Messages in this thread | | | Date | Thu, 27 Jan 2022 06:59:50 +0100 | Subject | Re: [PATCH] mm/util.c: Make kvfree() safe for calling while holding spinlocks | From | Manfred Spraul <> |
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Hi Andrew,
On 1/27/22 03:53, Andrew Morton wrote: > On Wed, 22 Dec 2021 20:48:28 +0100 Manfred Spraul <manfred@colorfullife.com> wrote: > >> One codepath in find_alloc_undo() calls kvfree() while holding a spinlock. >> Since vfree() can sleep this is a bug. >> >> Previously, the code path used kfree(), and kfree() is safe to be called >> while holding a spinlock. >> >> Minghao proposed to fix this by updating find_alloc_undo(). >> >> Alternate proposal to fix this: Instead of changing find_alloc_undo(), >> change kvfree() so that the same rules as for kfree() apply: >> Having different rules for kfree() and kvfree() just asks for bugs. >> >> Disadvantage: Releasing vmalloc'ed memory will be delayed a bit. > I know we've been around this loop a bunch of times and deferring was > considered. But I forget the conclusion. IIRC, mhocko was involved?
I do not remember a mail from mhocko.
Shakeel proposed to use the approach from Chi.
Decision: https://marc.info/?l=linux-kernel&m=164132032717757&w=2
With Reviewed-by:
https://marc.info/?l=linux-kernel&m=164132744522325&w=2 >> --- a/mm/util.c >> +++ b/mm/util.c >> @@ -610,12 +610,12 @@ EXPORT_SYMBOL(kvmalloc_node); >> * It is slightly more efficient to use kfree() or vfree() if you are certain >> * that you know which one to use. >> * >> - * Context: Either preemptible task context or not-NMI interrupt. >> + * Context: Any context except NMI interrupt. >> */ >> void kvfree(const void *addr) >> { >> if (is_vmalloc_addr(addr)) >> - vfree(addr); >> + vfree_atomic(addr); >> else >> kfree(addr); >> }
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