Re: [PATCH RT 2/2][RFC] let RCU stall messages escape with CONFIG_PREEMPT_RT_FULL
From: Paul E. McKenney <hidden>
Date: 2012-12-10 14:29:24
Also in:
linux-arm-kernel, lkml
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 <redacted>
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
quoted hunk ↗ jump to hunk
--- 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; #endifIndex: 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 +