On Fri, 22 Feb 2013 14:21:58 -0800 Tejun Heo <t...@kernel.org> wrote:
> Hello, Andrew. > > On Fri, Feb 22, 2013 at 2:16 PM, Andrew Morton > <a...@linux-foundation.org> wrote: > > Given that this code is performing allocations under > > spin_lock_irqsave(), it should be using idr_preload()/idr_preload_end() > > (and perhaps even a repeat loop around those) to make the allocations > > more reliable. > > It's already using preload so GFP_NOWAIT is enough to guarantee > GFP_KERNEL level allocation. > Not "guarantee". - idr_preload() might fail. It is a design error that idr_preload() returns void - it should do what radix_tree_preload() does. - even if idr_preload() completed the preload, an interrupt might come in and its handler might drain this cpu's preload pool. This all sounds like crazy will-never-happen stuff. That's what I thought about the radix-tree code when used for pagecache. But under extreme worloads, the cant-happens kept on happening, which is how all that funky preload/preempt-disable stuff occurred. It would be more robust still if the per-cpu preload magazines were per-radixtree and per-idr, rather than kernel-wide. That would reduce the risk of interrupt-time stealing. Or make foo_preload() return with interrupts disabled rather than jsut preempt_disable(). -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
