Hello, On Fri, Feb 08, 2013 at 10:09:13PM +0000, Hefty, Sean wrote: > > Used to wrap cyclic @start. Can be replaced with max(next, 0). > > Note that this type of cyclic allocation using idr is buggy. These > > are prone to spurious -ENOSPC failure after the first wraparound. > > The replacement code looks fine, but can you explain why the use is buggy? So, if you want a cyclic allocation, the allocation should be tried in [start, END) and then [0, start); otherwise, after the allocation wraps for the first time, as the closer the starting point gets to END, the chance of not finding a vacant slot in [start, END) goes higher. When @start equals END - 1 for the second time, if the first END - 1 allocation is still around, you'll get -ENOSPC. In practice, I don't think anyone is hitting this. idr has always been horribly broken when it reaches higher range (> 1<<30 on 64bit) so things would have broken even before the first wraparound. It still is a theoretical possibility which may trigger if idr is used for, say, ipc messages or storage commands. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
