| Message ID | 20210816074605.30336-1-qiang.zhang@windriver.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm, slub: add cpus_read_lock/unlock() for slab_mem_going_offline_callback() | expand |
On 16.08.21 09:46, qiang.zhang@windriver.com wrote: > From: "Qiang.Zhang" <qiang.zhang@windriver.com> > > The flush_all_cpus_locked() should be called with cpus_read_lock/unlock(), > ensure flush_cpu_slab() can be executed on schedule_on CPU. > > Fixes: 1c84f3c91640 ("mm, slub: fix memory and cpu hotplug related lock ordering issues") Which branch contains this commit? At least not linux.git or linux-next > Signed-off-by: Qiang.Zhang <qiang.zhang@windriver.com> > --- > mm/slub.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/slub.c b/mm/slub.c > index 5543d57cb128..cf3f93abbd3e 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -4593,12 +4593,14 @@ static int slab_mem_going_offline_callback(void *arg) > { > struct kmem_cache *s; > > + cpus_read_lock(); > mutex_lock(&slab_mutex); > list_for_each_entry(s, &slab_caches, list) { > flush_all_cpus_locked(s); > __kmem_cache_do_shrink(s); > } > mutex_unlock(&slab_mutex); > + cpus_read_unlock(); > > return 0; > } > Memory notifiers are getting called from online_pages()/offline_pages(), where we call memory_notify(MEM_GOING_OFFLINE, &arg) under mem_hotplug_begin(). mem_hotplug_begin() does a cpus_read_lock(). How does this even work or against which branch is this?
Hi David, On Mon, 16 Aug 2021 10:04:13 +0200 David Hildenbrand <david@redhat.com> wrote: > > On 16.08.21 09:46, qiang.zhang@windriver.com wrote: > > From: "Qiang.Zhang" <qiang.zhang@windriver.com> > > > > The flush_all_cpus_locked() should be called with cpus_read_lock/unlock(), > > ensure flush_cpu_slab() can be executed on schedule_on CPU. > > > > Fixes: 1c84f3c91640 ("mm, slub: fix memory and cpu hotplug related lock ordering issues") > > Which branch contains this commit? At least not linux.git or linux-next It is Andrew's mmotm which is included in linux-next but gets rebased often, so, for example, that SHA1 is no longer valid in linux-next today (is is now fd917c6407fb). This (unfortunately) make Fixes tags less useful for mmotm :-(
On 16.08.21 10:17, Stephen Rothwell wrote: > Hi David, > > On Mon, 16 Aug 2021 10:04:13 +0200 David Hildenbrand <david@redhat.com> wrote: >> >> On 16.08.21 09:46, qiang.zhang@windriver.com wrote: >>> From: "Qiang.Zhang" <qiang.zhang@windriver.com> >>> >>> The flush_all_cpus_locked() should be called with cpus_read_lock/unlock(), >>> ensure flush_cpu_slab() can be executed on schedule_on CPU. >>> >>> Fixes: 1c84f3c91640 ("mm, slub: fix memory and cpu hotplug related lock ordering issues") >> >> Which branch contains this commit? At least not linux.git or linux-next > > It is Andrew's mmotm which is included in linux-next but gets rebased Maybe I am blind or need more coffee: https://www.ozlabs.org/~akpm/mmotm/series > often, so, for example, that SHA1 is no longer valid in linux-next > today (is is now fd917c6407fb). > > This (unfortunately) make Fixes tags less useful for mmotm :-( Right, and it somewhat makes sense, because Andrew will actually squash patches before sending them further upstream. Ideally, such fixes should be discussed in the respective patch series, because before they go upstream, they are still under development.
On 8/16/21 10:04 AM, David Hildenbrand wrote: > On 16.08.21 09:46, qiang.zhang@windriver.com wrote: >> From: "Qiang.Zhang" <qiang.zhang@windriver.com> >> >> The flush_all_cpus_locked() should be called with cpus_read_lock/unlock(), >> ensure flush_cpu_slab() can be executed on schedule_on CPU. >> >> Fixes: 1c84f3c91640 ("mm, slub: fix memory and cpu hotplug related lock ordering issues") > Memory notifiers are getting called from online_pages()/offline_pages(), > where we call memory_notify(MEM_GOING_OFFLINE, &arg) under > mem_hotplug_begin(). > > mem_hotplug_begin() does a cpus_read_lock(). Exactly. Also flush_all_cpus_locked() has a lockdep assert for cpus_read_lock() which doesn't trigger in testing. > How does this even work or against which branch is this? >
diff --git a/mm/slub.c b/mm/slub.c index 5543d57cb128..cf3f93abbd3e 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4593,12 +4593,14 @@ static int slab_mem_going_offline_callback(void *arg) { struct kmem_cache *s; + cpus_read_lock(); mutex_lock(&slab_mutex); list_for_each_entry(s, &slab_caches, list) { flush_all_cpus_locked(s); __kmem_cache_do_shrink(s); } mutex_unlock(&slab_mutex); + cpus_read_unlock(); return 0; }