• Russell King's avatar
    ARM: lockdep: fix unannotated irqs-on · ac78884e
    Russell King authored
    CPU: Testing write buffer coherency: ok
    ------------[ cut here ]------------
    WARNING: at kernel/lockdep.c:3145 check_flags+0xcc/0x1dc()
    Modules linked in:
    [<c0035120>] (unwind_backtrace+0x0/0xf8) from [<c0355374>] (dump_stack+0x20/0x24)
    [<c0355374>] (dump_stack+0x20/0x24) from [<c0060c04>] (warn_slowpath_common+0x58/0x70)
    [<c0060c04>] (warn_slowpath_common+0x58/0x70) from [<c0060c3c>] (warn_slowpath_null+0x20/0x24)
    [<c0060c3c>] (warn_slowpath_null+0x20/0x24) from [<c008f224>] (check_flags+0xcc/0x1dc)
    [<c008f224>] (check_flags+0xcc/0x1dc) from [<c00945dc>] (lock_acquire+0x50/0x140)
    [<c00945dc>] (lock_acquire+0x50/0x140) from [<c0358434>] (_raw_spin_lock+0x50/0x88)
    [<c0358434>] (_raw_spin_lock+0x50/0x88) from [<c00fd114>] (set_task_comm+0x2c/0x60)
    [<c00fd114>] (set_task_comm+0x2c/0x60) from [<c007e184>] (kthreadd+0x30/0x108)
    [<c007e184>] (kthreadd+0x30/0x108) from [<c0030104>] (kernel_thread_exit+0x0/0x8)
    ---[ end trace 1b75b31a2719ed1c ]---
    possible reason: unannotated irqs-on.
    irq event stamp: 3
    hardirqs last  enabled at (2): [<c0059bb0>] finish_task_switch+0x48/0xb0
    hardirqs last disabled at (3): [<c002f0b0>] ret_slow_syscall+0xc/0x1c
    softirqs last  enabled at (0): [<c005f3e0>] copy_process+0x394/0xe5c
    softirqs last disabled at (0): [<(null)>] (null)
    
    Fix this by ensuring that the lockdep interrupt state is manipulated in
    the appropriate places.  We essentially treat userspace as an entirely
    separate environment which isn't relevant to lockdep (lockdep doesn't
    monitor userspace.)  We don't tell lockdep that IRQs will be enabled
    in that environment.
    
    Instead, when creating kernel threads (which is a rare event compared
    to entering/leaving userspace) we have to update the lockdep state.  Do
    this by starting threads with IRQs disabled, and in the kthread helper,
    tell lockdep that IRQs are enabled, and enable them.
    
    This provides lockdep with a consistent view of the current IRQ state
    in kernel space.
    
    This also revert portions of 0d928b0b
    which didn't fix the problem.
    Tested-by: default avatarMing Lei <tom.leiming@gmail.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    ac78884e
process.c 9.84 KB