlock operations, which could incur in expensive >>> instruction dependencies, particularly when considering hard-irq >>> safety. For example PUSHF+POPF on x86. >>> >>> Instead, just use a workqueue and do the free_huge_page() in regular >>> task context. >>> >>> [1] https://lore.kernel.org/lkml/20191211194615.18502-1-longman@xxxxxxxxxx/ >>> [2] https://lore.kernel.org/lkml/20180905112341.21355-1-aneesh.kumar@xxxxxxxxxxxxx/ >>> >>> Reported-by: Waiman Long <longman@xxxxxxxxxx> >>> Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> >>> Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx> >> Thank you Davidlohr. >> >> The patch does seem fairly simple and straight forward. I need to brush up >> on my workqueue knowledge to provide a full review. >> >> Longman, >> Do you have a test to reproduce the issue? If so, can you try running with >> this patch. > Yes, I do have a test that can reproduce the issue. I will run it with > the patch and report the status tomorrow. I don't think Davidlohr's patch is ready for prime time yet. So I will wait until a better version is available. Cheers, Longman
