The patch titled
ksm: annotate ksm_thread_mutex is no deadlock source
has been removed from the -mm tree. Its filename was
ksm-annotate-ksm_thread_mutex-is-no-deadlock-source.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: ksm: annotate ksm_thread_mutex is no deadlock source
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
commit 62b61f611e ("ksm: memory hotremove migration only") caused the
following new lockdep warning.
=======================================================
[ INFO: possible circular locking dependency detected ]
-------------------------------------------------------
bash/1621 is trying to acquire lock:
((memory_chain).rwsem){.+.+.+}, at: [<ffffffff81079339>]
__blocking_notifier_call_chain+0x69/0xc0
but task is already holding lock:
(ksm_thread_mutex){+.+.+.}, at: [<ffffffff8113a3aa>]
ksm_memory_callback+0x3a/0xc0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (ksm_thread_mutex){+.+.+.}:
[<ffffffff8108b70a>] lock_acquire+0xaa/0x140
[<ffffffff81505d74>] __mutex_lock_common+0x44/0x3f0
[<ffffffff81506228>] mutex_lock_nested+0x48/0x60
[<ffffffff8113a3aa>] ksm_memory_callback+0x3a/0xc0
[<ffffffff8150c21c>] notifier_call_chain+0x8c/0xe0
[<ffffffff8107934e>] __blocking_notifier_call_chain+0x7e/0xc0
[<ffffffff810793a6>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff813afbfb>] memory_notify+0x1b/0x20
[<ffffffff81141b7c>] remove_memory+0x1cc/0x5f0
[<ffffffff813af53d>] memory_block_change_state+0xfd/0x1a0
[<ffffffff813afd62>] store_mem_state+0xe2/0xf0
[<ffffffff813a0bb0>] sysdev_store+0x20/0x30
[<ffffffff811bc116>] sysfs_write_file+0xe6/0x170
[<ffffffff8114f398>] vfs_write+0xc8/0x190
[<ffffffff8114fc14>] sys_write+0x54/0x90
[<ffffffff810028b2>] system_call_fastpath+0x16/0x1b
-> #0 ((memory_chain).rwsem){.+.+.+}:
[<ffffffff8108b5ba>] __lock_acquire+0x155a/0x1600
[<ffffffff8108b70a>] lock_acquire+0xaa/0x140
[<ffffffff81506601>] down_read+0x51/0xa0
[<ffffffff81079339>] __blocking_notifier_call_chain+0x69/0xc0
[<ffffffff810793a6>] blocking_notifier_call_chain+0x16/0x20
[<ffffffff813afbfb>] memory_notify+0x1b/0x20
[<ffffffff81141f1e>] remove_memory+0x56e/0x5f0
[<ffffffff813af53d>] memory_block_change_state+0xfd/0x1a0
[<ffffffff813afd62>] store_mem_state+0xe2/0xf0
[<ffffffff813a0bb0>] sysdev_store+0x20/0x30
[<ffffffff811bc116>] sysfs_write_file+0xe6/0x170
[<ffffffff8114f398>] vfs_write+0xc8/0x190
[<ffffffff8114fc14>] sys_write+0x54/0x90
[<ffffffff810028b2>] system_call_fastpath+0x16/0x1b
But it's a false positive. Both memory_chain.rwsem and ksm_thread_mutex
have an outer lock (mem_hotplug_mutex). So they cannot deadlock.
Thus, This patch annotate ksm_thread_mutex is not deadlock source.
[akpm@xxxxxxxxxxxxxxxxxxxx: update comment, from Hugh]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN mm/ksm.c~ksm-annotate-ksm_thread_mutex-is-no-deadlock-source mm/ksm.c
--- a/mm/ksm.c~ksm-annotate-ksm_thread_mutex-is-no-deadlock-source
+++ a/mm/ksm.c
@@ -1724,8 +1724,13 @@ static int ksm_memory_callback(struct no
/*
* Keep it very simple for now: just lock out ksmd and
* MADV_UNMERGEABLE while any memory is going offline.
+ * mutex_lock_nested() is necessary because lockdep was alarmed
+ * that here we take ksm_thread_mutex inside notifier chain
+ * mutex, and later take notifier chain mutex inside
+ * ksm_thread_mutex to unlock it. But that's safe because both
+ * are inside mem_hotplug_mutex.
*/
- mutex_lock(&ksm_thread_mutex);
+ mutex_lock_nested(&ksm_thread_mutex, SINGLE_DEPTH_NESTING);
break;
case MEM_OFFLINE:
_
Patches currently in -mm which might be from kosaki.motohiro@xxxxxxxxxxxxxx are
linux-next.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-update.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-fix-set_pgdat_percpu_threshold-dont-use-for_each_online_cpu.patch
writeback-io-less-balance_dirty_pages.patch
writeback-consolidate-variable-names-in-balance_dirty_pages.patch
writeback-per-task-rate-limit-on-balance_dirty_pages.patch
writeback-per-task-rate-limit-on-balance_dirty_pages-fix.patch
writeback-prevent-duplicate-balance_dirty_pages_ratelimited-calls.patch
writeback-account-per-bdi-accumulated-written-pages.patch
writeback-bdi-write-bandwidth-estimation.patch
writeback-bdi-write-bandwidth-estimation-fix.patch
writeback-show-bdi-write-bandwidth-in-debugfs.patch
writeback-quit-throttling-when-bdi-dirty-pages-dropped-low.patch
writeback-reduce-per-bdi-dirty-threshold-ramp-up-time.patch
writeback-make-reasonable-gap-between-the-dirty-background-thresholds.patch
writeback-scale-down-max-throttle-bandwidth-on-concurrent-dirtiers.patch
writeback-add-trace-event-for-balance_dirty_pages.patch
writeback-make-nr_to_write-a-per-file-limit.patch
writeback-make-nr_to_write-a-per-file-limit-fix.patch
vmscan-factor-out-kswapd-sleeping-logic-from-kswapd.patch
mm-compaction-add-trace-events-for-memory-compaction-activity.patch
mm-vmscan-convert-lumpy_mode-into-a-bitmask.patch
mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim.patch
mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim-fix.patch
mm-migration-allow-migration-to-operate-asynchronously-and-avoid-synchronous-compaction-in-the-faster-path.patch
mm-migration-allow-migration-to-operate-asynchronously-and-avoid-synchronous-compaction-in-the-faster-path-fix.patch
mm-migration-cleanup-migrate_pages-api-by-matching-types-for-offlining-and-sync.patch
mm-compaction-perform-a-faster-migration-scan-when-migrating-asynchronously.patch
mm-vmscan-rename-lumpy_mode-to-reclaim_mode.patch
mm-deactivate-invalidated-pages.patch
mm-deactivate-invalidated-pages-fix.patch
oom-allow-a-non-cap_sys_resource-proces-to-oom_score_adj-down.patch
do_wp_page-remove-the-reuse-flag.patch
do_wp_page-clarify-dirty_page-handling.patch
mlock-avoid-dirtying-pages-and-triggering-writeback.patch
kmsg_dump-add-kmsg_dump-calls-to-the-reboot-halt-poweroff-and-emergency_restart-paths.patch
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