diff options
| author | Michal Hocko <mhocko@suse.com> | 2018-02-01 03:16:19 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-02-01 04:18:36 +0300 |
| commit | 9852a7212324fd25f896932f4f4607ce47b0a22f (patch) | |
| tree | 83203a3d766a4e72a1c087eea9ea7e089aab122e /mm/swap.c | |
| parent | 0486a38bcc4749808edbc848f1bcf232042770fc (diff) | |
| download | linux-9852a7212324fd25f896932f4f4607ce47b0a22f.tar.xz | |
mm: drop hotplug lock from lru_add_drain_all()
Pulling cpu hotplug locks inside the mm core function like
lru_add_drain_all just asks for problems and the recent lockdep splat
[1] just proves this. While the usage in that particular case might be
wrong we should avoid the locking as lru_add_drain_all() is used in many
places. It seems that this is not all that hard to achieve actually.
We have done the same thing for drain_all_pages which is analogous by
commit a459eeb7b852 ("mm, page_alloc: do not depend on cpu hotplug locks
inside the allocator"). All we have to care about is to handle
- the work item might be executed on a different cpu in worker from
unbound pool so it doesn't run on pinned on the cpu
- we have to make sure that we do not race with page_alloc_cpu_dead
calling lru_add_drain_cpu
the first part is already handled because the worker calls lru_add_drain
which disables preemption when calling lru_add_drain_cpu on the local
cpu it is draining. The later is true because page_alloc_cpu_dead is
called on the controlling CPU after the hotplugged CPU vanished
completely.
[1] http://lkml.kernel.org/r/089e0825eec8955c1f055c83d476@google.com
[add a cpu hotplug locking interaction as per tglx]
Link: http://lkml.kernel.org/r/20171116120535.23765-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap.c')
| -rw-r--r-- | mm/swap.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/mm/swap.c b/mm/swap.c index 38e1b6374a97..e824c800adca 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -688,7 +688,14 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy) static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); -void lru_add_drain_all_cpuslocked(void) +/* + * Doesn't need any cpu hotplug locking because we do rely on per-cpu + * kworkers being shut down before our page_alloc_cpu_dead callback is + * executed on the offlined cpu. + * Calling this function with cpu hotplug locks held can actually lead + * to obscure indirect dependencies via WQ context. + */ +void lru_add_drain_all(void) { static DEFINE_MUTEX(lock); static struct cpumask has_work; @@ -724,13 +731,6 @@ void lru_add_drain_all_cpuslocked(void) mutex_unlock(&lock); } -void lru_add_drain_all(void) -{ - get_online_cpus(); - lru_add_drain_all_cpuslocked(); - put_online_cpus(); -} - /** * release_pages - batched put_page() * @pages: array of pages to release |