Re: [PATCH] mm/util.c: Make kvfree() safe for calling while holding spinlocks

Hello Vasily,

On 12/23/21 08:21, Vasily Averin wrote:

I would prefer to release memory ASAP if it's possible. What do you think about this change? --- a/mm/util.c +++ b/mm/util.c @@ -614,9 +614,12 @@ EXPORT_SYMBOL(kvmalloc_node); */ void kvfree(const void *addr) {

•   if (is_vmalloc_addr(addr))
  

•           vfree(addr);
  

•   else
  

•   if (is_vmalloc_addr(addr)) {
  

•           if (in_atomic())
  

•                   vfree_atomic();
  

•           else
  

•                   vfree(addr);
  

•   } else
             kfree(addr);
  

  } EXPORT_SYMBOL(kvfree);

Unfortunately this cannot work:

/*

• Are we running in atomic context?  WARNING: this macro cannot
• always detect atomic context; in particular, it cannot know about
• held spinlocks in non-preemptible kernels.  Thus it should not be
• used in the general case to determine whether sleeping is possible.
• Do not use in_atomic() in driver code.

*/ #define in_atomic()     (preempt_count() != 0)

--

Manfred