Messages in this thread | | | Date | Wed, 2 Mar 2022 14:38:09 +0800 | Subject | Re: [PATCH v4 2/2] io_uring: Add support for napi_busy_poll | From | Hao Xu <> |
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On 3/2/22 14:27, Hao Xu wrote: > > On 3/2/22 04:06, Olivier Langlois wrote: >> On Wed, 2022-03-02 at 02:31 +0800, Hao Xu wrote: >>>> + ne = kmalloc(sizeof(*ne), GFP_NOWAIT); >>>> + if (!ne) >>>> + goto out; >>> IMHO, we need to handle -ENOMEM here, I cut off the error handling >>> when >>> >>> I did the quick coding. Sorry for misleading. >> If you are correct, I would be shocked about this. >> >> I did return in my 'Linux Device Drivers' book and nowhere it is >> mentionned that the kmalloc() can return something else than a pointer >> >> No mention at all about the return value >> >> in man page: >> https://www.kernel.org/doc/htmldocs/kernel-api/API-kmalloc.html >> API doc: >> >> https://www.kernel.org/doc/html/latest/core-api/mm-api.html?highlight=kmalloc#c.kmalloc >> >> >> header file: >> https://elixir.bootlin.com/linux/latest/source/include/linux/slab.h#L522 >> >> I did browse into the kmalloc code. There is a lot of paths to cover >> but from preliminary reading, it pretty much seems that kmalloc only >> returns a valid pointer or NULL... >> >> /** >> * kmem_cache_alloc - Allocate an object >> * @cachep: The cache to allocate from. >> * @flags: See kmalloc(). >> * >> * Allocate an object from this cache. The flags are only relevant >> * if the cache has no available objects. >> * >> * Return: pointer to the new object or %NULL in case of error >> */ >> /** >> * __do_kmalloc - allocate memory >> * @size: how many bytes of memory are required. >> * @flags: the type of memory to allocate (see kmalloc). >> * @caller: function caller for debug tracking of the caller >> * >> * Return: pointer to the allocated memory or %NULL in case of error >> */ >> >> I'll need someone else to confirm about possible kmalloc() return >> values with perhaps an example >> >> I am a bit skeptic that something special needs to be done here... >> >> Or perhaps you are suggesting that io_add_napi() returns an error code >> when allocation fails. > This is what I mean. >> >> as done here: >> https://elixir.bootlin.com/linux/latest/source/arch/alpha/kernel/core_marvel.c#L867 >> >> >> If that is what you suggest, what would this info do for the caller? >> >> IMHO, it wouldn't help in any way... > > Hmm, I'm not sure, you're probably right based on that ENOMEM here > shouldn't > > fail the arm poll, but we wanna do it, we can do something like what > we do for ^---but if we wanna do it
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