• Waiman Long's avatar
    debugobjects: Make kmemleak ignore debug objects · caba4cbb
    Waiman Long authored
    The allocated debug objects are either on the free list or in the
    hashed bucket lists. So they won't get lost. However if both debug
    objects and kmemleak are enabled and kmemleak scanning is done
    while some of the debug objects are transitioning from one list to
    the others, false negative reporting of memory leaks may happen for
    those objects. For example,
    
    [38687.275678] kmemleak: 12 new suspected memory leaks (see
    /sys/kernel/debug/kmemleak)
    unreferenced object 0xffff92e98aabeb68 (size 40):
      comm "ksmtuned", pid 4344, jiffies 4298403600 (age 906.430s)
      hex dump (first 32 bytes):
        00 00 00 00 00 00 00 00 d0 bc db 92 e9 92 ff ff  ................
        01 00 00 00 00 00 00 00 38 36 8a 61 e9 92 ff ff  ........86.a....
      backtrace:
        [<ffffffff8fa5378a>] kmemleak_alloc+0x4a/0xa0
        [<ffffffff8f47c019>] kmem_cache_alloc+0xe9/0x320
        [<ffffffff8f62ed96>] __debug_object_init+0x3e6/0x400
        [<ffffffff8f62ef01>] debug_object_activate+0x131/0x210
        [<ffffffff8f330d9f>] __call_rcu+0x3f/0x400
        [<ffffffff8f33117d>] call_rcu_sched+0x1d/0x20
        [<ffffffff8f4a183c>] put_object+0x2c/0x40
        [<ffffffff8f4a188c>] __delete_object+0x3c/0x50
        [<ffffffff8f4a18bd>] delete_object_full+0x1d/0x20
        [<ffffffff8fa535c2>] kmemleak_free+0x32/0x80
        [<ffffffff8f47af07>] kmem_cache_free+0x77/0x350
        [<ffffffff8f453912>] unlink_anon_vmas+0x82/0x1e0
        [<ffffffff8f440341>] free_pgtables+0xa1/0x110
        [<ffffffff8f44af91>] exit_mmap+0xc1/0x170
        [<ffffffff8f29db60>] mmput+0x80/0x150
        [<ffffffff8f2a7609>] do_exit+0x2a9/0xd20
    
    The references in the debug objects may also hide a real memory leak.
    
    As there is no point in having kmemleak to track debug object
    allocations, kmemleak checking is now disabled for debug objects.
    Signed-off-by: default avatarWaiman Long <longman@redhat.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Link: http://lkml.kernel.org/r/1502718733-8527-1-git-send-email-longman@redhat.com
    caba4cbb
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