Messages in this thread | | | Date | Mon, 17 Nov 2008 10:28:46 +0100 | From | Nicolas Ferre <> | Subject | Re: [patch 2.6.28-rc2] at91_mci: workaround lockdep |
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David Brownell : > 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.) > > Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> --- > An alternate fix might be to have ARM dcache mmap locking save and restore > the IRQ flags ... but there are several such "can't run with IRQs disabled" > restrictions scattered through that code, with no rationales commented. Or > stop lockdep from mucking with IRQ flags; probably not any time soon! > > So for now, this seems to be the best "solution" available... > > drivers/mmc/host/Kconfig | 1 + > drivers/mmc/host/at91_mci.c | 3 +-- > 2 files changed, 2 insertions(+), 2 deletions(-) > > --- a/drivers/mmc/host/Kconfig > +++ b/drivers/mmc/host/Kconfig > @@ -99,6 +99,7 @@ config MMC_AU1X > config MMC_AT91 > tristate "AT91 SD/MMC Card Interface support" > depends on ARCH_AT91 > + depends on LOCKDEP=n > help > This selects the AT91 MCI controller. > > --- a/drivers/mmc/host/at91_mci.c > +++ b/drivers/mmc/host/at91_mci.c > @@ -1081,8 +1081,7 @@ static int __init at91_mci_probe(struct > * Allocate the MCI interrupt > */ > host->irq = platform_get_irq(pdev, 0); > - ret = request_irq(host->irq, at91_mci_irq, IRQF_SHARED, > - mmc_hostname(mmc), host); > + ret = request_irq(host->irq, at91_mci_irq, 0, mmc_hostname(mmc), host); > if (ret) { > dev_dbg(&pdev->dev, "request MCI interrupt failed\n"); > goto fail0; >
Thanks, regards, -- Nicolas Ferre
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