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b485c6f1f9
A soft lockup bug in kcompactd was reported in a private bugzilla with
the following visible in dmesg;
watchdog: BUG: soft lockup - CPU#33 stuck for 26s! [kcompactd0:479]
watchdog: BUG: soft lockup - CPU#33 stuck for 52s! [kcompactd0:479]
watchdog: BUG: soft lockup - CPU#33 stuck for 78s! [kcompactd0:479]
watchdog: BUG: soft lockup - CPU#33 stuck for 104s! [kcompactd0:479]
The machine had 256G of RAM with no swap and an earlier failed
allocation indicated that node 0 where kcompactd was run was potentially
unreclaimable;
Node 0 active_anon:29355112kB inactive_anon:2913528kB active_file:0kB
inactive_file:0kB unevictable:64kB isolated(anon):0kB isolated(file):0kB
mapped:8kB dirty:0kB writeback:0kB shmem:26780kB shmem_thp:
0kB shmem_pmdmapped: 0kB anon_thp: 23480320kB writeback_tmp:0kB
kernel_stack:2272kB pagetables:24500kB all_unreclaimable? yes
Vlastimil Babka investigated a crash dump and found that a task
migrating pages was trying to drain PCP lists;
PID: 52922 TASK: ffff969f820e5000 CPU: 19 COMMAND: "kworker/u128:3"
Call Trace:
__schedule
schedule
schedule_timeout
wait_for_completion
__flush_work
__drain_all_pages
__alloc_pages_slowpath.constprop.114
__alloc_pages
alloc_migration_target
migrate_pages
migrate_to_node
do_migrate_pages
cpuset_migrate_mm_workfn
process_one_work
worker_thread
kthread
ret_from_fork
This failure is specific to CONFIG_PREEMPT=n builds. The root of the
problem is that kcompact0 is not rescheduling on a CPU while a task that
has isolated a large number of the pages from the LRU is waiting on
kcompact0 to reschedule so the pages can be released. While
shrink_inactive_list() only loops once around too_many_isolated, reclaim
can continue without rescheduling if sc->skipped_deactivate == 1 which
could happen if there was no file LRU and the inactive anon list was not
low.
Link: https://lkml.kernel.org/r/20220203100326.GD3301@suse.de
Fixes: d818fca1ca ("mm/vmscan: throttle reclaim and compaction when too may pages are isolated")
Signed-off-by: Mel Gorman <mgorman@suse.de>
Debugged-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
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In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.