On Tue, Dec 04, 2012 at 08:52:21PM -0800, Frank Rowand wrote:
>
> The printk()s in RCU stall warnings do not get flushed to the console
> on ARM. Add the oops_in_progress flag back into the special trylock case in
> console_trylock_for_printk(), and set the flag using "bust_spinlocks(1)".
> This allows the printk() output to be flushed to the console.
>
> Signed-off-by: Frank Rowand <frank.row...@am.sony.com>
Is bust_spinlocks(1) appropriate for all architectures, or should this
be conditioned on architectures that need oops_in_progress to be set?
Thanx, Paul
> ---
> kernel/printk.c | 5 3 + 2 - 0 !
> kernel/rcutree.c | 14 14 + 0 - 0 !
> 2 files changed, 17 insertions(+), 2 deletions(-)
>
> Index: b/kernel/printk.c
> ===================================================================
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -1390,8 +1390,9 @@ static int console_trylock_for_printk(un
> {
> int retval = 0, wake = 0;
> #ifdef CONFIG_PREEMPT_RT_FULL
> - int lock = !early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
> - (preempt_count() <= 1);
> + int lock = oops_in_progress || (
> + !early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
> + (preempt_count() <= 1));
> #else
> int lock = 1;
> #endif
> Index: b/kernel/rcutree.c
> ===================================================================
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -758,6 +758,11 @@ static void print_other_cpu_stall(struct
> raw_spin_unlock_irqrestore(&rnp->lock, flags);
>
> /*
> + * Allow printk() to flush to device
> + */
> + bust_spinlocks(1);
> +
> + /*
> * OK, time to rat on our buddy...
> * See Documentation/RCU/stallwarn.txt for info on how to debug
> * RCU CPU stall warnings.
> @@ -799,6 +804,8 @@ static void print_other_cpu_stall(struct
>
> rcu_print_detail_task_stall(rsp);
>
> + bust_spinlocks(0);
> +
> force_quiescent_state(rsp, 0); /* Kick them all. */
> }
>
> @@ -808,6 +815,11 @@ static void print_cpu_stall(struct rcu_s
> struct rcu_node *rnp = rcu_get_root(rsp);
>
> /*
> + * Allow printk() to flush to device
> + */
> + bust_spinlocks(1);
> +
> + /*
> * OK, time to rat on ourselves...
> * See Documentation/RCU/stallwarn.txt for info on how to debug
> * RCU CPU stall warnings.
> @@ -820,6 +832,8 @@ static void print_cpu_stall(struct rcu_s
> if (!trigger_all_cpu_backtrace())
> dump_stack();
>
> + bust_spinlocks(0);
> +
> raw_spin_lock_irqsave(&rnp->lock, flags);
> if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
> rsp->jiffies_stall = jiffies +
>
--
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