On Wed, 2 Jun 2010 15:26:52 -0700 Cory Maccarrone <darkstar6262@xxxxxxxxx> wrote: > On Wed, Jun 2, 2010 at 2:05 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, 29 May 2010 19:27:23 -0700 > > Cory Maccarrone <darkstar6262@xxxxxxxxx> wrote: > > > >> This change removes a BUG_ON for when interrupts are disabled > >> during an MMC request. __During boot, interrupts can be disabled > >> when a request is made, causing this bug to be triggered. __In reality, > >> there's no reason this should halt the kernel, as the driver has proved > >> reliable in spite of disabled interrupts, and additionally, there's > >> nothing in this code that would require interrupts to be enabled. > >> > >> Signed-off-by: Cory Maccarrone <darkstar6262@xxxxxxxxx> > >> --- > >> __drivers/mmc/host/omap.c | __ __1 - > >> __1 files changed, 0 insertions(+), 1 deletions(-) > >> > >> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c > >> index 2b28168..d98ddcf 100644 > >> --- a/drivers/mmc/host/omap.c > >> +++ b/drivers/mmc/host/omap.c > >> @@ -1157,7 +1157,6 @@ static void mmc_omap_start_request(struct mmc_omap_host *host, > >> __ __ __ mmc_omap_start_command(host, req->cmd); > >> __ __ __ if (host->dma_in_use) > >> __ __ __ __ __ __ __ omap_start_dma(host->dma_ch); > >> - __ __ BUG_ON(irqs_disabled()); > >> __} > >> > >> __static void mmc_omap_request(struct mmc_host *mmc, struct mmc_request *req) > > > > So we need to decide whether this should be backported into 2.6.34.x > > and perhaps earlier. > > > > For that decision we'll need to know the things you didn't tell us: > > Which drivers are affected? __Under which setups is it triggering? __Why > > aren't lots of people reporting "hey my kernel went BUG"? > > > > > > The only setup I've managed to make it trigger on is on the HTC Herald > during bootup when the driver is built into the kernel (mostly because > that's all I have). I believe it's related to the fact that on bootup > I get many timeout errors on "CMD5" while initializing the card. Each > CMD5 timeout triggers that bug (I changed it to a WARN_ON to get it to > boot in) due to the fact that part of the timeout code involves > sending the request again. With interrupts turned off, that BUG would > be triggered. > > I can't answer the question of why other people aren't reporting this > -- I know the CMD timeouts are fairly common with this driver, and > it's only within the last few kernel releases that their triggering > the BUG started happening. (I had only been able to test it because I > was carrying forward the MMC 16-bit patch I submitted a while ago > which only recently made it in. I'm not sure if that's related or > not, but I need that to use the MMC-OMAP on herald.) Do you have one of these BUG_ON() traces handy, so we can perhaps see where local interrupts got disabled? > I imagine a better solution to this would be to fix the timeout issues > so the repeated requests aren't a problem. But any hardware bugs that > cause a timeout during boot would cause this bug to be triggered, > which is why I'm proposing removing the BUG_ON entirely (since > everything seems to work fine anyway). > > I don't know why interrupts are disabled at this point, but my limited > googling around leads me to believe the recent LOCKDEP work may be the > cause. I couldn't find enough information on that to know for sure > though. I do know that the bug no longer triggers after the card > initializes successfully (and presumably interrupts re-enable). > > My guess is that since other people aren't reporting this problem, > it's not hugely important to backport. A better question in that case > would be why am I seeing it? I don't understand why interrupts would > be disabled at this point in bootup. > Yes, before removing the BUG_ON() it would be most helpful to understand why it was added. It was added by : commit abfbe5f7854a083ca324282bf7e39f10bc438313 : Author: Juha Yrjola <juha.yrjola@xxxxxxxxxxxxx> : AuthorDate: Wed Mar 26 16:08:57 2008 -0400 : Commit: Pierre Ossman <drzeus@xxxxxxxxx> : CommitDate: Fri Apr 18 20:05:28 2008 +0200 : : MMC: OMAP: Introduce new multislot structure and change driver to use it : : Introduce new MMC multislot structure and change driver to use it. : : Note that MMC clocking is now enabled in mmc_omap_select_slot() : and disabled in mmc_omap_release_slot(). : : Signed-off-by: Juha Yrjola <juha.yrjola@xxxxxxxxxxxxx> : Signed-off-by: Jarkko Lavinen <jarkko.lavinen@xxxxxxxxx> : Signed-off-by: Carlos Eduardo Aguiar <carlos.aguiar@xxxxxxxxxxx> : Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> : Signed-off-by: Pierre Ossman <drzeus@xxxxxxxxx> Hopefully the email still works.. Juha, do you recall why you added the BUG_ON(irqs_disabled()) to mmc_omap_start_request()? -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
