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authorRussell King <rmk+kernel@arm.linux.org.uk>2010-07-10 05:10:18 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-07-10 05:53:13 -0400
commitac78884e6d89714d18b32b5b7d574116ecfb7c88 (patch)
tree4e2d9d3106f10f5ce7ae3c9469444cab8ec75024 /Documentation/input/input.txt
parentd9e38040ccf9eb06b9b41c393c512ceb23f51a7f (diff)
ARM: lockdep: fix unannotated irqs-on
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 0d928b0b616d1c5c5fe76019a87cba171ca91633 which didn't fix the problem. Tested-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'Documentation/input/input.txt')
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