The patch titled
Subject: mm/swap.c: workaround for_each_cpu() bug on UP kernel
has been added to the -mm tree. Its filename is
mm-swapc-workaround-for_each_cpu-bug-on-up-kernel.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-swapc-workaround-for_each_cpu-bug-on-up-kernel.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-swapc-workaround-for_each_cpu-bug-on-up-kernel.patch
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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: mm/swap.c: workaround for_each_cpu() bug on UP kernel
Since for_each_cpu(cpu, mask) added by commit 2d3854a37e8b767a ("cpumask:
introduce new API, without changing anything") did not evaluate the mask
argument if NR_CPUS == 1 due to CONFIG_SMP=n, lru_add_drain_all() is
hitting WARN_ON() at __flush_work() added by commit 4d43d395fed12463
("workqueue: Try to catch flush_work() without INIT_WORK().")
by unconditionally calling flush_work() [1].
We should fix for_each_cpu() etc. but we need enough grace period for
allowing people to test and fix unexpected behaviors including build
failures. Therefore, this patch temporarily duplicates flush_work() for
NR_CPUS == 1 case. This patch will be reverted after for_each_cpu() etc.
are fixed.
[1] https://lkml.kernel.org/r/18a30387-6aa5-6123-e67c-57579ecc3f38@xxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1549533189-9177-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Acked-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Reviewed by: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Chris Metcalf <chris.d.metcalf@xxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/swap.c~mm-swapc-workaround-for_each_cpu-bug-on-up-kernel
+++ a/mm/swap.c
@@ -694,11 +694,16 @@ void lru_add_drain_all(void)
INIT_WORK(work, lru_add_drain_per_cpu);
queue_work_on(cpu, mm_percpu_wq, work);
cpumask_set_cpu(cpu, &has_work);
+#if NR_CPUS == 1
+ flush_work(work);
+#endif
}
}
+#if NR_CPUS != 1
for_each_cpu(cpu, &has_work)
flush_work(&per_cpu(lru_add_drain_work, cpu));
+#endif
mutex_unlock(&lock);
}
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
mm-swapc-workaround-for_each_cpu-bug-on-up-kernel.patch
memcg-killed-threads-should-not-invoke-memcg-oom-killer.patch
mmoom-dont-kill-global-init-via-memoryoomgroup.patch
info-task-hung-in-generic_file_write_iter.patch
info-task-hung-in-generic_file_write-fix.patch
