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authorMathieu Desnoyers <compudj@krystal.dyndns.org>2007-02-10 01:46:29 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-11 11:18:06 -0800
commit1efc5da3cf567d2f6b795f9d2112ed97fec4ee7c (patch)
tree25a45ed5a45e5ad54c6264240cd3c55e751858b3 /Documentation/rtc.txt
parent482a579b370a0bf924b577efd6c750284a95e0fb (diff)
downloadlinux-linaro-stable-1efc5da3cf567d2f6b795f9d2112ed97fec4ee7c.tar.gz
[PATCH] order of lockdep off/on in vprintk() should be changed
The order of locking between lockdep_off/on() and local_irq_save/restore() in vprintk() should be changed. * In kernel/printk.c : vprintk() does : preempt_disable() local_irq_save() lockdep_off() spin_lock(&logbuf_lock) spin_unlock(&logbuf_lock) if(!down_trylock(&console_sem)) up(&console_sem) lockdep_on() local_irq_restore() preempt_enable() The goals here is to make sure we do not call printk() recursively from kernel/lockdep.c:__lock_acquire() (called from spin_* and down/up) nor from kernel/lockdep.c:trace_hardirqs_on/off() (called from local_irq_restore/save). It can then potentially call printk() through mark_held_locks/mark_lock. It correctly protects against the spin_lock call and the up/down call, but it does not protect against local_irq_restore. It could cause infinite recursive printk/trace_hardirqs_on() calls when printk() is called from the mark_lock() error handing path. We should change the locking so it becomes correct : preempt_disable() lockdep_off() local_irq_save() spin_lock(&logbuf_lock) spin_unlock(&logbuf_lock) if(!down_trylock(&console_sem)) up(&console_sem) local_irq_restore() lockdep_on() preempt_enable() Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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