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2b4bc78956
As load_current_idt() is now what is used to update the IDT for the switches needed for NMI, lockdep debug, and for tracing, it must not call local_irq_save(). This is because one of the users of this is lockdep, which does tracing of local_irq_save() and when the debug trap is hit, we need to update the IDT before tracing interrupts being disabled. As load_current_idt() is used to do this, calling local_irq_save() which lockdep traces, defeats the point of calling load_current_idt(). As interrupts are already disabled when used by lockdep and NMI, the only other user is tracing that can disable interrupts itself. Simply have the tracing update disable interrupts before calling load_current_idt() instead of breaking the other users. Here's the dump that happened: ------------[ cut here ]------------ WARNING: at /work/autotest/nobackup/linux-test.git/kernel/fork.c:1196 copy_process+0x2c3/0x1398() DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled) Modules linked in: CPU: 1 PID: 4570 Comm: gdm-simple-gree Not tainted 3.10.0-rc3-test+ #5 Hardware name: /DG965MQ, BIOS MQ96510J.86A.0372.2006.0605.1717 06/05/2006 ffffffff81d2a7a5 ffff88006ed13d50 ffffffff8192822b ffff88006ed13d90 ffffffff81035f25 ffff8800721c6000 ffff88006ed13da0 0000000001200011 0000000000000000 ffff88006ed5e000 ffff8800721c6000 ffff88006ed13df0 Call Trace: [<ffffffff8192822b>] dump_stack+0x19/0x1b [<ffffffff81035f25>] warn_slowpath_common+0x67/0x80 [<ffffffff81035fe1>] warn_slowpath_fmt+0x46/0x48 [<ffffffff812bfc5d>] ? __raw_spin_lock_init+0x31/0x52 [<ffffffff810341f7>] copy_process+0x2c3/0x1398 [<ffffffff8103539d>] do_fork+0xa8/0x260 [<ffffffff810ca7b1>] ? trace_preempt_on+0x2a/0x2f [<ffffffff812afb3e>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff81937fe7>] ? sysret_check+0x1b/0x56 [<ffffffff81937fe7>] ? sysret_check+0x1b/0x56 [<ffffffff810355cf>] SyS_clone+0x16/0x18 [<ffffffff81938369>] stub_clone+0x69/0x90 [<ffffffff81937fc2>] ? system_call_fastpath+0x16/0x1b ---[ end trace 8b157a9d20ca1aa2 ]--- in fork.c: #ifdef CONFIG_PROVE_LOCKING DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); <-- bug here DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); #endif Cc: Seiji Aguchi <seiji.aguchi@hds.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> |
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