diff options
| author | Mathieu Desnoyers <compudj@krystal.dyndns.org> | 2007-02-10 01:46:29 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-11 11:18:06 -0800 |
| commit | 1efc5da3cf567d2f6b795f9d2112ed97fec4ee7c (patch) | |
| tree | 25a45ed5a45e5ad54c6264240cd3c55e751858b3 | |
| parent | 482a579b370a0bf924b577efd6c750284a95e0fb (diff) | |
[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>
| -rw-r--r-- | kernel/printk.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index 4da26b06797..0c151877ff7 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(); |