On Mon, 13 Mar 2017 18:08:48 +0800
Qi Hou <qi....@windriver.com> wrote:
> The current order of calls within trace_hardirqs_off() would provoke an
> "unannotated irqs-off" WARNING.
>
> This warning was reported by check_flags() when it found that the hardirqs has
> been disabled but the irq-flags state, hardirqs_enabled, has not been cleared.
>
> Check_flags() is called via trace_hardirqs_off(), and trace_hardirqs_off()
> will
> be called by functions kind of local_irq_disable() if CONFIG_TRACE_IRQFLAGS
> has
> been enabled.
>
> The calltrace from functions kind of local_irq_diasble() to check_flags()
> simplied as below:
>
> local_irq_disable()
> |- trace_hardirqs_off()
> |- trace_hardirqs_off_caller()
> |- preemptirqsoff_hist()
There is no preemptirqsoff_hist() function in the kernel.
-- Steve
> |- __DO_TRACE()
> |- rcu_dereference_sched()
> |- rcu_read_lock_sched_held()
> |- lock_is_held()
> |- check_flags()
>
> The order of calls within trace_hardirqs_off() can be simplified as below:
>
> local_irq_disable()
> |- raw_local_irq_disable()
> |- trace_hardirqs_off()
> |- trace_hardirqs_off() --> check_flags()
> |- hardirqs_enabled = 0
>
> We could find that the call to check_flags() has been made between disabling
> hardirqs and clearing hardirqs_enabled. That will definitely cause an
> "unannotated irqs-off" warning.
>
> To fix this "unannotated irqs-off" warning, we must call trace_hardirqs_off()
> after that we clear hardirqs_enabled.
>
> Signed-off-by: Qi Hou <qi....@windriver.com>
> ---
> kernel/locking/lockdep.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 577f026..e8b35e4 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -2627,8 +2627,6 @@ __visible void trace_hardirqs_off_caller(unsigned long
> ip)
> {
> struct task_struct *curr = current;
>
> - time_hardirqs_off(CALLER_ADDR0, ip);
> -
> if (unlikely(!debug_locks || current->lockdep_recursion))
> return;
>
> @@ -2649,6 +2647,8 @@ __visible void trace_hardirqs_off_caller(unsigned long
> ip)
> debug_atomic_inc(hardirqs_off_events);
> } else
> debug_atomic_inc(redundant_hardirqs_off);
> +
> + time_hardirqs_off(CALLER_ADDR0, ip);
> }
> EXPORT_SYMBOL(trace_hardirqs_off_caller);
>
