From 1efc5da3cf567d2f6b795f9d2112ed97fec4ee7c Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 10 Feb 2007 01:46:29 -0800 Subject: [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 Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/printk.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/printk.c b/kernel/printk.c index 4da26b067976..0c151877ff71 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -529,7 +529,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) zap_locks(); /* This stops the holder of console_sem just where we want him */ - local_irq_save(flags); + raw_local_irq_save(flags); lockdep_off(); spin_lock(&logbuf_lock); printk_cpu = smp_processor_id(); @@ -618,7 +618,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) up(&console_sem); } lockdep_on(); - local_irq_restore(flags); + raw_local_irq_restore(flags); } else { /* * Someone else owns the drivers. We drop the spinlock, which @@ -628,7 +628,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) printk_cpu = UINT_MAX; spin_unlock(&logbuf_lock); lockdep_on(); - local_irq_restore(flags); + raw_local_irq_restore(flags); } preempt_enable(); -- cgit v1.2.3