Subject: linux-next: manual merge of the akpm-current tree with the printk tree

From: Stephen Rothwell <[email-masked]>
Date: Wed, 23 Jun 2021 21:12:36 +1000

Hi all,

Today's linux-next merge of the akpm-current tree got a conflict in:

  lib/dump_stack.c

between commit:

  766c268bc6d3 ("lib/dump_stack: move cpu lock to printk.c")

from the printk tree and commit:

  250da8183544 ("printk: introduce dump_stack_lvl()")

from the akpm-current tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging.  You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.

-- 
Cheers,
Stephen Rothwell

diff --cc lib/dump_stack.c
index 5ebf4375fa8c,586e3f2c6a15..000000000000
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@@ -84,16 -84,56 +84,22 @@@ static void __dump_stack(const char *lo
   *
   * Architectures can override this implementation by implementing its own.
   */
- asmlinkage __visible void dump_stack(void)
 -#ifdef CONFIG_SMP
 -static atomic_t dump_lock = ATOMIC_INIT(-1);
 -
+ asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
  {
  	unsigned long flags;
 -	int was_locked;
 -	int old;
 -	int cpu;
  
  	/*
  	 * Permit this cpu to perform nested stack dumps while serialising
  	 * against other CPUs
  	 */
 -retry:
 -	local_irq_save(flags);
 -	cpu = smp_processor_id();
 -	old = atomic_cmpxchg(&dump_lock, -1, cpu);
 -	if (old == -1) {
 -		was_locked = 0;
 -	} else if (old == cpu) {
 -		was_locked = 1;
 -	} else {
 -		local_irq_restore(flags);
 -		/*
 -		 * Wait for the lock to release before jumping to
 -		 * atomic_cmpxchg() in order to mitigate the thundering herd
 -		 * problem.
 -		 */
 -		do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
 -		goto retry;
 -	}
 -
 -	__dump_stack(log_lvl);
 -
 -	if (!was_locked)
 -		atomic_set(&dump_lock, -1);
 -
 -	local_irq_restore(flags);
 -}
 -#else
 -asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
 -{
 +	printk_cpu_lock_irqsave(flags);
- 	__dump_stack();
+ 	__dump_stack(log_lvl);
 +	printk_cpu_unlock_irqrestore(flags);
  }
 -#endif
+ EXPORT_SYMBOL(dump_stack_lvl);
+ 
+ asmlinkage __visible void dump_stack(void)
+ {
+ 	dump_stack_lvl(KERN_DEFAULT);
+ }
  EXPORT_SYMBOL(dump_stack);