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According to Kevin Corry: > Article: 452202 of lists.linux.kernel > From: Kevin Corry <kevcorry@us.ibm.com> > Date: Mon, 1 Mar 2004 14:00:50 -0600 > Newsgroups: lists.linux.kernel > Approved: news@news.cistron.nl > > The queue-congestion-dm-implementation patch in 2.6.4-rc1-mm1 (included below) > allows a DM device to query the lower-level device(s) during the > queue-congestion APIs. However, it must wait on an internal semaphore > (md->lock) before passing the call down to the lower-level devices. The > problem is that the higher-level caller is holding a spinlock at the same > time. Here is one such stack-trace I have been seeing: > > Debug: sleeping function called from invalid context at include/linux/ > rwsem.h:43 > in_atomic():1, irqs_disabled():0 > Call Trace: > [<c012456b>] __might_sleep+0xab/0xd0 > [<c03a0771>] dm_any_congested+0x21/0x60 Is there any way to reproduce this? I turned on spinlock and sleep-spinlock debugging and did lots of I/O but I don't see it. > I'm not sure how to fix this (or how serious a problem it is)...I'm just > throwing this out there for discussion. Well bdi_write_congested() is racy, ofcourse, so in theory a call to make_request() could be made which can block (and for dm, locks the same semaphore) - so this can happen anyway. Only the chance of it is much lower. I'm not sure how bad it is. Changing down_read() in dm_any_congested to down_read_trylock() would probably fix it for bdi_*_congested(). If you can tell me how to reproduce it I can try a few things.. Mike. - 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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