Setting a memory block offline triggers the following lockdep warning. This looks exactly like the issue reported by Kosaki Motohiro in https://lkml.org/lkml/2010/10/25/110. Seems like the resulting commit a0b0f58cdd did not fix the lockdep warning. I'm able to reproduce it with current 3.3.0-rc2 as well as 2.6.37-rc4-00147-ga0b0f58. I'm not familiar with lockdep annotations, but I tried using down_read_nested() for (memory_chain).rwsem, similar to the mutex_lock_nested() which was introduced for ksm_thread_mutex, but that didn't help. ====================================================== [ INFO: possible circular locking dependency detected ] 3.3.0-rc2 #8 Not tainted ------------------------------------------------------- sh/973 is trying to acquire lock: ((memory_chain).rwsem){.+.+.+}, at: [<000000000015b0e4>] __blocking_notifier_call_chain+0x40/0x8c but task is already holding lock: (ksm_thread_mutex/1){+.+.+.}, at: [<0000000000247484>] ksm_memory_callback+0x48/0xd0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (ksm_thread_mutex/1){+.+.+.}: [<0000000000195746>] __lock_acquire+0x47a/0xbd4 [<00000000001964b6>] lock_acquire+0xc2/0x148 [<00000000005dba62>] mutex_lock_nested+0x5a/0x354 [<0000000000247484>] ksm_memory_callback+0x48/0xd0 [<00000000005e1d4e>] notifier_call_chain+0x52/0x9c [<000000000015b0fa>] __blocking_notifier_call_chain+0x56/0x8c [<000000000015b15a>] blocking_notifier_call_chain+0x2a/0x3c [<00000000005d116e>] offline_pages.clone.21+0x17a/0x6f0 [<000000000046363a>] memory_block_change_state+0x172/0x2f4 [<0000000000463876>] store_mem_state+0xba/0xf0 [<00000000002e1592>] sysfs_write_file+0xf6/0x1a8 [<0000000000260d94>] vfs_write+0xb0/0x18c [<0000000000261108>] SyS_write+0x58/0xb4 [<00000000005dfab8>] sysc_noemu+0x22/0x28 [<000003fffcfa46c0>] 0x3fffcfa46c0 -> #0 ((memory_chain).rwsem){.+.+.+}: [<00000000001946ee>] validate_chain.clone.24+0x1106/0x11b4 [<0000000000195746>] __lock_acquire+0x47a/0xbd4 [<00000000001964b6>] lock_acquire+0xc2/0x148 [<00000000005dc30e>] down_read+0x4a/0x88 [<000000000015b0e4>] __blocking_notifier_call_chain+0x40/0x8c [<000000000015b15a>] blocking_notifier_call_chain+0x2a/0x3c [<00000000005d16be>] offline_pages.clone.21+0x6ca/0x6f0 [<000000000046363a>] memory_block_change_state+0x172/0x2f4 [<0000000000463876>] store_mem_state+0xba/0xf0 [<00000000002e1592>] sysfs_write_file+0xf6/0x1a8 [<0000000000260d94>] vfs_write+0xb0/0x18c [<0000000000261108>] SyS_write+0x58/0xb4 [<00000000005dfab8>] sysc_noemu+0x22/0x28 [<000003fffcfa46c0>] 0x3fffcfa46c0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ksm_thread_mutex/1); lock((memory_chain).rwsem); lock(ksm_thread_mutex/1); lock((memory_chain).rwsem); *** DEADLOCK *** 6 locks held by sh/973: #0: (&buffer->mutex){+.+.+.}, at: [<00000000002e14e6>] sysfs_write_file+0x4a/0x1a8 #1: (s_active#53){.+.+.+}, at: [<00000000002e156e>] sysfs_write_file+0xd2/0x1a8 #2: (&mem->state_mutex){+.+.+.}, at: [<000000000046350a>] memory_block_change_state+0x42/0x2f4 #3: (mem_hotplug_mutex){+.+.+.}, at: [<0000000000252e30>] lock_memory_hotplug+0x2c/0x4c #4: (pm_mutex#2){+.+.+.}, at: [<00000000005d10ea>] offline_pages.clone.21+0xf6/0x6f0 #5: (ksm_thread_mutex/1){+.+.+.}, at: [<0000000000247484>] ksm_memory_callback+0x48/0xd0 stack backtrace: CPU: 1 Not tainted 3.3.0-rc2 #8 Process sh (pid: 973, task: 000000003ecb8000, ksp: 000000003b24b898) 000000003b24b930 000000003b24b8b0 0000000000000002 0000000000000000. 000000003b24b950 000000003b24b8c8 000000003b24b8c8 00000000005da66a. 0000000000000000 0000000000000000 000000003b24ba08 000000003ecb8000. 000000000000000d 000000000000000c 000000003b24b918 0000000000000000. 0000000000000000 0000000000100af8 000000003b24b8b0 000000003b24b8f0. Call Trace: ([<0000000000100a06>] show_trace+0xee/0x144) [<0000000000192564>] print_circular_bug+0x220/0x328 [<00000000001946ee>] validate_chain.clone.24+0x1106/0x11b4 [<0000000000195746>] __lock_acquire+0x47a/0xbd4 [<00000000001964b6>] lock_acquire+0xc2/0x148 [<00000000005dc30e>] down_read+0x4a/0x88 [<000000000015b0e4>] __blocking_notifier_call_chain+0x40/0x8c [<000000000015b15a>] blocking_notifier_call_chain+0x2a/0x3c [<00000000005d16be>] offline_pages.clone.21+0x6ca/0x6f0 [<000000000046363a>] memory_block_change_state+0x172/0x2f4 [<0000000000463876>] store_mem_state+0xba/0xf0 [<00000000002e1592>] sysfs_write_file+0xf6/0x1a8 [<0000000000260d94>] vfs_write+0xb0/0x18c [<0000000000261108>] SyS_write+0x58/0xb4 [<00000000005dfab8>] sysc_noemu+0x22/0x28 [<000003fffcfa46c0>] 0x3fffcfa46c0 INFO: lockdep is turned off. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>