• Ingo Molnar's avatar
    x86: fix deadlock, make pgd_lock irq-safe · 58d5d0d8
    Ingo Molnar authored
    lockdep just caught this one:
    
    =================================
    [ INFO: inconsistent lock state ]
    2.6.24 #38
    ---------------------------------
    inconsistent {in-softirq-W} -> {softirq-on-W} usage.
    swapper/1 [HC0[0]:SC0[0]:HE1:SE1] takes:
     (pgd_lock){-+..}, at: [<ffffffff8022a9ea>] mm_init+0x1da/0x250
    {in-softirq-W} state was registered at:
      [<ffffffffffffffff>] 0xffffffffffffffff
    irq event stamp: 394559
    hardirqs last  enabled at (394559): [<ffffffff80267f0a>] get_page_from_freelist+0x30a/0x4c0
    hardirqs last disabled at (394558): [<ffffffff80267d25>] get_page_from_freelist+0x125/0x4c0
    softirqs last  enabled at (393952): [<ffffffff80232f8e>] __do_softirq+0xce/0xe0
    softirqs last disabled at (393945): [<ffffffff8020c57c>] call_softirq+0x1c/0x30
    
    other info that might help us debug this:
    no locks held by swapper/1.
    
    stack backtrace:
    Pid: 1, comm: swapper Not tainted 2.6.24 #38
    
    Call Trace:
     [<ffffffff8024e1fb>] print_usage_bug+0x18b/0x190
     [<ffffffff8024f55d>] mark_lock+0x53d/0x560
     [<ffffffff8024fffa>] __lock_acquire+0x3ca/0xed0
     [<ffffffff80250ba8>] lock_acquire+0xa8/0xe0
     [<ffffffff8022a9ea>] ? mm_init+0x1da/0x250
     [<ffffffff809bcd10>] _spin_lock+0x30/0x70
     [<ffffffff8022a9ea>] mm_init+0x1da/0x250
     [<ffffffff8022aa99>] mm_alloc+0x39/0x50
     [<ffffffff8028b95a>] bprm_mm_init+0x2a/0x1a0
     [<ffffffff8028d12b>] do_execve+0x7b/0x220
     [<ffffffff80209776>] sys_execve+0x46/0x70
     [<ffffffff8020c214>] kernel_execve+0x64/0xd0
     [<ffffffff8020901e>] ? _stext+0x1e/0x20
     [<ffffffff802090ba>] init_post+0x9a/0xf0
     [<ffffffff809bc5f6>] ? trace_hardirqs_on_thunk+0x35/0x3a
     [<ffffffff8024f75a>] ? trace_hardirqs_on+0xba/0xd0
     [<ffffffff8020c1a8>] ? child_rip+0xa/0x12
     [<ffffffff8020bcbc>] ? restore_args+0x0/0x44
     [<ffffffff8020c19e>] ? child_rip+0x0/0x12
    
    turns out that pgd_lock has been used on 64-bit x86 in an irq-unsafe
    way for almost two years, since commit 8c914cb7.
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    58d5d0d8
fault.c 24.5 KB