On Wed, 26 Oct 2016 19:09:51 +0100 Will Deacon <[email protected]> wrote:
> On Tue, Oct 25, 2016 at 11:36:44AM -0700, Daniel Mentz wrote: > > gen_pool_alloc_algo() iterates over the chunks of a pool trying to find > > a contiguous block of memory that satisfies the allocation request. > > > > The shortcut > > > > if (size > atomic_read(&chunk->avail)) > > continue; > > > > makes the loop skip over chunks that do not have enough bytes left to > > fulfill the request. There are two situations, though, where an > > allocation might still fail: > > > > (1) The available memory is not contiguous, i.e. the request cannot be > > fulfilled due to external fragmentation. > > > > (2) A race condition. Another thread runs the same code concurrently and > > is quicker to grab the available memory. > > > > In those situations, the loop calls pool->algo() to search the entire > > chunk, and pool->algo() returns some value that is >= end_bit to > > indicate that the search failed. This return value is then assigned to > > start_bit. The variables start_bit and end_bit describe the range that > > should be searched, and this range should be reset for every chunk that > > is searched. Today, the code fails to reset start_bit to 0. As a > > result, prefixes of subsequent chunks are ignored. Memory allocations > > might fail even though there is plenty of room left in these prefixes of > > those other chunks. > > Please add a CC stable. You sure? The changelog doesn't describe the end-user impacts very well (it should always do so, please) but I'm thinking "little impact"? > With that: > > Acked-by: Will Deacon <[email protected]> > > Will
