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

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