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authorDaniel Mentz <danielmentz@google.com>2016-10-27 17:46:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-27 18:43:43 -0700
commit62e931fac45b17c2a42549389879411572f75804 (patch)
treea66bc11e84beee712de9fd2d4711d722db0edd80 /drivers/hwmon/jc42.c
parent89a2848381b5fcd9c4d9c0cd97680e3b28730e31 (diff)
downloadlinux-62e931fac45b17c2a42549389879411572f75804.tar.bz2
lib/genalloc.c: start search from start of chunk
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. Fixes: 7f184275aa30 ("lib, Make gen_pool memory allocator lockless") Link: http://lkml.kernel.org/r/1477420604-28918-1-git-send-email-danielmentz@google.com Signed-off-by: Daniel Mentz <danielmentz@google.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/hwmon/jc42.c')
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