Messages in this thread Patch in this message | | | Date | Tue, 14 Feb 2012 15:40:36 +0800 | From | Yong Zhang <> | Subject | Re: [PATCH] percpu: use raw_local_irq_* in _this_cpu op |
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On Tue, Feb 14, 2012 at 11:30:06AM +0800, Ming Lei wrote: > Hi, > > On Tue, Feb 14, 2012 at 1:23 AM, Tejun Heo <tj@kernel.org> wrote: > > On Mon, Feb 13, 2012 at 07:03:38PM +0800, Ming Lei wrote: > >> It doesn't make sense to trace irq off or do irq flags > >> lock proving inside 'this_cpu' operations, so replace local_irq_* > >> with raw_local_irq_* in 'this_cpu' op. > >> > >> Also the patch fixes one lockdep warning[1], which is caused > >> by the added local_irq_save/restore(flags) in this_cpu_inc > >> called by __debug_atomic_inc: kernel/lockdep.c > > > > I think this isn't gonna hurt anything but I don't understand why the > > lockdep warning is triggering when using traced version. ?Can you > > please explain that in a bit more detail in the patch description? > > In trace_hardirqs_on_caller:kernel/lockdep.c, __debug_atomic_inc > will be called to add on 'this_cpu' variable, so may introduce recursive > trace_hardirqs_on|off_caller called.
Don't we need to prevent this kind of recursion first?
UNTESTED patch, I guess it'll smooth your concern. --- diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 8889f7d..028b4c5 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -2561,6 +2561,8 @@ void trace_hardirqs_on_caller(unsigned long ip) if (unlikely(!debug_locks || current->lockdep_recursion)) return; + current->lockdep_recursion = 1; + if (unlikely(current->hardirqs_enabled)) { /* * Neither irq nor preemption are disabled here @@ -2568,7 +2570,7 @@ void trace_hardirqs_on_caller(unsigned long ip) * in a stat is not a big deal. */ __debug_atomic_inc(redundant_hardirqs_on); - return; + goto out; } /* @@ -2577,23 +2579,24 @@ void trace_hardirqs_on_caller(unsigned long ip) * enabled.. someone messed up their IRQ state tracing. */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) - return; + goto out; /* * See the fine text that goes along with this variable definition. */ if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled))) - return; + goto out; /* * Can't allow enabling interrupts while in an interrupt handler, * that's general bad form and such. Recursion, limited stack etc.. */ if (DEBUG_LOCKS_WARN_ON(current->hardirq_context)) - return; + goto out; - current->lockdep_recursion = 1; __trace_hardirqs_on_caller(ip); + +out: current->lockdep_recursion = 0; } EXPORT_SYMBOL(trace_hardirqs_on_caller);
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