• Heiko Carstens's avatar
    mm: take memory hotplug lock within numa_zonelist_order_handler() · 167d0f25
    Heiko Carstens authored
    Andre Wild reported the following warning:
    
      WARNING: CPU: 2 PID: 1205 at kernel/cpu.c:240 lockdep_assert_cpus_held+0x4c/0x60
      Modules linked in:
      CPU: 2 PID: 1205 Comm: bash Not tainted 4.13.0-rc2-00022-gfd2b2c57 #10
      Hardware name: IBM 2964 N96 702 (z/VM 6.4.0)
      task: 00000000701d8100 task.stack: 0000000073594000
      Krnl PSW : 0704f00180000000 0000000000145e24 (lockdep_assert_cpus_held+0x4c/0x60)
      ...
      Call Trace:
       lockdep_assert_cpus_held+0x42/0x60)
       stop_machine_cpuslocked+0x62/0xf0
       build_all_zonelists+0x92/0x150
       numa_zonelist_order_handler+0x102/0x150
       proc_sys_call_handler.isra.12+0xda/0x118
       proc_sys_write+0x34/0x48
       __vfs_write+0x3c/0x178
       vfs_write+0xbc/0x1a0
       SyS_write+0x66/0xc0
       system_call+0xc4/0x2b0
       locks held by bash/1205:
       #0:  (sb_writers#4){.+.+.+}, at: vfs_write+0xa6/0x1a0
       #1:  (zl_order_mutex){+.+...}, at: numa_zonelist_order_handler+0x44/0x150
       #2:  (zonelists_mutex){+.+...}, at: numa_zonelist_order_handler+0xf4/0x150
      Last Breaking-Event-Address:
        lockdep_assert_cpus_held+0x48/0x60
    
    This can be easily triggered with e.g.
    
        echo n > /proc/sys/vm/numa_zonelist_order
    
    In commit 3f906ba2 ("mm/memory-hotplug: switch locking to a percpu
    rwsem") memory hotplug locking was changed to fix a potential deadlock.
    
    This also switched the stop_machine() invocation within
    build_all_zonelists() to stop_machine_cpuslocked() which now expects
    that online cpus are locked when being called.
    
    This assumption is not true if build_all_zonelists() is being called
    from numa_zonelist_order_handler().
    
    In order to fix this simply add a mem_hotplug_begin()/mem_hotplug_done()
    pair to numa_zonelist_order_handler().
    
    Link: http://lkml.kernel.org/r/20170726111738.38768-1-heiko.carstens@de.ibm.com
    Fixes: 3f906ba2 ("mm/memory-hotplug: switch locking to a percpu rwsem")
    Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
    Reported-by: default avatarAndre Wild <wild@linux.vnet.ibm.com>
    Acked-by: default avatarMichal Hocko <mhocko@suse.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    167d0f25
page_alloc.c 213 KB