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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [stable-6.6.y] mm: khugepaged refuses to freeze Message-ID: References: <3d0f189b-faab-4452-b9cc-8f4e7a15025f@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3d0f189b-faab-4452-b9cc-8f4e7a15025f@linux.alibaba.com> X-Stat-Signature: oro11izd1h8k4eqt99owh5j4jsozo51m X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 84A05160004 X-HE-Tag: 1770349140-424718 X-HE-Meta: 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 41IdGVK6 vKGvE/pLh4MWnne1U6vPgW8pb5n+acMKwJDF7pYovf+TCXhQ1subhIo2XPhe1Jc5JJh9Kg8Hc51KFCHp3cd7KtoeqKVjb3d2wrgZ5JTcrtZtB6t2gLmmJpGSOxhVaQNI0zuF51kXdph946Pn//OY3rR06+l0bsovA4lNAoeeMkDF/pmbQlGp2RlcG6kYCCIjotjtaspyVgELyyuij6l/T4/0demckQHkn7Zk5Q7g3tvq/uFg0lvBWEyocHhJT0FxZgCF3R+ONoadiCvP+qt6m2tbQ9HZz4/TNsnUb5bSBdMekpbh4Urexw3GkpVTeOROKhMY87pADrWfqFVd+fPTe7SQj54wikPdlouRqvdlMB5igoMcUlt8WLWjJ6UzplAeLUeHGKx+H4eBRWaw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (26/02/06 11:33), Baolin Wang wrote: > > Freezing remaining freezable tasks failed after 20.004 seconds (1 tasks refusing to freeze, wq_busy=0): > > task:khugepaged state:D stack:0 pid:1345 ppid:2 flags:0x00004000 > > Call Trace: > > > > schedule+0x523/0x16a0 > > ? sysvec_apic_timer_interrupt+0xf/0x90 > > ? asm_sysvec_apic_timer_interrupt+0x16/0x20 > > ? wait_for_completion_io_timeout+0xc5/0x170 > > schedule_timeout+0x23b/0x6e0 > > ? __pfx_process_timeout+0x10/0x10 > > ? wait_for_completion_io_timeout+0xc5/0x170 > > io_schedule_timeout+0x3f/0x80 > > wait_for_completion_io_timeout+0xe4/0x170 > > submit_bio_wait+0x79/0xc0 > > swap_readpage+0x150/0x2d0 > > ? __pfx_submit_bio_wait_endio+0x10/0x10 > > swap_cluster_readahead+0x3be/0x750 > > ? __pfx_workingset_update_node+0x10/0x10 > > shmem_swapin+0xa7/0x100 > > shmem_swapin_folio+0xcd/0x2e0 > > shmem_get_folio+0x237/0x580 > > collapse_file+0x247/0x1280 > > hpage_collapse_scan_file+0x26e/0x380 > > khugepaged+0x43b/0x810 > > kthread+0xfb/0x120 > > ? __pfx_khugepaged+0x10/0x10 > > ? __pfx_kthread+0x10/0x10 > > ret_from_fork+0x38/0x50 > > ? __pfx_kthread+0x10/0x10 > > ret_from_fork_asm+0x1b/0x30 > > > > ... > > > > The system is using zram swap. I wonder if khugepaged should > > be suspend/freeze aware. Does something like below make sense? > > Or is the problem elsewhere? > > > > --- > > mm/khugepaged.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index eff9e3061925..fa6a018b20a8 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -1894,6 +1894,9 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > > xas_set(&xas, index); > > folio = xas_load(&xas); > > + if (try_to_freeze()) > > + goto xa_unlocked; > > + > > VM_BUG_ON(index != xas.xa_index); > > if (is_shmem) { > > if (!folio) { > > Your analysis is reasonable. When the system is freezing, khugepaged is > still trying to swap-in shmem to collapse, which prevents the system from > entering suspend state. However, it’s not only shmem that will swap in, > collapsing anonymous folios may also trigger swap-in operations. Right, I thought about it but wasn't sure. Could the inner loop (e.g. collapse_file() in this particular case) loop long enough to fail suspend w/o ever giving the outer loop (khugepaged_do_scan()) a chance to freeze?