diff options
author | David Rientjes <rientjes@google.com> | 2015-04-15 01:45:11 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-15 02:49:00 +0300 |
commit | 30467e0b3be83c286d60039f8267dd421128ca74 (patch) | |
tree | abda19f050d5dd049a31728d005fbef5c7987e41 /include/linux/memory_hotplug.h | |
parent | 17e0db822b00cff96c1b662ac0dc0449cb70e0ec (diff) | |
download | linux-30467e0b3be83c286d60039f8267dd421128ca74.tar.xz |
mm, hotplug: fix concurrent memory hot-add deadlock
There's a deadlock when concurrently hot-adding memory through the probe
interface and switching a memory block from offline to online.
When hot-adding memory via the probe interface, add_memory() first takes
mem_hotplug_begin() and then device_lock() is later taken when registering
the newly initialized memory block. This creates a lock dependency of (1)
mem_hotplug.lock (2) dev->mutex.
When switching a memory block from offline to online, dev->mutex is first
grabbed in device_online() when the write(2) transitions an existing
memory block from offline to online, and then online_pages() will take
mem_hotplug_begin().
This creates a lock inversion between mem_hotplug.lock and dev->mutex.
Vitaly reports that this deadlock can happen when kworker handling a probe
event races with systemd-udevd switching a memory block's state.
This patch requires the state transition to take mem_hotplug_begin()
before dev->mutex. Hot-adding memory via the probe interface creates a
memory block while holding mem_hotplug_begin(), there is no way to take
dev->mutex first in this case.
online_pages() and offline_pages() are only called when transitioning
memory block state. We now require that mem_hotplug_begin() is taken
before calling them -- this requires exporting the mem_hotplug_begin() and
mem_hotplug_done() to generic code. In all hot-add and hot-remove cases,
mem_hotplug_begin() is done prior to device_online(). This is all that is
needed to avoid the deadlock.
Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhang Zhen <zhenzhang.zhang@huawei.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/memory_hotplug.h')
-rw-r--r-- | include/linux/memory_hotplug.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 8f1a41951df9..6ffa0ac7f7d6 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -192,6 +192,9 @@ extern void get_page_bootmem(unsigned long ingo, struct page *page, void get_online_mems(void); void put_online_mems(void); +void mem_hotplug_begin(void); +void mem_hotplug_done(void); + #else /* ! CONFIG_MEMORY_HOTPLUG */ /* * Stub functions for when hotplug is off @@ -231,6 +234,9 @@ static inline int try_online_node(int nid) static inline void get_online_mems(void) {} static inline void put_online_mems(void) {} +static inline void mem_hotplug_begin(void) {} +static inline void mem_hotplug_done(void) {} + #endif /* ! CONFIG_MEMORY_HOTPLUG */ #ifdef CONFIG_MEMORY_HOTREMOVE |