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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2007-12-22 14:03:29 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-12-23 12:54:37 -0800
commitf16b34aa13e8c55085f346bcf07afb2312c56c0a (patch)
tree4fba40d99a5907694a1a1de8023f1431204f4f98 /drivers
parentcc295d0e95063809af31971e4aec1d809247f13b (diff)
lib: proportion: fix underflow in prop_norm_percpu()
Zhe Jiang noticed that its possible to underflow pl->events in prop_norm_percpu() when the value returned by percpu_counter_read() is less than the error on that read and the period delay > 1. In that case half might not trigger the batch increment and the value will be identical on the next iteration, causing the same half to be subtracted again and again. Fix this by rewriting the division as a single subtraction instead of a subtraction loop and using percpu_counter_sum() when the value returned by percpu_counter_read() is smaller than the error. The latter is still needed if we want pl->events to shrink properly in the error region. [akpm@linux-foundation.org: cleanups] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by: Jiang Zhe <zhe.jiang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
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