Re: [PATCH v2 tip/core/rcu 02/11] lockdep: Use "WARNING" tag on lockdep splats

[Josh Triplett <josh@joshtriplett.org>]

On Mon, Apr 17, 2017 at 04:28:49PM -0700, Paul E. McKenney wrote:
> This commit changes lockdep splats to begin lines with "WARNING" and
> to use pr_warn() instead of printk().  This change eases scripted
> analysis of kernel console output.
> 
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Reported-by: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Acked-by: Dmitry Vyukov <dvyukov@google.com>

Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Any reason not to change the adjacent calls to printk (without a
priority) to pr_warn?

>  kernel/locking/lockdep.c       | 86 +++++++++++++++++++++---------------------
>  kernel/locking/rtmutex-debug.c |  9 +++--
>  2 files changed, 48 insertions(+), 47 deletions(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index a95e5d1f4a9c..e9d4f85b290c 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -1144,10 +1144,10 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth,
>  		return 0;
>  
>  	printk("\n");
> -	printk("======================================================\n");
> -	printk("[ INFO: possible circular locking dependency detected ]\n");
> +	pr_warn("======================================================\n");
> +	pr_warn("WARNING: possible circular locking dependency detected\n");
>  	print_kernel_ident();
> -	printk("-------------------------------------------------------\n");
> +	pr_warn("------------------------------------------------------\n");
>  	printk("%s/%d is trying to acquire lock:\n",
>  		curr->comm, task_pid_nr(curr));
>  	print_lock(check_src);
> @@ -1482,11 +1482,11 @@ print_bad_irq_dependency(struct task_struct *curr,
>  		return 0;
>  
>  	printk("\n");
> -	printk("======================================================\n");
> -	printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
> +	pr_warn("=====================================================\n");
> +	pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
>  		irqclass, irqclass);
>  	print_kernel_ident();
> -	printk("------------------------------------------------------\n");
> +	pr_warn("-----------------------------------------------------\n");
>  	printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
>  		curr->comm, task_pid_nr(curr),
>  		curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
> @@ -1711,10 +1711,10 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
>  		return 0;
>  
>  	printk("\n");
> -	printk("=============================================\n");
> -	printk("[ INFO: possible recursive locking detected ]\n");
> +	pr_warn("============================================\n");
> +	pr_warn("WARNING: possible recursive locking detected\n");
>  	print_kernel_ident();
> -	printk("---------------------------------------------\n");
> +	pr_warn("--------------------------------------------\n");
>  	printk("%s/%d is trying to acquire lock:\n",
>  		curr->comm, task_pid_nr(curr));
>  	print_lock(next);
> @@ -2061,10 +2061,10 @@ static void print_collision(struct task_struct *curr,
>  			struct lock_chain *chain)
>  {
>  	printk("\n");
> -	printk("======================\n");
> -	printk("[chain_key collision ]\n");
> +	pr_warn("============================\n");
> +	pr_warn("WARNING: chain_key collision\n");
>  	print_kernel_ident();
> -	printk("----------------------\n");
> +	pr_warn("----------------------------\n");
>  	printk("%s/%d: ", current->comm, task_pid_nr(current));
>  	printk("Hash chain already cached but the contents don't match!\n");
>  
> @@ -2360,10 +2360,10 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
>  		return 0;
>  
>  	printk("\n");
> -	printk("=================================\n");
> -	printk("[ INFO: inconsistent lock state ]\n");
> +	pr_warn("================================\n");
> +	pr_warn("WARNING: inconsistent lock state\n");
>  	print_kernel_ident();
> -	printk("---------------------------------\n");
> +	pr_warn("--------------------------------\n");
>  
>  	printk("inconsistent {%s} -> {%s} usage.\n",
>  		usage_str[prev_bit], usage_str[new_bit]);
> @@ -2425,10 +2425,10 @@ print_irq_inversion_bug(struct task_struct *curr,
>  		return 0;
>  
>  	printk("\n");
> -	printk("=========================================================\n");
> -	printk("[ INFO: possible irq lock inversion dependency detected ]\n");
> +	pr_warn("========================================================\n");
> +	pr_warn("WARNING: possible irq lock inversion dependency detected\n");
>  	print_kernel_ident();
> -	printk("---------------------------------------------------------\n");
> +	pr_warn("--------------------------------------------------------\n");
>  	printk("%s/%d just changed the state of lock:\n",
>  		curr->comm, task_pid_nr(curr));
>  	print_lock(this);
> @@ -3170,10 +3170,10 @@ print_lock_nested_lock_not_held(struct task_struct *curr,
>  		return 0;
>  
>  	printk("\n");
> -	printk("==================================\n");
> -	printk("[ BUG: Nested lock was not taken ]\n");
> +	pr_warn("==================================\n");
> +	pr_warn("WARNING: Nested lock was not taken\n");
>  	print_kernel_ident();
> -	printk("----------------------------------\n");
> +	pr_warn("----------------------------------\n");
>  
