Messages in this thread | | | Subject | Re: [PATCH v18 4/9] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page | From | Mike Kravetz <> | Date | Wed, 10 Mar 2021 10:56:08 -0800 |
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On 3/10/21 7:19 AM, Michal Hocko wrote: > On Mon 08-03-21 18:28:02, Muchun Song wrote: > [...] >> @@ -1447,7 +1486,7 @@ void free_huge_page(struct page *page) >> /* >> * Defer freeing if in non-task context to avoid hugetlb_lock deadlock. >> */ >> - if (!in_task()) { >> + if (in_atomic()) { > > As I've said elsewhere in_atomic doesn't work for CONFIG_PREEMPT_COUNT=n. > We need this change for other reasons and so it would be better to pull > it out into a separate patch which also makes HUGETLB depend on > PREEMPT_COUNT.
Yes, the issue of calling put_page for hugetlb pages from any context still needs work. IMO, that is outside the scope of this series. We already have code in this path which blocks/sleeps.
Making HUGETLB depend on PREEMPT_COUNT is too restrictive. IIUC, PREEMPT_COUNT will only be enabled if we enable: PREEMPT "Preemptible Kernel (Low-Latency Desktop)" PREEMPT_RT "Fully Preemptible Kernel (Real-Time)" or, other 'debug' options. These are not enabled in 'more common' kernels. Of course, we do not want to disable HUGETLB in common configurations.
I'll put together a separate patch where we can discuss the merits of making the change from !in_task to in_atomic, and what work remains in this put_page area. -- Mike Kravetz
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