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An entry naming the > node its page is already on is never queued, so the loop runs without a > voluntary preemption point on a non-preemptible kernel; the existing > cond_resched() calls in the migration code are only reached after a > folio has been queued. nr_pages comes straight from the syscall. > > A 6.6.60 x86_64 kernel with CONFIG_PREEMPT_NONE=3Dy and CONFIG_NUMA=3Dy > reproduces this under QEMU TCG: 50 million entries pointing at a page > already on the target node keep the CPU in do_pages_move() for 42.9 s and > trip the softlockup watchdog; with this patch the same call completes in > 44.3 s without a softlockup. > > Add cond_resched() so that long calls yield periodically. > do_pages_stat() had the same problem; it was fixed by 8e934ab44389. In > current mainline only alpha, hexagon and classic m68k can select > PREEMPT_NONE and they cannot enable CONFIG_NUMA, so this mainly targets > pre-v7.0 stable kernels. > > Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move") > Cc: stable@vger.kernel.org > Signed-off-by: Shao Mingyin > --- > Changes in v2: > - describe the reproduction and the code path, as requested by David > Hildenbrand; no code change > - correct the do_pages_stat() reference (fixed by 8e934ab44389) > Link: https://lore.kernel.org/all/20261107213856462Jx8pIdgdtLvPLfOFTwV4X@= zte.com.cn/ > > mm/migrate.c | 2 ++ > 1 file changed, 2 insertions(+) > Acked-by: Zi Yan --=20 Best Regards, Yan, Zi