>  	printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
>  	print_lock(hlock);
> @@ -3383,10 +3383,10 @@ print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
>  		return 0;
>  
>  	printk("\n");
> -	printk("=====================================\n");
> -	printk("[ BUG: bad unlock balance detected! ]\n");
> +	pr_warn("=====================================\n");
> +	pr_warn("WARNING: bad unlock balance detected!\n");
>  	print_kernel_ident();
> -	printk("-------------------------------------\n");
> +	pr_warn("-------------------------------------\n");
>  	printk("%s/%d is trying to release lock (",
>  		curr->comm, task_pid_nr(curr));
>  	print_lockdep_cache(lock);
> @@ -3880,10 +3880,10 @@ print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
>  		return 0;
>  
>  	printk("\n");
> -	printk("=================================\n");
> -	printk("[ BUG: bad contention detected! ]\n");
> +	pr_warn("=================================\n");
> +	pr_warn("WARNING: bad contention detected!\n");
>  	print_kernel_ident();
> -	printk("---------------------------------\n");
> +	pr_warn("---------------------------------\n");
>  	printk("%s/%d is trying to contend lock (",
>  		curr->comm, task_pid_nr(curr));
>  	print_lockdep_cache(lock);
> @@ -4244,10 +4244,10 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
>  		return;
>  
>  	printk("\n");
> -	printk("=========================\n");
> -	printk("[ BUG: held lock freed! ]\n");
> +	pr_warn("=========================\n");
> +	pr_warn("WARNING: held lock freed!\n");
>  	print_kernel_ident();
> -	printk("-------------------------\n");
> +	pr_warn("-------------------------\n");
>  	printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
>  		curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
>  	print_lock(hlock);
> @@ -4302,11 +4302,11 @@ static void print_held_locks_bug(void)
>  		return;
>  
>  	printk("\n");
> -	printk("=====================================\n");
> -	printk("[ BUG: %s/%d still has locks held! ]\n",
> +	pr_warn("====================================\n");
> +	pr_warn("WARNING: %s/%d still has locks held!\n",
>  	       current->comm, task_pid_nr(current));
>  	print_kernel_ident();
> -	printk("-------------------------------------\n");
> +	pr_warn("------------------------------------\n");
>  	lockdep_print_held_locks(current);
>  	printk("\nstack backtrace:\n");
>  	dump_stack();
> @@ -4371,7 +4371,7 @@ void debug_show_all_locks(void)
>  	} while_each_thread(g, p);
>  
>  	printk("\n");
> -	printk("=============================================\n\n");
> +	pr_warn("=============================================\n\n");
>  
>  	if (unlock)
>  		read_unlock(&tasklist_lock);
> @@ -4401,10 +4401,10 @@ asmlinkage __visible void lockdep_sys_exit(void)
>  		if (!debug_locks_off())
>  			return;
>  		printk("\n");
> -		printk("================================================\n");
> -		printk("[ BUG: lock held when returning to user space! ]\n");
> +		pr_warn("================================================\n");
> +		pr_warn("WARNING: lock held when returning to user space!\n");
>  		print_kernel_ident();
> -		printk("------------------------------------------------\n");
> +		pr_warn("------------------------------------------------\n");
>  		printk("%s/%d is leaving the kernel with locks still held!\n",
>  				curr->comm, curr->pid);
>  		lockdep_print_held_locks(curr);
> @@ -4421,13 +4421,13 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
>  #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
>  	/* Note: the following can be executed concurrently, so be careful. */
>  	printk("\n");
> -	pr_err("===============================\n");
> -	pr_err("[ ERR: suspicious RCU usage.  ]\n");
> +	pr_warn("=============================\n");
> +	pr_warn("WARNING: suspicious RCU usage\n");
>  	print_kernel_ident();
> -	pr_err("-------------------------------\n");
> -	pr_err("%s:%d %s!\n", file, line, s);
> -	pr_err("\nother info that might help us debug this:\n\n");
> -	pr_err("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
> +	pr_warn("-----------------------------\n");
> +	printk("%s:%d %s!\n", file, line, s);
> +	printk("\nother info that might help us debug this:\n\n");
> +	printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
>  	       !rcu_lockdep_current_cpu_online()
>  			? "RCU used illegally from offline CPU!\n"
>  			: !rcu_is_watching()
> diff --git a/kernel/locking/rtmutex-debug.c b/kernel/locking/rtmutex-debug.c
> index 97ee9df32e0f..db4f55211b04 100644
> --- a/kernel/locking/rtmutex-debug.c
> +++ b/kernel/locking/rtmutex-debug.c
> @@ -102,10 +102,11 @@ void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
>  		return;
>  	}
>  
> -	printk("\n============================================\n");
> -	printk(  "[ BUG: circular locking deadlock detected! ]\n");
> -	printk("%s\n", print_tainted());
> -	printk(  "--------------------------------------------\n");
> +	pr_warn("\n");
> +	pr_warn("============================================\n");
> +	pr_warn("WARNING: circular locking deadlock detected!\n");
> +	pr_warn("%s\n", print_tainted());
> +	pr_warn("--------------------------------------------\n");
>  	printk("%s/%d is deadlocking current task %s/%d\n\n",
>  	       task->comm, task_pid_nr(task),
>  	       current->comm, task_pid_nr(current));
> -- 
> 2.5.2
>