Messages in this thread | | | Subject | Re: [patch 2.6.28-rc2] at91_mci: workaround lockdep | From | Peter Zijlstra <> | Date | Tue, 28 Oct 2008 18:04:02 +0100 |
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On Mon, 2008-10-27 at 14:26 -0700, David Brownell wrote: > From: David Brownell <dbrownell@users.sourceforge.net> > > Lockdep reported a problem in the at91_mci driver ... in this case, the > issue is with lockdep, not with the driver. A trimmed stack dump, from > trying to boot with root on MMC, shows: > > WARNING: at kernel/lockdep.c:2195 trace_hardirqs_on_caller+0xf4/0x170() > Modules linked in: > [<c005bc98>] (trace_hardirqs_on+0x0/0x18) from [<c0213bf4>] (_spin_unlock_irq+0x2c/0x3c) > [<c0213bc8>] (_spin_unlock_irq+0x0/0x3c) from [<c0029a88>] (flush_dcache_page+0x114/0x144) > [<c0029974>] (flush_dcache_page+0x0/0x144) from [<c019b034>] (at91_mci_irq+0x150/0x414) > [<c019aee4>] (at91_mci_irq+0x0/0x414) from [<c0066c5c>] (handle_IRQ_event+0x2c/0x6c) > [<c0066c30>] (handle_IRQ_event+0x0/0x6c) from [<c0068a60>] (handle_level_irq+0x108/0x124) > [<c0068958>] (handle_level_irq+0x0/0x124) from [<c0022064>] (__exception_text_start+0x64/0x90) > > When __flush_dcache_aliases() returns -- inlined into flush_dcache_page(), > above -- it re-enables IRQs ... since that evidently may only be called with > IRQs enabled. That's OK since the (unshared) IRQ handler doesn't ask for IRQs > to be disabled. Except ... that lockdep went and disabled them, then went on > to complains about the breakage *it* caused! > > Workaround: depend on LOCKDEP=n ... and for paranoia, disable IRQF_SHARED > for this interrupt. (At the hardware level, this is dedicated to MCI, so > there's never a need for multiple handlers.)
In all previous such cases it was deemed the IRQ handler should deal with whatever it gets.
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