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    SubjectRe: [PATCH 1/1] mm/page_alloc: add scheduling point to free_unref_page_list
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    On 3/3/22 00:34, Andrew Morton wrote:
    > On Tue, 1 Mar 2022 20:38:25 -0500 wangjianxing <wangjianxing@loongson.cn> wrote:
    >
    >> free a large list of pages maybe cause rcu_sched starved on
    >> non-preemptible kernels
    >>
    >> rcu: rcu_sched kthread starved for 5359 jiffies! g454793 f0x0
    >> RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=19
    >> [...]
    >> Call Trace:
    >> free_unref_page_list+0x19c/0x270
    >> release_pages+0x3cc/0x498
    >> tlb_flush_mmu_free+0x44/0x70
    >> zap_pte_range+0x450/0x738
    >> unmap_page_range+0x108/0x240
    >> unmap_vmas+0x74/0xf0
    >> unmap_region+0xb0/0x120
    >> do_munmap+0x264/0x438
    >> vm_munmap+0x58/0xa0
    >> sys_munmap+0x10/0x20
    >> syscall_common+0x24/0x38
    >
    > Thanks.
    >
    > How did this large list of pages come about?

    Looks like it came from TLB batching. But I got lost in the maze of it
    trying to figure out how large the batch can grow.

    > Will people be seeing this message in upstream kernels, or is it
    > specific to some caller code which you have added?
    >
    > Please always include details such as this so that others can determine
    > whether the fix should be backported into -stable kernels.
    >
    >

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