Messages in this thread | | | Date | Mon, 03 Mar 2008 18:58:32 +0100 | From | Stefan Richter <> | Subject | Re: [PATCH] firewire: reread config ROM when device reset the bus |
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Kristian Høgsberg wrote: > On Mon, Mar 3, 2008 at 11:51 AM, Stefan Richter > <stefanr@s5r6.in-berlin.de> wrote: > ... >> Maybe I should rather use fw-device.c::idr_rwsem instead of device.sem, >> to have better control over who takes the mutex when. Could also be a >> new dedicated mutex but we don't want to end up with too many of them... >> Do you have an opinion? > > Using the struct device mutex is fine, and it parallelizes better than > the global idr_mutex (FWIW). The only concern I have there is that > the device core structs seem to change now and then, and it's not > clear what is implementation details and what is exported for drivers > to use (eg the subsystem sem).
This may be more of a concern to anybody who wanted to change the driver core internals and might be unsure what to do with those three dev->sem taking sites which I added; not so much a concern from the firewire driver maintenance POV.
OTOH, contention for idr_rwsem is low and there can be multiple readers of course. The most time consuming thing that could happen would be waiting for GFP_KERNEL allocations of new IDR tree leaves. And maybe having the dev->sem in a cacheline but idr_rwsem not is probably not a concern for the stuff that the writer and the two readers of the ROM cache do.
Ah, wait, there is a 3rd reader: sbp2_probe's sbp2_scan_unit_dir. So, using dev->sem is actually the nicest way for now. -- Stefan Richter -=====-==--- --== ---== http://arcgraph.de/sr/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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