From mboxrd@z Thu Jan 1 00:00:00 1970 From: benh@kernel.crashing.org (Benjamin Herrenschmidt) Date: Tue, 08 Oct 2013 07:10:56 +1100 Subject: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern In-Reply-To: <20131007180111.GC2481@htj.dyndns.org> References: <1380840585.3419.50.camel@bwh-desktop.uk.level5networks.com> <20131004082920.GA4536@dhcp-26-207.brq.redhat.com> <1380922156.3214.49.camel@bwh-desktop.uk.level5networks.com> <20131005142054.GA11270@dhcp-26-207.brq.redhat.com> <1381009586.645.141.camel@pasglop> <20131006060243.GB28142@dhcp-26-207.brq.redhat.com> <1381040386.645.143.camel@pasglop> <20131006071027.GA29143@dhcp-26-207.brq.redhat.com> <20131007180111.GC2481@htj.dyndns.org> Message-ID: <1381176656.645.171.camel@pasglop> On Mon, 2013-10-07@14:01 -0400, Tejun Heo wrote: > I don't think the same race condition would happen with the loop. The > problem case is where multiple msi(x) allocation fails completely > because the global limit went down before inquiry and allocation. In > the loop based interface, it'd retry with the lower number. > > As long as the number of drivers which need this sort of adaptive > allocation isn't too high and the common cases can be made simple, I > don't think the "complex" part of interface is all that important. > Maybe we can have reserve / cancel type interface or just keep the > loop with more explicit function names (ie. try_enable or something > like that). I'm thinking a better API overall might just have been to request individual MSI-X one by one :-) We want to be able to request an MSI-X at runtime anyway ... if I want to dynamically add a queue to my network interface, I want it to be able to pop a new arbitrary MSI-X. And we don't want to lock drivers into contiguous MSI-X sets either. And for the cleanup ... well that's what the "pcim" functions are for, we can just make MSI-X variants. Ben.