Martin Husemann <mar...@duskware.de> writes: > On Wed, Nov 11, 2020 at 08:26:45AM -0500, Greg Troxel wrote: >> > LOCK(st); >> > size_t n, max_n = st->num_items; >> > some_state_item **tmp_list = >> > kmem_intr_alloc(max_n * sizeof(*tmp_list)); >> >> kmem_intr_alloc takes a flag, and it seems that you need to pass >> KM_NOSLEEP, as blocking for memory in softint context is highly unlikely >> to be the right thing. > > Yes, and of course the real code has that (and works). It's just that > - memoryallocators(9) does not cover this case > - kmem_intr_alloc(9) is kinda deprecated - quoting the man page: > > These routines are for the special cases. Normally, > pool_cache(9) should be used for memory allocation from interrupt > context. > > but how would I use pool_cache(9) here?
Not deprecated, but for "special cases". I think needing a possibly-big variable-size chunk of memory at interrupt time is special. You would use pool_cache by being able to use a fixed-sized object. But it seems that's not how the situation is. I think memoryallocators(9) could use some spiffing up; it (on 9) says kmem(9) cannot be used from interrupt context. The central hard problem is orthogonal, though: if you don't pre-allocate, you have to choose between waiting and copying with failure.
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